1GPSD_JSON(5) GPSD Documentation GPSD_JSON(5)
2
6 gpsd_json - gpsd request/response protocol
7
9 gpsd is a service daemon that can be used to monitor GPSes, DGPS
10 receivers, Marine AIS broadcasts, and various other location-related
11 and kinematic sensors.
12 Clients may communicate with gpsd via textual requests and responses
14 over a socket. It is a bad idea for applications to speak the protocol
15 directly: rather, they should use the libgps client library (for C;
16 bindings also exist for other languages) and take appropriate care to
17 conditionalize their code on the major and minor protocol version
18 symbols.
19 The GPSD protocol is built on top of JSON, JavaScript Object Notation,
21 as specified in RFC 7159: The JavaScript Object Notation (JSON) Data
22 Interchange Format. GPSD's use of JSON is restricted in some ways that
23 make parsing it in fixed-extent languages (such as C) easier.
24 A request line is introduced by "?" and may include multiple commands.
26 Commands begin with a command identifier, followed either by a
27 terminating ';' or by an equal sign "=" and a JSON object treated as an
28 argument. Any ';' or newline indication (either LF or CR-LF) after the
29 end of a command is ignored. All request lines must be composed of
30 US-ASCII characters and may be no more than 80 characters in length,
31 exclusive of the trailing newline.
32 Responses are JSON objects all of which have a "class" attribute the
34 value of which is either the name of the invoking command. There are
35 reports (including but not limited to as "TPV", "SKY", "DEVICE", and
36 "ERROR") which are not direct responses to commands.
37 The order of JSON attributes within a response object is never
39 significant, and you may specify attributes in commands in any order.
40 Responses never contain the special JSON value null; instead,
41 attributes with empty or undefined values are omitted. The length limit
42 for responses and reports is 1536 characters, including trailing
43 newline; longer responses will be truncated, so client code must be
44 prepared for the possibility of invalid JSON fragments.
45 In JSON reports, if an attribute is present only if the parent
47 attribute is present or has a particular range, then the parent
48 attribute is emitted first.
49 There is one constraint on the order in which attributes will be
51 omitted. If an optional attribute is present only when a parent
52 attribute has a specified value or range of values, the parent
53 attribute will be emitted first to make parsing easier.
54 The next subsection section documents the core GPSD protocol.
56 Extensions are documented in the following subsections. The extensions
57 may not be supported in your gpsd instance if it has been compiled with
58 a restricted feature set.
59
61 Here are the core-protocol responses:
62 TPV
64 A TPV object is a time-position-velocity report. The "class" and
65 "mode" fields will reliably be present. The "mode" field will be
66 emitted before optional fields that may be absent when there is no
67 fix. Error estimates will be emitted after the fix components
68 they're associated with. Others may be reported or not depending on
69 the fix quality.
70 Table 1. TPV object
72 ┌───────┬─────────┬─────────┬──────────────────┐
73 │Name │ Always? │ Type │ Description │
74 ├───────┼─────────┼─────────┼──────────────────┤
75 │class │ Yes │ string │ Fixed: "TPV" │
76 ├───────┼─────────┼─────────┼──────────────────┤
77 │device │ No │ string │ Name of │
78 │ │ │ │ originating │
79 │ │ │ │ device. │
80 ├───────┼─────────┼─────────┼──────────────────┤
81 │status │ No │ numeric │ GPS status: %d, │
82 │ │ │ │ 2=DGPS fix, │
83 │ │ │ │ otherwise not │
84 │ │ │ │ present. │
85 ├───────┼─────────┼─────────┼──────────────────┤
86 │mode │ Yes │ numeric │ NMEA mode: %d, │
87 │ │ │ │ 0=no mode value │
88 │ │ │ │ yet seen, 1=no │
89 │ │ │ │ fix, 2=2D, 3=3D. │
90 ├───────┼─────────┼─────────┼──────────────────┤
91 │time │ No │ string │ Time/date stamp │
92 │ │ │ │ in ISO8601 │
93 │ │ │ │ format, UTC. May │
94 │ │ │ │ have a │
95 │ │ │ │ fractional │
96 │ │ │ │ part of up to │
97 │ │ │ │ .001sec │
98 │ │ │ │ precision. May │
99 │ │ │ │ be absent if │
100 │ │ │ │ mode │
101 │ │ │ │ is not 2 │
102 │ │ │ │ or 3. │
103 ├───────┼─────────┼─────────┼──────────────────┤
104 │ept │ No │ numeric │ Estimated │
105 │ │ │ │ timestamp error │
106 │ │ │ │ (%f, seconds, │
107 │ │ │ │ 95% confidence). │
108 │ │ │ │ Present │
109 │ │ │ │ if time is │
110 │ │ │ │ present. │
111 ├───────┼─────────┼─────────┼──────────────────┤
112 │lat │ No │ numeric │ Latitude in │
113 │ │ │ │ degrees: +/- │
114 │ │ │ │ signifies │
115 │ │ │ │ North/South. │
116 │ │ │ │ Present │
117 │ │ │ │ when │
118 │ │ │ │ mode is 2 or 3. │
119 ├───────┼─────────┼─────────┼──────────────────┤
120 │lon │ No │ numeric │ Longitude in │
121 │ │ │ │ degrees: +/- │
122 │ │ │ │ signifies │
123 │ │ │ │ East/West. │
124 │ │ │ │ Present │
125 │ │ │ │ when │
126 │ │ │ │ mode is 2 or 3. │
127 ├───────┼─────────┼─────────┼──────────────────┤
128 │alt │ No │ numeric │ Altitude in │
129 │ │ │ │ meters. Present │
130 │ │ │ │ if mode is 3. │
131 ├───────┼─────────┼─────────┼──────────────────┤
132 │epx │ No │ numeric │ Longitude error │
133 │ │ │ │ estimate in │
134 │ │ │ │ meters, 95% │
135 │ │ │ │ confidence. │
136 │ │ │ │ Present │
137 │ │ │ │ if mode │
138 │ │ │ │ is 2 or 3 and │
139 │ │ │ │ DOPs can be │
140 │ │ │ │ calculated from │
141 │ │ │ │ the satellite │
142 │ │ │ │ view. │
143 ├───────┼─────────┼─────────┼──────────────────┤
144 │epy │ No │ numeric │ Latitude error │
145 │ │ │ │ estimate in │
146 │ │ │ │ meters, 95% │
147 │ │ │ │ confidence. │
148 │ │ │ │ Present │
149 │ │ │ │ if mode │
150 │ │ │ │ is 2 or 3 and │
151 │ │ │ │ DOPs can be │
152 │ │ │ │ calculated from │
153 │ │ │ │ the satellite │
154 │ │ │ │ view. │
155 ├───────┼─────────┼─────────┼──────────────────┤
156 │epv │ No │ numeric │ Estimated │
157 │ │ │ │ vertical error │
158 │ │ │ │ in meters, 95% │
159 │ │ │ │ confidence. │
160 │ │ │ │ Present │
161 │ │ │ │ if mode │
162 │ │ │ │ is 3 and DOPs │
163 │ │ │ │ can be │
164 │ │ │ │ calculated from │
165 │ │ │ │ the satellite │
166 │ │ │ │ view. │
167 ├───────┼─────────┼─────────┼──────────────────┤
168 │track │ No │ numeric │ Course over │
169 │ │ │ │ ground, degrees │
170 │ │ │ │ from true north. │
171 ├───────┼─────────┼─────────┼──────────────────┤
172 │speed │ No │ numeric │ Speed over │
173 │ │ │ │ ground, meters │
174 │ │ │ │ per second. │
175 ├───────┼─────────┼─────────┼──────────────────┤
176 │climb │ No │ numeric │ Climb (positive) │
177 │ │ │ │ or sink │
178 │ │ │ │ (negative) rate, │
179 │ │ │ │ meters per │
180 │ │ │ │ second. │
181 ├───────┼─────────┼─────────┼──────────────────┤
182 │epd │ No │ numeric │ Direction error │
183 │ │ │ │ estimate in │
184 │ │ │ │ degrees, 95% │
185 │ │ │ │ confidence. │
186 ├───────┼─────────┼─────────┼──────────────────┤
187 │eps │ No │ numeric │ Speed error │
188 │ │ │ │ estinmate in │
189 │ │ │ │ meters/sec, 95% │
190 │ │ │ │ confidence. │
191 ├───────┼─────────┼─────────┼──────────────────┤
192 │epc │ No │ numeric │ Climb/sink error │
193 │ │ │ │ estimate in │
194 │ │ │ │ meters/sec, 95% │
195 │ │ │ │ confidence. │
196 └───────┴─────────┴─────────┴──────────────────┘
197 When the C client library parses a response of this kind, it will
198 assert validity bits in the top-level set member for each field
199 actually received; see gps.h for bitmask names and values.
200 Here's an example:
202 {"class":"TPV","device":"/dev/pts/1",
204 "time":"2005-06-08T10:34:48.283Z","ept":0.005,
205 "lat":46.498293369,"lon":7.567411672,"alt":1343.127,
206 "eph":36.000,"epv":32.321,
207 "track":10.3788,"speed":0.091,"climb":-0.085,"mode":3}
208 SKY
210 A SKY object reports a sky view of the GPS satellite positions. If
211 there is no GPS device available, or no skyview has been reported
212 yet, only the "class" field will reliably be present.
213 Table 2. SKY object
215 ┌───────────┬─────────┬─────────┬──────────────────┐
216 │Name │ Always? │ Type │ Description │
217 ├───────────┼─────────┼─────────┼──────────────────┤
218 │class │ Yes │ string │ Fixed: "SKY" │
219 ├───────────┼─────────┼─────────┼──────────────────┤
220 │device │ No │ string │ Name of │
221 │ │ │ │ originating │
222 │ │ │ │ device │
223 ├───────────┼─────────┼─────────┼──────────────────┤
224 │time │ No │ numeric │ Time/date stamp │
225 │ │ │ │ in ISO8601 │
226 │ │ │ │ format, UTC. May │
227 │ │ │ │ have a │
228 │ │ │ │ fractional │
229 │ │ │ │ part of up to │
230 │ │ │ │ .001sec │
231 │ │ │ │ precision. │
232 ├───────────┼─────────┼─────────┼──────────────────┤
233 │xdop │ No │ numeric │ Longitudinal │
234 │ │ │ │ dilution of │
235 │ │ │ │ precision, a │
236 │ │ │ │ dimensionless │
237 │ │ │ │ factor │
238 │ │ │ │ which should be │
239 │ │ │ │ multiplied by a │
240 │ │ │ │ base UERE to get │
241 │ │ │ │ an error │
242 │ │ │ │ estimate. │
243 ├───────────┼─────────┼─────────┼──────────────────┤
244 │ydop │ No │ numeric │ Latitudinal │
245 │ │ │ │ dilution of │
246 │ │ │ │ precision, a │
247 │ │ │ │ dimensionless │
248 │ │ │ │ factor │
249 │ │ │ │ which should be │
250 │ │ │ │ multiplied by a │
251 │ │ │ │ base UERE to get │
252 │ │ │ │ an error │
253 │ │ │ │ estimate. │
254 ├───────────┼─────────┼─────────┼──────────────────┤
255 │vdop │ No │ numeric │ Altitude │
256 │ │ │ │ dilution of │
257 │ │ │ │ precision, a │
258 │ │ │ │ dimensionless │
259 │ │ │ │ factor │
260 │ │ │ │ which should be │
261 │ │ │ │ multiplied by a │
262 │ │ │ │ base UERE to get │
263 │ │ │ │ an error │
264 │ │ │ │ estimate. │
265 ├───────────┼─────────┼─────────┼──────────────────┤
266 │tdop │ No │ numeric │ Time dilution of │
267 │ │ │ │ precision, a │
268 │ │ │ │ dimensionless │
269 │ │ │ │ factor │
270 │ │ │ │ which should be │
271 │ │ │ │ multiplied by a │
272 │ │ │ │ base UERE to get │
273 │ │ │ │ an error │
274 │ │ │ │ estimate. │
275 ├───────────┼─────────┼─────────┼──────────────────┤
276 │hdop │ No │ numeric │ Horizontal │
277 │ │ │ │ dilution of │
278 │ │ │ │ precision, a │
279 │ │ │ │ dimensionless │
280 │ │ │ │ factor │
281 │ │ │ │ which should be │
282 │ │ │ │ multiplied by a │
283 │ │ │ │ base UERE to get │
284 │ │ │ │ a circular │
285 │ │ │ │ error estimate. │
286 ├───────────┼─────────┼─────────┼──────────────────┤
287 │pdop │ No │ numeric │ Spherical │
288 │ │ │ │ dilution of │
289 │ │ │ │ precision, a │
290 │ │ │ │ dimensionless │
291 │ │ │ │ factor │
292 │ │ │ │ which should be │
293 │ │ │ │ multiplied by a │
294 │ │ │ │ base UERE to get │
295 │ │ │ │ an error │
296 │ │ │ │ estimate. │
297 ├───────────┼─────────┼─────────┼──────────────────┤
298 │gdop │ No │ numeric │ Hyperspherical │
299 │ │ │ │ dilution of │
300 │ │ │ │ precision, a │
301 │ │ │ │ dimensionless │
302 │ │ │ │ factor │
303 │ │ │ │ which should be │
304 │ │ │ │ multiplied by a │
305 │ │ │ │ base UERE to get │
306 │ │ │ │ an error │
307 │ │ │ │ estimate. │
308 ├───────────┼─────────┼─────────┼──────────────────┤
309 │satellites │ Yes │ list │ List of │
310 │ │ │ │ satellite │
311 │ │ │ │ objects in │
312 │ │ │ │ skyview │
313 └───────────┴─────────┴─────────┴──────────────────┘
314 Many devices compute dilution of precision factors but do not
315 include them in their reports. Many that do report DOPs report only
316 HDOP, two-dimensional circular error. gpsd always passes through
317 whatever the device actually reports, then attempts to fill in
318 other DOPs by calculating the appropriate determinants in a
319 covariance matrix based on the satellite view. DOPs may be missing
320 if some of these determinants are singular. It can even happen that
321 the device reports an error estimate in meters when the
322 corresponding DOP is unavailable; some devices use more
323 sophisticated error modeling than the covariance calculation.
324 The satellite list objects have the following elements:
326 Table 3. Satellite object
328 ┌─────┬─────────┬─────────┬──────────────────┐
329 │Name │ Always? │ Type │ Description │
330 ├─────┼─────────┼─────────┼──────────────────┤
331 │PRN │ Yes │ numeric │ PRN ID of the │
332 │ │ │ │ satellite. 1-63 │
333 │ │ │ │ are GNSS │
334 │ │ │ │ satellites, │
335 │ │ │ │ 64-96 are │
336 │ │ │ │ GLONASS │
337 │ │ │ │ satellites, │
338 │ │ │ │ 100-164 are SBAS │
339 │ │ │ │ satellites │
340 ├─────┼─────────┼─────────┼──────────────────┤
341 │az │ Yes │ numeric │ Azimuth, degrees │
342 │ │ │ │ from true north. │
343 ├─────┼─────────┼─────────┼──────────────────┤
344 │el │ Yes │ numeric │ Elevation in │
345 │ │ │ │ degrees. │
346 ├─────┼─────────┼─────────┼──────────────────┤
347 │ss │ Yes │ numeric │ Signal strength │
348 │ │ │ │ in dB. │
349 ├─────┼─────────┼─────────┼──────────────────┤
350 │used │ Yes │ boolean │ Used in current │
351 │ │ │ │ solution? │
352 │ │ │ │ (SBAS/WAAS/EGNOS │
353 │ │ │ │ satellites │
354 │ │ │ │ may be │
355 │ │ │ │ flagged used if │
356 │ │ │ │ the solution has │
357 │ │ │ │ corrections from │
358 │ │ │ │ them, but │
359 │ │ │ │ not all drivers │
360 │ │ │ │ make this │
361 │ │ │ │ information │
362 │ │ │ │ available.) │
363 └─────┴─────────┴─────────┴──────────────────┘
364 Note that satellite objects do not have a "class" field, as they
365 are never shipped outside of a SKY object.
366 When the C client library parses a SKY response, it will assert the
368 SATELLITE_SET bit in the top-level set member.
369 Here's an example:
371 {"class":"SKY","device":"/dev/pts/1",
373 "time":"2005-07-08T11:28:07.114Z",
374 "xdop":1.55,"hdop":1.24,"pdop":1.99,
375 "satellites":[
376 {"PRN":23,"el":6,"az":84,"ss":0,"used":false},
377 {"PRN":28,"el":7,"az":160,"ss":0,"used":false},
378 {"PRN":8,"el":66,"az":189,"ss":44,"used":true},
379 {"PRN":29,"el":13,"az":273,"ss":0,"used":false},
380 {"PRN":10,"el":51,"az":304,"ss":29,"used":true},
381 {"PRN":4,"el":15,"az":199,"ss":36,"used":true},
382 {"PRN":2,"el":34,"az":241,"ss":43,"used":true},
383 {"PRN":27,"el":71,"az":76,"ss":43,"used":true}]}
384 GST
386 A GST object is a pseudorange noise report.
387 Table 4. GST object
389 ┌───────┬─────────┬─────────┬──────────────────┐
390 │Name │ Always? │ Type │ Description │
391 ├───────┼─────────┼─────────┼──────────────────┤
392 │class │ Yes │ string │ Fixed: "GST" │
393 ├───────┼─────────┼─────────┼──────────────────┤
394 │device │ No │ string │ Name of │
395 │ │ │ │ originating │
396 │ │ │ │ device │
397 ├───────┼─────────┼─────────┼──────────────────┤
398 │time │ No │ numeric │ Seconds since │
399 │ │ │ │ the Unix epoch, │
400 │ │ │ │ UTC. May have a │
401 │ │ │ │ fractional part │
402 │ │ │ │ of up to .001sec │
403 │ │ │ │ precision. │
404 ├───────┼─────────┼─────────┼──────────────────┤
405 │rms │ No │ numeric │ Value of the │
406 │ │ │ │ standard │
407 │ │ │ │ deviation of the │
408 │ │ │ │ range inputs to │
409 │ │ │ │ the navigation │
410 │ │ │ │ process (range │
411 │ │ │ │ inputs include │
412 │ │ │ │ pseudoranges and │
413 │ │ │ │ DGPS │
414 │ │ │ │ corrections). │
415 ├───────┼─────────┼─────────┼──────────────────┤
416 │major │ No │ numeric │ Standard │
417 │ │ │ │ deviation of │
418 │ │ │ │ semi-major axis │
419 │ │ │ │ of error │
420 │ │ │ │ ellipse, in │
421 │ │ │ │ meters. │
422 ├───────┼─────────┼─────────┼──────────────────┤
423 │minor │ No │ numeric │ Standard │
424 │ │ │ │ deviation of │
425 │ │ │ │ semi-minor axis │
426 │ │ │ │ of error │
427 │ │ │ │ ellipse, in │
428 │ │ │ │ meters. │
429 ├───────┼─────────┼─────────┼──────────────────┤
430 │orient │ No │ numeric │ Orientation of │
431 │ │ │ │ semi-major axis │
432 │ │ │ │ of error │
433 │ │ │ │ ellipse, in │
434 │ │ │ │ degrees from │
435 │ │ │ │ true north. │
436 ├───────┼─────────┼─────────┼──────────────────┤
437 │lat │ No │ numeric │ Standard │
438 │ │ │ │ deviation of │
439 │ │ │ │ latitude error, │
440 │ │ │ │ in meters. │
441 ├───────┼─────────┼─────────┼──────────────────┤
442 │lon │ No │ numeric │ Standard │
443 │ │ │ │ deviation of │
444 │ │ │ │ longitude error, │
445 │ │ │ │ in meters. │
446 ├───────┼─────────┼─────────┼──────────────────┤
447 │alt │ No │ numeric │ Standard │
448 │ │ │ │ deviation of │
449 │ │ │ │ altitude error, │
450 │ │ │ │ in meters. │
451 └───────┴─────────┴─────────┴──────────────────┘
452 Here's an example:
453 {"class":"GST","device":"/dev/ttyUSB0",
455 "time":"2010-12-07T10:23:07.096Z","rms":2.440,
456 "major":1.660,"minor":1.120,"orient":68.989,
457 "lat":1.600,"lon":1.200,"alt":2.520}
458 ATT
460 An ATT object is a vehicle-attitude report. It is returned by
461 digital-compass and gyroscope sensors; depending on device, it may
462 include: heading, pitch, roll, yaw, gyroscope, and magnetic-field
463 readings. Because such sensors are often bundled as part of
464 marine-navigation systems, the ATT response may also include water
465 depth.
466 The "class" and "mode" fields will reliably be present. Others may
468 be reported or not depending on the specific device type.
469 Table 5. ATT object
471 ┌─────────┬─────────┬─────────┬──────────────────┐
472 │Name │ Always? │ Type │ Description │
473 ├─────────┼─────────┼─────────┼──────────────────┤
474 │class │ Yes │ string │ Fixed: "ATT" │
475 ├─────────┼─────────┼─────────┼──────────────────┤
476 │device │ Yes │ string │ Name of │
477 │ │ │ │ originating │
478 │ │ │ │ device │
479 ├─────────┼─────────┼─────────┼──────────────────┤
480 │time │ No │ numeric │ Seconds since │
481 │ │ │ │ the Unix epoch, │
482 │ │ │ │ UTC. May have a │
483 │ │ │ │ fractional │
484 │ │ │ │ part of up to │
485 │ │ │ │ .001sec │
486 │ │ │ │ precision. │
487 ├─────────┼─────────┼─────────┼──────────────────┤
488 │heading │ No │ numeric │ Heading, degrees │
489 │ │ │ │ from true north. │
490 ├─────────┼─────────┼─────────┼──────────────────┤
491 │mag_st │ No │ string │ Magnetometer │
492 │ │ │ │ status. │
493 ├─────────┼─────────┼─────────┼──────────────────┤
494 │pitch │ No │ numeric │ Pitch in │
495 │ │ │ │ degrees. │
496 ├─────────┼─────────┼─────────┼──────────────────┤
497 │pitch_st │ No │ string │ Pitch sensor │
498 │ │ │ │ status. │
499 ├─────────┼─────────┼─────────┼──────────────────┤
500 │yaw │ No │ numeric │ Yaw in degrees │
501 ├─────────┼─────────┼─────────┼──────────────────┤
502 │yaw_st │ No │ string │ Yaw sensor │
503 │ │ │ │ status. │
504 ├─────────┼─────────┼─────────┼──────────────────┤
505 │roll │ No │ numeric │ Roll in degrees. │
506 ├─────────┼─────────┼─────────┼──────────────────┤
507 │roll_st │ No │ string │ Roll sensor │
508 │ │ │ │ status. │
509 ├─────────┼─────────┼─────────┼──────────────────┤
510 │dip │ No │ numeric │ Local magnetic │
511 │ │ │ │ inclination, │
512 │ │ │ │ degrees, │
513 │ │ │ │ positive when │
514 │ │ │ │ the magnetic │
515 │ │ │ │ field points │
516 │ │ │ │ downward (into │
517 │ │ │ │ the Earth). │
518 ├─────────┼─────────┼─────────┼──────────────────┤
519 │mag_len │ No │ numeric │ Scalar magnetic │
520 │ │ │ │ field strength. │
521 ├─────────┼─────────┼─────────┼──────────────────┤
522 │mag_x │ No │ numeric │ X component of │
523 │ │ │ │ magnetic field │
524 │ │ │ │ strength. │
525 ├─────────┼─────────┼─────────┼──────────────────┤
526 │mag_y │ No │ numeric │ Y component of │
527 │ │ │ │ magnetic field │
528 │ │ │ │ strength. │
529 ├─────────┼─────────┼─────────┼──────────────────┤
530 │mag_z │ No │ numeric │ Z component of │
531 │ │ │ │ magnetic field │
532 │ │ │ │ strength. │
533 ├─────────┼─────────┼─────────┼──────────────────┤
534 │acc_len │ No │ numeric │ Scalar │
535 │ │ │ │ acceleration. │
536 ├─────────┼─────────┼─────────┼──────────────────┤
537 │acc_x │ No │ numeric │ X component of │
538 │ │ │ │ acceleration. │
539 ├─────────┼─────────┼─────────┼──────────────────┤
540 │acc_y │ No │ numeric │ Y component of │
541 │ │ │ │ acceleration. │
542 ├─────────┼─────────┼─────────┼──────────────────┤
543 │acc_z │ No │ numeric │ Z component of │
544 │ │ │ │ acceleration. │
545 ├─────────┼─────────┼─────────┼──────────────────┤
546 │gyro_x │ No │ numeric │ X component of │
547 │ │ │ │ acceleration. │
548 ├─────────┼─────────┼─────────┼──────────────────┤
549 │gyro_y │ No │ numeric │ Y component of │
550 │ │ │ │ acceleration. │
551 ├─────────┼─────────┼─────────┼──────────────────┤
552 │depth │ No │ numeric │ Water depth in │
553 │ │ │ │ meters. │
554 ├─────────┼─────────┼─────────┼──────────────────┤
555 │temp │ No │ numeric │ Temperature at │
556 │ │ │ │ sensor, degrees │
557 │ │ │ │ centigrade. │
558 └─────────┴─────────┴─────────┴──────────────────┘
559 The heading, pitch, and roll status codes (if present) vary by
560 device. For the TNT Revolution digital compasses, they are coded as
561 follows:
562 Table 6. Device flags
564 ┌─────┬────────────────────────────┐
565 │Code │ Description │
566 ├─────┼────────────────────────────┤
567 │C │ magnetometer calibration │
568 │ │ alarm │
569 ├─────┼────────────────────────────┤
570 │L │ low alarm │
571 ├─────┼────────────────────────────┤
572 │M │ low warning │
573 ├─────┼────────────────────────────┤
574 │N │ normal │
575 ├─────┼────────────────────────────┤
576 │O │ high warning │
577 ├─────┼────────────────────────────┤
578 │P │ high alarm │
579 ├─────┼────────────────────────────┤
580 │V │ magnetometer voltage level │
581 │ │ alarm │
582 └─────┴────────────────────────────┘
583 When the C client library parses a response of this kind, it will
584 assert ATT_IS.
585 Here's an example:
587 {"class":"ATT","time":1270938096.843,
589 "heading":14223.00,"mag_st":"N",
590 "pitch":169.00,"pitch_st":"N", "roll":-43.00,"roll_st":"N",
591 "dip":13641.000,"mag_x":2454.000}
592 And here are the commands:
594 ?VERSION;
596 Returns an object with the following attributes:
597 Table 7. VERSION object
599 ┌────────────┬─────────┬─────────┬──────────────────┐
600 │Name │ Always? │ Type │ Description │
601 ├────────────┼─────────┼─────────┼──────────────────┤
602 │class │ Yes │ string │ Fixed: "VERSION" │
603 ├────────────┼─────────┼─────────┼──────────────────┤
604 │release │ Yes │ string │ Public release │
605 │ │ │ │ level │
606 ├────────────┼─────────┼─────────┼──────────────────┤
607 │rev │ Yes │ string │ Internal │
608 │ │ │ │ revision-control │
609 │ │ │ │ level. │
610 ├────────────┼─────────┼─────────┼──────────────────┤
611 │proto_major │ Yes │ numeric │ API major │
612 │ │ │ │ revision level. │
613 ├────────────┼─────────┼─────────┼──────────────────┤
614 │proto_minor │ Yes │ numeric │ API minor │
615 │ │ │ │ revision level. │
616 ├────────────┼─────────┼─────────┼──────────────────┤
617 │remote │ No │ string │ URL of the │
618 │ │ │ │ remote daemon │
619 │ │ │ │ reporting this │
620 │ │ │ │ version. If │
621 │ │ │ │ empty, │
622 │ │ │ │ this is the │
623 │ │ │ │ version of the │
624 │ │ │ │ local daemon. │
625 └────────────┴─────────┴─────────┴──────────────────┘
626 The daemon ships a VERSION response to each client when the client
627 first connects to it.
628 When the C client library parses a response of this kind, it will
630 assert the VERSION_SET bit in the top-level set member.
631 Here's an example:
633 {"class":"VERSION","version":"2.40dev",
635 "rev":"06f62e14eae9886cde907dae61c124c53eb1101f",
636 "proto_major":3,"proto_minor":1
637 }
638 ?DEVICES;
640 Returns a device list object with the following elements:
641 Table 8. DEVICES object
643 ┌────────┬─────────┬────────┬──────────────────┐
644 │Name │ Always? │ Type │ Description │
645 ├────────┼─────────┼────────┼──────────────────┤
646 │class │ Yes │ string │ Fixed: "DEVICES" │
647 ├────────┼─────────┼────────┼──────────────────┤
648 │devices │ Yes │ list │ List of device │
649 │ │ │ │ descriptions │
650 ├────────┼─────────┼────────┼──────────────────┤
651 │remote │ No │ string │ URL of the │
652 │ │ │ │ remote daemon │
653 │ │ │ │ reporting the │
654 │ │ │ │ device set. If │
655 │ │ │ │ empty, │
656 │ │ │ │ this is a │
657 │ │ │ │ DEVICES response │
658 │ │ │ │ from the local │
659 │ │ │ │ daemon. │
660 └────────┴─────────┴────────┴──────────────────┘
661 When the C client library parses a response of this kind, it will
662 assert the DEVICELIST_SET bit in the top-level set member.
663 Here's an example:
665 {"class"="DEVICES","devices":[
667 {"class":"DEVICE","path":"/dev/pts/1","flags":1,"driver":"SiRF binary"},
668 {"class":"DEVICE","path":"/dev/pts/3","flags":4,"driver":"AIVDM"}]}
669 The daemon occasionally ships a bare DEVICE object to the client
671 (that is, one not inside a DEVICES wrapper). The data content of
672 these objects will be described later as a response to the ?DEVICE
673 command.
674 ?WATCH;
676 This command sets watcher mode. It also sets or elicits a report of
677 per-subscriber policy and the raw bit. An argument WATCH object
678 changes the subscriber's policy. The response describes the
679 subscriber's policy. The response will also include a DEVICES
680 object.
681 A WATCH object has the following elements:
683 Table 9. WATCH object
685 ┌────────┬─────────┬─────────┬──────────────────┐
686 │Name │ Always? │ Type │ Description │
687 ├────────┼─────────┼─────────┼──────────────────┤
688 │class │ Yes │ string │ Fixed: "WATCH" │
689 ├────────┼─────────┼─────────┼──────────────────┤
690 │enable │ No │ boolean │ Enable (true) or │
691 │ │ │ │ disable (false) │
692 │ │ │ │ watcher mode. │
693 │ │ │ │ Default is │
694 │ │ │ │ true. │
695 ├────────┼─────────┼─────────┼──────────────────┤
696 │json │ No │ boolean │ Enable (true) or │
697 │ │ │ │ disable (false) │
698 │ │ │ │ dumping of JSON │
699 │ │ │ │ reports. │
700 │ │ │ │ Default is │
701 │ │ │ │ false. │
702 ├────────┼─────────┼─────────┼──────────────────┤
703 │nmea │ No │ boolean │ Enable (true) or │
704 │ │ │ │ disable (false) │
705 │ │ │ │ dumping of │
706 │ │ │ │ binary │
707 │ │ │ │ packets as │
708 │ │ │ │ pseudo-NMEA. │
709 │ │ │ │ Default is │
710 │ │ │ │ false. │
711 ├────────┼─────────┼─────────┼──────────────────┤
712 │raw │ No │ integer │ Controls 'raw' │
713 │ │ │ │ mode. When this │
714 │ │ │ │ attribute is set │
715 │ │ │ │ to 1 for a │
716 │ │ │ │ channel, gpsd │
717 │ │ │ │ reports the │
718 │ │ │ │ unprocessed │
719 │ │ │ │ NMEA or AIVDM │
720 │ │ │ │ data stream from │
721 │ │ │ │ whatever device │
722 │ │ │ │ is attached. │
723 │ │ │ │ Binary GPS │
724 │ │ │ │ packets are │
725 │ │ │ │ hex-dumped. │
726 │ │ │ │ RTCM2 and RTCM3 │
727 │ │ │ │ packets │
728 │ │ │ │ are not dumped │
729 │ │ │ │ in raw mode. │
730 │ │ │ │ When this │
731 │ │ │ │ attribute is set │
732 │ │ │ │ to 2 for a │
733 │ │ │ │ channel that │
734 │ │ │ │ processes binary │
735 │ │ │ │ data, gpsd │
736 │ │ │ │ reports the │
737 │ │ │ │ received data │
738 │ │ │ │ verbatim │
739 │ │ │ │ without │
740 │ │ │ │ hex-dumping. │
741 ├────────┼─────────┼─────────┼──────────────────┤
742 │scaled │ No │ boolean │ If true, apply │
743 │ │ │ │ scaling divisors │
744 │ │ │ │ to output before │
745 │ │ │ │ dumping; │
746 │ │ │ │ default is │
747 │ │ │ │ false. │
748 ├────────┼─────────┼─────────┼──────────────────┤
749 │split24 │ No │ boolean │ If true, │
750 │ │ │ │ aggregate AIS │
751 │ │ │ │ type24 sentence │
752 │ │ │ │ parts. If │
753 │ │ │ │ false, │
754 │ │ │ │ report │
755 │ │ │ │ each part as a │
756 │ │ │ │ separate JSON │
757 │ │ │ │ object, leaving │
758 │ │ │ │ the │
759 │ │ │ │ client │
760 │ │ │ │ to match MMSIs │
761 │ │ │ │ and aggregate. │
762 │ │ │ │ Default is │
763 │ │ │ │ false. │
764 │ │ │ │ Applies only to │
765 │ │ │ │ AIS reports. │
766 ├────────┼─────────┼─────────┼──────────────────┤
767 │pps │ No │ boolean │ If true, emit │
768 │ │ │ │ the TOFF JSON │
769 │ │ │ │ message on each │
770 │ │ │ │ cycle and a │
771 │ │ │ │ PPS JSON │
772 │ │ │ │ message when the │
773 │ │ │ │ device issues │
774 │ │ │ │ 1PPS. Default is │
775 │ │ │ │ false. │
776 ├────────┼─────────┼─────────┼──────────────────┤
777 │device │ No │ string │ If present, │
778 │ │ │ │ enable watching │
779 │ │ │ │ only of the │
780 │ │ │ │ specified device │
781 │ │ │ │ rather than │
782 │ │ │ │ all devices. │
783 │ │ │ │ Useful with raw │
784 │ │ │ │ and NMEA modes │
785 │ │ │ │ in which │
786 │ │ │ │ device responses │
787 │ │ │ │ aren't tagged. │
788 │ │ │ │ Has no effect │
789 │ │ │ │ when used │
790 │ │ │ │ with │
791 │ │ │ │ enable:false. │
792 ├────────┼─────────┼─────────┼──────────────────┤
793 │remote │ No │ string │ URL of the │
794 │ │ │ │ remote daemon │
795 │ │ │ │ reporting the │
796 │ │ │ │ watch set. If │
797 │ │ │ │ empty, │
798 │ │ │ │ this is a WATCH │
799 │ │ │ │ response from │
800 │ │ │ │ the local │
801 │ │ │ │ daemon. │
802 └────────┴─────────┴─────────┴──────────────────┘
803 There is an additional boolean "timing" attribute which is
804 undocumented because that portion of the interface is considered
805 unstable and for developer use only.
806 In watcher mode, GPS reports are dumped as TPV and SKY responses.
808 AIS, Subframe and RTCM reporting is described in the next section.
809 When the C client library parses a response of this kind, it will
811 assert the POLICY_SET bit in the top-level set member.
812 Here's an example:
814 {"class":"WATCH", "raw":1,"scaled":true}
816 ?POLL;
818 The POLL command requests data from the last-seen fixes on all
819 active GPS devices. Devices must previously have been activated by
820 ?WATCH to be pollable.
821 Polling can lead to possibly surprising results when it is used on
823 a device such as an NMEA GPS for which a complete fix has to be
824 accumulated from several sentences. If you poll while those
825 sentences are being emitted, the response will contain the last
826 complete fix data and may be as much as one cycle time (typically 1
827 second) stale.
828 The POLL response will contain a timestamped list of TPV objects
830 describing cached data, and a timestamped list of SKY objects
831 describing satellite configuration. If a device has not seen fixes,
832 it will be reported with a mode field of zero.
833 Table 10. POLL object
835 ┌───────┬─────────┬────────────┬──────────────────┐
836 │Name │ Always? │ Type │ Description │
837 ├───────┼─────────┼────────────┼──────────────────┤
838 │class │ Yes │ string │ Fixed: "POLL" │
839 ├───────┼─────────┼────────────┼──────────────────┤
840 │time │ Yes │ Numeric │ Timestamp in ISO │
841 │ │ │ │ 8601 format. May │
842 │ │ │ │ have a │
843 │ │ │ │ fractional │
844 │ │ │ │ part of up to │
845 │ │ │ │ .001sec │
846 │ │ │ │ precision. │
847 ├───────┼─────────┼────────────┼──────────────────┤
848 │active │ Yes │ Numeric │ Count of active │
849 │ │ │ │ devices. │
850 ├───────┼─────────┼────────────┼──────────────────┤
851 │tpv │ Yes │ JSON array │ Comma-separated │
852 │ │ │ │ list of TPV │
853 │ │ │ │ objects. │
854 ├───────┼─────────┼────────────┼──────────────────┤
855 │sky │ Yes │ JSON array │ Comma-separated │
856 │ │ │ │ list of SKY │
857 │ │ │ │ objects. │
858 └───────┴─────────┴────────────┴──────────────────┘
859 Here's an example of a POLL response:
860 {"class":"POLL","time":"2010-06-04T10:31:00.289Z","active":1,
862 "tpv":[{"class":"TPV","device":"/dev/ttyUSB0",
863 "time":"2010-09-08T13:33:06.095Z",
864 "ept":0.005,"lat":40.035093060,
865 "lon":-75.519748733,"track":99.4319,"speed":0.123,"mode":2}],
866 "sky":[{"class":"SKY","device":"/dev/ttyUSB0",
867 "time":1270517264.240,"hdop":9.20,
868 "satellites":[{"PRN":16,"el":55,"az":42,"ss":36,"used":true},
869 {"PRN":19,"el":25,"az":177,"ss":0,"used":false},
870 {"PRN":7,"el":13,"az":295,"ss":0,"used":false},
871 {"PRN":6,"el":56,"az":135,"ss":32,"used":true},
872 {"PRN":13,"el":47,"az":304,"ss":0,"used":false},
873 {"PRN":23,"el":66,"az":259,"ss":0,"used":false},
874 {"PRN":20,"el":7,"az":226,"ss":0,"used":false},
875 {"PRN":3,"el":52,"az":163,"ss":32,"used":true},
876 {"PRN":31,"el":16,"az":102,"ss":0,"used":false}
877 ]}]}
878 Note
880 Client software should not assume the field inventory of the
881 POLL response is fixed for all time. As gpsd collects and
882 caches more data from more sensor types, those data are likely
883 to find their way into this response.
884 TOFF
886 This message is emitted on each cycle and reports the offset
887 between the host's clock time and the GPS time at top of second
888 (actually, when the first data for the reporting cycle is
889 received).
890 This message exactly mirrors the PPS message except for two
892 details.
893 TOFF emits no NTP precision, this is assumed to be -2. See the NTP
895 documentation for their definition of precision.
896 The TOFF message reports the GPS time as derived from the GPS
898 serial data stream. The PPS message reports the GPS time as derived
899 from the GPS PPS pulse.
900 A TOFF object has the following elements:
902 Table 11. TOFF object
904 ┌───────────┬─────────┬─────────┬──────────────────┐
905 │Name │ Always? │ Type │ Description │
906 ├───────────┼─────────┼─────────┼──────────────────┤
907 │class │ Yes │ string │ Fixed: "TOFF" │
908 ├───────────┼─────────┼─────────┼──────────────────┤
909 │device │ Yes │ string │ Name of │
910 │ │ │ │ originating │
911 │ │ │ │ device │
912 ├───────────┼─────────┼─────────┼──────────────────┤
913 │real_sec │ Yes │ numeric │ seconds from the │
914 │ │ │ │ GPS clock │
915 ├───────────┼─────────┼─────────┼──────────────────┤
916 │real_nsec │ Yes │ numeric │ nanoseconds from │
917 │ │ │ │ the GPS clock │
918 ├───────────┼─────────┼─────────┼──────────────────┤
919 │clock_sec │ Yes │ numeric │ seconds from the │
920 │ │ │ │ system clock │
921 ├───────────┼─────────┼─────────┼──────────────────┤
922 │clock_nsec │ Yes │ numeric │ nanoseconds from │
923 │ │ │ │ the system clock │
924 └───────────┴─────────┴─────────┴──────────────────┘
925 This message is emitted once per second to watchers of a device and
926 is intended to report the time stamps of the in-band report of the
927 GPS and seconds as reported by the system clock (which may be
928 NTP-corrected) when the first valid timestamp of the reporting
929 cycle was seen.
930 The message contains two second/nanosecond pairs: real_sec and
932 real_nsec contain the time the GPS thinks it was at the start of
933 the current cycle; clock_sec and clock_nsec contain the time the
934 system clock thinks it was on receipt of the first timing message
935 of the cycle. real_nsec is always to nanosecond precision.
936 clock_nsec is nanosecond precision on most systems.
937 Here's an example:
939 {"class":"TOFF","device":"/dev/ttyUSB0",
941 "real_sec":1330212592, "real_nsec":343182,
942 "clock_sec":1330212592,"clock_nsec":343184,
943 "precision":-2}}
944 PPS
946 This message is emitted each time the daemon sees a valid PPS
947 (Pulse Per Second) strobe from a device.
948 This message exactly mirrors the TOFF message except for two
950 details.
951 PPS emits the NTP precision. See the NTP documentation for their
953 definition of precision.
954 The TOFF message reports the GPS time as derived from the GPS
956 serial data stream. The PPS message reports the GPS time as derived
957 from the GPS PPS pulse.
958 There are various sources of error in the reported clock times. The
960 speed of the serial connection between the GPS and the system adds
961 a delay to start of cycle detection. An even bigger error is added
962 by the variable computation time inside the GPS. Taken together the
963 time derived from the start of the GPS cycle can have offsets of 10
964 millisecond to 700 milliseconds and combined jjitter and wander of
965 100 to 300 millisecond.
966 A PPS object has the following elements:
968 Table 12. PPS object
970 ┌───────────┬─────────┬─────────┬──────────────────┐
971 │Name │ Always? │ Type │ Description │
972 ├───────────┼─────────┼─────────┼──────────────────┤
973 │class │ Yes │ string │ Fixed: "PPS" │
974 ├───────────┼─────────┼─────────┼──────────────────┤
975 │device │ Yes │ string │ Name of │
976 │ │ │ │ originating │
977 │ │ │ │ device │
978 ├───────────┼─────────┼─────────┼──────────────────┤
979 │real_sec │ Yes │ numeric │ seconds from the │
980 │ │ │ │ PPS source │
981 ├───────────┼─────────┼─────────┼──────────────────┤
982 │real_nsec │ Yes │ numeric │ nanoseconds from │
983 │ │ │ │ the PPS source │
984 ├───────────┼─────────┼─────────┼──────────────────┤
985 │clock_sec │ Yes │ numeric │ seconds from the │
986 │ │ │ │ system clock │
987 ├───────────┼─────────┼─────────┼──────────────────┤
988 │clock_nsec │ Yes │ numeric │ nanoseconds from │
989 │ │ │ │ the system clock │
990 ├───────────┼─────────┼─────────┼──────────────────┤
991 │precision │ Yes │ numeric │ NTP style │
992 │ │ │ │ estimate of PPS │
993 │ │ │ │ precision │
994 └───────────┴─────────┴─────────┴──────────────────┘
995 This message is emitted once per second to watchers of a device
996 emitting PPS, and reports the time of the start of the GPS second
997 (when the 1PPS arrives) and seconds as reported by the system clock
998 (which may be NTP-corrected) at that moment.
999 The message contains two second/nanosecond pairs: real_sec and
1001 real_nsec contain the time the GPS thinks it was at the PPS edge;
1002 clock_sec and clock_nsec contain the time the system clock thinks
1003 it was at the PPS edge. real_nsec is always to nanosecond
1004 precision. clock_nsec is nanosecond precision on most systems.
1005 There are various sources of error in the reported clock times. For
1007 PPS delivered via a real serial-line strobe, serial-interrupt
1008 latency plus processing time to the timer call should be bounded
1009 above by about 10 microseconds; that can be reduced to less than 1
1010 microsecond if your kernel supports RFC 2783. USB1.1-to-serial
1011 control-line emulation is limited to about 1 millisecond. seconds.
1012 Here's an example:
1014 {"class":"PPS","device":"/dev/ttyUSB0",
1016 "real_sec":1330212592, "real_nsec":343182,
1017 "clock_sec":1330212592,"clock_nsec":343184,
1018 "precision":-3}
1019 OSC
1021 This message reports the status of a GPS-disciplined oscillator
1022 (GPSDO). The GPS PPS output (which has excellent long-term
1023 stability) is typically used to discipline a local oscillator with
1024 much better short-term stability (such as a rubidium atomic clock).
1025 An OSC object has the following elements:
1027 Table 13. OSC object
1029 ┌────────────┬─────────┬─────────┬──────────────────┐
1030 │Name │ Always? │ Type │ Description │
1031 ├────────────┼─────────┼─────────┼──────────────────┤
1032 │class │ Yes │ string │ Fixed: "OSC" │
1033 ├────────────┼─────────┼─────────┼──────────────────┤
1034 │device │ Yes │ string │ Name of │
1035 │ │ │ │ originating │
1036 │ │ │ │ device. │
1037 ├────────────┼─────────┼─────────┼──────────────────┤
1038 │running │ Yes │ boolean │ If true, the │
1039 │ │ │ │ oscillator is │
1040 │ │ │ │ currently │
1041 │ │ │ │ running. │
1042 │ │ │ │ Oscillators may │
1043 │ │ │ │ require warm-up │
1044 │ │ │ │ time at start of │
1045 │ │ │ │ day. │
1046 ├────────────┼─────────┼─────────┼──────────────────┤
1047 │reference │ Yes │ boolean │ If true, the │
1048 │ │ │ │ oscillator is │
1049 │ │ │ │ receiving a GPS │
1050 │ │ │ │ PPS signal. │
1051 ├────────────┼─────────┼─────────┼──────────────────┤
1052 │disciplined │ Yes │ boolean │ If true, the GPS │
1053 │ │ │ │ PPS signal is │
1054 │ │ │ │ sufficiently │
1055 │ │ │ │ stable and is │
1056 │ │ │ │ being used to │
1057 │ │ │ │ discipline the │
1058 │ │ │ │ local │
1059 │ │ │ │ oscillator. │
1060 ├────────────┼─────────┼─────────┼──────────────────┤
1061 │delta │ Yes │ numeric │ The time │
1062 │ │ │ │ difference (in │
1063 │ │ │ │ nanoseconds) │
1064 │ │ │ │ between the │
1065 │ │ │ │ GPS-disciplined │
1066 │ │ │ │ oscillator PPS │
1067 │ │ │ │ output pulse and │
1068 │ │ │ │ the most recent │
1069 │ │ │ │ GPS PPS input │
1070 │ │ │ │ pulse. │
1071 └────────────┴─────────┴─────────┴──────────────────┘
1072 Here's an example:
1073 {"class":"OSC","running":true,"device":"/dev/ttyUSB0",
1075 "reference":true,"disciplined":true,"delta":67}
1076 ?DEVICE
1078 This command reports (when followed by ';') the state of a device,
1079 or sets (when followed by '=' and a DEVICE object) device-specific
1080 control bits, notably the device's speed and serial mode and the
1081 native-mode bit. The parameter-setting form will be rejected if
1082 more than one client is attached to the channel.
1083 Pay attention to the response, because it is possible for this
1085 command to fail if the GPS does not support a speed-switching
1086 command or only supports some combinations of serial modes. In case
1087 of failure, the daemon and GPS will continue to communicate at the
1088 old speed.
1089 Use the parameter-setting form with caution. On USB and Bluetooth
1091 GPSes it is also possible for serial mode setting to fail either
1092 because the serial adaptor chip does not support non-8N1 modes or
1093 because the device firmware does not properly synchronize the
1094 serial adaptor chip with the UART on the GPS chipset when the speed
1095 changes. These failures can hang your device, possibly requiring a
1096 GPS power cycle or (in extreme cases) physically disconnecting the
1097 NVRAM backup battery.
1098 A DEVICE object has the following elements:
1100 Table 14. DEVICE object
1102 ┌──────────┬──────────────────┬─────────┬────────────────────┐
1103 │Name │ Always? │ Type │ Description │
1104 ├──────────┼──────────────────┼─────────┼────────────────────┤
1105 │class │ Yes │ string │ Fixed: "DEVICE" │
1106 ├──────────┼──────────────────┼─────────┼────────────────────┤
1107 │path │ No │ string │ Name the device │
1108 │ │ │ │ for which the │
1109 │ │ │ │ control bits are │
1110 │ │ │ │ being │
1111 │ │ │ │ reported, or for │
1112 │ │ │ │ which they are │
1113 │ │ │ │ to be applied. │
1114 │ │ │ │ This │
1115 │ │ │ │ attribute │
1116 │ │ │ │ may be omitted │
1117 │ │ │ │ only when there │
1118 │ │ │ │ is exactly one │
1119 │ │ │ │ subscribed │
1120 │ │ │ │ channel. │
1121 ├──────────┼──────────────────┼─────────┼────────────────────┤
1122 │activated │ No │ string │ Time the device │
1123 │ │ │ │ was activated as │
1124 │ │ │ │ an ISO8601 │
1125 │ │ │ │ timestamp. │
1126 │ │ │ │ If the device is │
1127 │ │ │ │ inactive this │
1128 │ │ │ │ attribute is │
1129 │ │ │ │ absent. │
1130 ├──────────┼──────────────────┼─────────┼────────────────────┤
1131 │flags │ No │ integer │ Bit vector of │
1132 │ │ │ │ property flags. │
1133 │ │ │ │ Currently defined │
1134 │ │ │ │ flags are: │
1135 │ │ │ │ describe │
1136 │ │ │ │ packet types seen │
1137 │ │ │ │ so far (GPS, │
1138 │ │ │ │ RTCM2, RTCM3, │
1139 │ │ │ │ AIS). Won't │
1140 │ │ │ │ be reported if │
1141 │ │ │ │ empty, e.g. before │
1142 │ │ │ │ gpsd has seen │
1143 │ │ │ │ identifiable │
1144 │ │ │ │ packets from │
1145 │ │ │ │ the device. │
1146 ├──────────┼──────────────────┼─────────┼────────────────────┤
1147 │driver │ No │ string │ GPSD's name for │
1148 │ │ │ │ the device driver │
1149 │ │ │ │ type. Won't be │
1150 │ │ │ │ reported before │
1151 │ │ │ │ gpsd has seen │
1152 │ │ │ │ identifiable │
1153 │ │ │ │ packets from │
1154 │ │ │ │ the device. │
1155 ├──────────┼──────────────────┼─────────┼────────────────────┤
1156 │subtype │ When the daemon │ string │ Whatever version │
1157 │ │ sees a delayed │ │ information the │
1158 │ │ response to a │ │ device returned. │
1159 │ │ probe for │ │ │
1160 │ │ subtype or │ │ │
1161 │ │ firmware-version │ │ │
1162 │ │ information. │ │ │
1163 ├──────────┼──────────────────┼─────────┼────────────────────┤
1164 │bps │ No │ integer │ Device speed in │
1165 │ │ │ │ bits per second. │
1166 ├──────────┼──────────────────┼─────────┼────────────────────┤
1167 │parity │ No │ string │ N, O or E for no │
1168 │ │ │ │ parity, odd, or │
1169 │ │ │ │ even. │
1170 ├──────────┼──────────────────┼─────────┼────────────────────┤
1171 │stopbits │ Yes │ string │ Stop bits (1 or │
1172 │ │ │ │ 2). │
1173 ├──────────┼──────────────────┼─────────┼────────────────────┤
1174 │native │ No │ integer │ 0 means NMEA mode │
1175 │ │ │ │ and 1 means │
1176 │ │ │ │ alternate │
1177 │ │ │ │ mode (binary if it │
1178 │ │ │ │ has one, for SiRF │
1179 │ │ │ │ and Evermore │
1180 │ │ │ │ chipsets in │
1181 │ │ │ │ particular). │
1182 │ │ │ │ Attempting to set │
1183 │ │ │ │ this mode on a │
1184 │ │ │ │ non-GPS │
1185 │ │ │ │ device will │
1186 │ │ │ │ yield an error. │
1187 ├──────────┼──────────────────┼─────────┼────────────────────┤
1188 │cycle │ No │ real │ Device cycle time │
1189 │ │ │ │ in seconds. │
1190 ├──────────┼──────────────────┼─────────┼────────────────────┤
1191 │mincycle │ No │ real │ Device minimum │
1192 │ │ │ │ cycle time in │
1193 │ │ │ │ seconds. Reported │
1194 │ │ │ │ from ?DEVICE │
1195 │ │ │ │ when (and only │
1196 │ │ │ │ when) the rate is │
1197 │ │ │ │ switchable. It is │
1198 │ │ │ │ read-only and │
1199 │ │ │ │ not settable. │
1200 └──────────┴──────────────────┴─────────┴────────────────────┘
1201 The serial parameters will (bps, parity, stopbits) be omitted in a
1202 response describing a TCP/IP source such as an Ntrip, DGPSIP, or
1203 AIS feed; on a serial device they will always be present.
1204 The contents of the flags field should be interpreted as follows:
1206 Table 15. Device flags
1208 ┌───────────┬───────┬─────────────────────┐
1209 │C #define │ Value │ Description │
1210 ├───────────┼───────┼─────────────────────┤
1211 │SEEN_GPS │ 0x01 │ GPS data has been │
1212 │ │ │ seen on this device │
1213 ├───────────┼───────┼─────────────────────┤
1214 │SEEN_RTCM2 │ 0x02 │ RTCM2 data has been │
1215 │ │ │ seen on this device │
1216 ├───────────┼───────┼─────────────────────┤
1217 │SEEN_RTCM3 │ 0x04 │ RTCM3 data has been │
1218 │ │ │ seen on this device │
1219 ├───────────┼───────┼─────────────────────┤
1220 │SEEN_AIS │ 0x08 │ AIS data has been │
1221 │ │ │ seen on this device │
1222 └───────────┴───────┴─────────────────────┘
1223 When the C client library parses a response of this kind, it will
1224 assert the DEVICE_SET bit in the top-level set member.
1225 Here's an example:
1227 {"class":"DEVICE","bps":4800,"parity":"N","stopbits":1,"native":0}
1229 When a client is in watcher mode, the daemon will ship it DEVICE
1231 notifications when a device is added to the pool or deactivated.
1232 When the C client library parses a response of this kind, it will
1234 assert the DEVICE_SET bit in the top-level set member.
1235 Here's an example:
1237 {"class":"DEVICE","path":"/dev/pts1","activated":0}
1239 The daemon may ship an error object in response to a syntactically
1241 invalid command line or unknown command. It has the following elements:
1242 Table 16. ERROR notification object
1244 ┌────────┬─────────┬────────┬────────────────┐
1245 │Name │ Always? │ Type │ Description │
1246 ├────────┼─────────┼────────┼────────────────┤
1247 │class │ Yes │ string │ Fixed: "ERROR" │
1248 ├────────┼─────────┼────────┼────────────────┤
1249 │message │ Yes │ string │ Textual error │
1250 │ │ │ │ message │
1251 └────────┴─────────┴────────┴────────────────┘
1252 Here's an example:
1254 {"class":"ERROR","message":"Unrecognized request '?FOO'"}
1256 When the C client library parses a response of this kind, it will
1258 assert the ERR_SET bit in the top-level set member.
1259
1261 RTCM-104 is a family of serial protocols used for broadcasting
1262 pseudorange corrections from differential-GPS reference stations. Many
1263 GPS receivers can accept these corrections to improve their reporting
1264 accuracy.
1265 RTCM-104 comes in two major and incompatible flavors, 2.x and 3.x. Each
1267 major flavor has minor (compatible) revisions.
1268 The applicable standard for RTCM Version 2.x is RTCM Recommended
1270 Standards for Differential NAVSTAR GPS Service RTCM Paper 194-93/SC
1271 104-STD. For RTCM 3.1 it is RTCM Paper 177-2006-SC104-STD. Ordering
1272 instructions for both standards are accessible from the website of the
1273 Radio Technical Commission for Maritime Services[1] under
1274 "Publications".
1275 RTCM WIRE TRANSMISSIONS
1277 Differential-GPS correction stations consist of a GPS reference
1278 receiver coupled to a low frequency (LF) transmitter. The GPS reference
1279 receiver is a survey-grade GPS that does GPS carrier tracking and can
1280 work out its own position to a few millimeters. It generates range and
1281 range-rate corrections and encodes them into RTCM104. It ships the
1282 RTCM104 to the LF transmitter over serial rs-232 signal at 100 baud or
1283 200 baud depending on the requirements of the transmitter.
1284 The LF transmitter broadcasts the approximately 300khz radio signal
1286 that differential-GPS radio receivers pick up. Transmitters that are
1287 meant to have a higher range will need to transmit at the slower rate.
1288 The higher the data rate the harder it will be for the remote radio
1289 receiver to receive with a good signal-to-noise ration. (Higher data
1290 rate signals can't be averaged over as long a time frame, hence they
1291 appear noisier.)
1292 RTCM WIRE FORMATS
1294 An RTCM 2.x message consists of a sequence of up to 33 30-bit words.
1295 The 24 most significant bits of each word are data and the six least
1296 significant bits are parity. The parity algorithm used is the same
1297 ISGPS-2000 as that used on GPS satellite downlinks. Each RTCM 2.x
1298 message consists of two header words followed by zero or more data
1299 words, depending upon message type.
1300 An RTCM 3.x message begins with a fixed leader byte 0xD3. That is
1302 followed by six bits of version information and 10 bits of payload
1303 length information. Following that is the payload; following the
1304 payload is a 3-byte checksum of the payload using the Qualcomm CRC-24Q
1305 algorithm.
1306 RTCM2 JSON FORMAT
1308 Each RTCM2 message is dumped as a single JSON object per message, with
1309 the message fields as attributes of that object. Arrays of satellite,
1310 station, and constellation statistics become arrays of JSON
1311 sub-objects. Each sentence will normally also have a "device" field
1312 containing the pathname of the originating device.
1313 All attributes other than the device field are mandatory. Header
1315 attributes are emitted before others.
1316 Header portion
1318 Table 17. SKY object
1319 ┌───────────────┬─────────┬─────────────────────────────┐
1320 │Name │ Type │ │
1321 │ │ │ Description │
1322 ├───────────────┼─────────┼─────────────────────────────┤
1323 │class │ string │ │
1324 │ │ │ Fixed: │
1325 │ │ │ "RTCM2". │
1326 ├───────────────┼─────────┼─────────────────────────────┤
1327 │type │ integer │ │
1328 │ │ │ Message │
1329 │ │ │ type (1-9). │
1330 ├───────────────┼─────────┼─────────────────────────────┤
1331 │station_id │ integer │ │
1332 │ │ │ The id of │
1333 │ │ │ the GPS │
1334 │ │ │ reference │
1335 │ │ │ receiver. │
1336 │ │ │ The LF │
1337 │ │ │ transmitters │
1338 │ │ │ also have │
1339 │ │ │ (different) │
1340 │ │ │ id numbers. │
1341 ├───────────────┼─────────┼─────────────────────────────┤
1342 │zcount │ real │ │
1343 │ │ │ The │
1344 │ │ │ reference │
1345 │ │ │ time of the │
1346 │ │ │ corrections │
1347 │ │ │ in the │
1348 │ │ │ message in │
1349 │ │ │ seconds │
1350 │ │ │ within the │
1351 │ │ │ current │
1352 │ │ │ hour. Note │
1353 │ │ │ that it is │
1354 │ │ │ in GPS time, │
1355 │ │ │ which is │
1356 │ │ │ some seconds │
1357 │ │ │ ahead of UTC │
1358 │ │ │ (see the │
1359 │ │ │ U.S. Naval │
1360 │ │ │ Observatory's │
1361 │ │ │ table of │
1362 │ │ │ leap second │
1363 │ │ │ corrections[2]). │
1364 ├───────────────┼─────────┼─────────────────────────────┤
1365 │seqnum │ integer │ │
1366 │ │ │ Sequence number. │
1367 │ │ │ Only 3 bits │
1368 │ │ │ wide, wraps │
1369 │ │ │ after 7. │
1370 ├───────────────┼─────────┼─────────────────────────────┤
1371 │length │ integer │ │
1372 │ │ │ The number of │
1373 │ │ │ words after the │
1374 │ │ │ header that │
1375 │ │ │ comprise the │
1376 │ │ │ message. │
1377 ├───────────────┼─────────┼─────────────────────────────┤
1378 │station_health │ integer │ │
1379 │ │ │ Station │
1380 │ │ │ transmission │
1381 │ │ │ status. │
1382 │ │ │ Indicates the │
1383 │ │ │ health of the │
1384 │ │ │ beacon as a │
1385 │ │ │ reference │
1386 │ │ │ source. Any │
1387 │ │ │ nonzero value │
1388 │ │ │ means the │
1389 │ │ │ satellite is │
1390 │ │ │ probably │
1391 │ │ │ transmitting bad │
1392 │ │ │ data and should │
1393 │ │ │ not be used in a │
1394 │ │ │ fix. 6 means the │
1395 │ │ │ transmission is │
1396 │ │ │ unmonitored. 7 │
1397 │ │ │ means the │
1398 │ │ │ station is not │
1399 │ │ │ working │
1400 │ │ │ properly. Other │
1401 │ │ │ values are │
1402 │ │ │ defined by the │
1403 │ │ │ beacon operator. │
1404 └───────────────┴─────────┴─────────────────────────────┘
1405 <message type> is one of
1407 1
1409 full corrections - one message containing corrections for all
1410 GPS satellites in view. This is not common.
1411 3
1413 reference station parameters - the position of the reference
1414 station GPS antenna.
1415 4
1417 datum — the datum to which the DGPS data is referred.
1418 5
1420 constellation health — information about the satellites the
1421 beacon can see.
1422 6
1424 null message — just a filler.
1425 7
1427 radio beacon almanac — information about this or other beacons.
1428 9
1430 subset corrections — a message containing corrections for only
1431 a subset of the GPS satellites in view.
1432 16
1434 special message — a text message from the beacon operator.
1435 31
1437 GLONASS subset corrections — a message containing corrections
1438 for a set of the GLONASS satellites in view.
1439 Type 1 and 9: Correction data
1441 One or more satellite objects follow the header for type 1 or type
1442 9 messages. Here is the format:
1443 Table 18. Satellite object
1445 ┌──────┬─────────┬─────────────────────────┐
1446 │Name │ Type │ │
1447 │ │ │ Description │
1448 ├──────┼─────────┼─────────────────────────┤
1449 │ident │ integer │ │
1450 │ │ │ The PRN │
1451 │ │ │ number of │
1452 │ │ │ the │
1453 │ │ │ satellite │
1454 │ │ │ for which │
1455 │ │ │ this is │
1456 │ │ │ correction │
1457 │ │ │ data. │
1458 ├──────┼─────────┼─────────────────────────┤
1459 │udre │ integer │ │
1460 │ │ │ User │
1461 │ │ │ Differential │
1462 │ │ │ Range Error │
1463 │ │ │ (0-3). See │
1464 │ │ │ the table │
1465 │ │ │ following │
1466 │ │ │ for values. │
1467 ├──────┼─────────┼─────────────────────────┤
1468 │iod │ integer │ │
1469 │ │ │ Issue Of │
1470 │ │ │ Data, │
1471 │ │ │ matching the │
1472 │ │ │ IOD for the │
1473 │ │ │ current │
1474 │ │ │ ephemeris of │
1475 │ │ │ this │
1476 │ │ │ satellite, │
1477 │ │ │ as │
1478 │ │ │ transmitted │
1479 │ │ │ by the │
1480 │ │ │ satellite. │
1481 │ │ │ The IOD is a │
1482 │ │ │ unique tag │
1483 │ │ │ that │
1484 │ │ │ identifies │
1485 │ │ │ the │
1486 │ │ │ ephemeris; │
1487 │ │ │ the GPS │
1488 │ │ │ using the │
1489 │ │ │ DGPS │
1490 │ │ │ correction │
1491 │ │ │ and the DGPS │
1492 │ │ │ generating │
1493 │ │ │ the data │
1494 │ │ │ must use the │
1495 │ │ │ same orbital │
1496 │ │ │ positions │
1497 │ │ │ for the │
1498 │ │ │ satellite. │
1499 ├──────┼─────────┼─────────────────────────┤
1500 │prc │ real │ │
1501 │ │ │ The │
1502 │ │ │ pseudorange │
1503 │ │ │ error in │
1504 │ │ │ meters for │
1505 │ │ │ this │
1506 │ │ │ satellite as │
1507 │ │ │ measured by │
1508 │ │ │ the beacon │
1509 │ │ │ reference │
1510 │ │ │ receiver at │
1511 │ │ │ the epoch │
1512 │ │ │ indicated by │
1513 │ │ │ the z_count │
1514 │ │ │ in the │
1515 │ │ │ parent │
1516 │ │ │ record. │
1517 ├──────┼─────────┼─────────────────────────┤
1518 │rrc │ real │ │
1519 │ │ │ The rate of │
1520 │ │ │ change of │
1521 │ │ │ pseudorange │
1522 │ │ │ error in │
1523 │ │ │ meters/sec │
1524 │ │ │ for this │
1525 │ │ │ satellite as │
1526 │ │ │ measured by │
1527 │ │ │ the beacon │
1528 │ │ │ reference │
1529 │ │ │ receiver at │
1530 │ │ │ the epoch │
1531 │ │ │ indicated by │
1532 │ │ │ the z_count │
1533 │ │ │ field in the │
1534 │ │ │ parent │
1535 │ │ │ record. This │
1536 │ │ │ is used to │
1537 │ │ │ calculate │
1538 │ │ │ pseudorange │
1539 │ │ │ errors at │
1540 │ │ │ other │
1541 │ │ │ epochs, if │
1542 │ │ │ required by │
1543 │ │ │ the GPS │
1544 │ │ │ receiver. │
1545 └──────┴─────────┴─────────────────────────┘
1546 User Differential Range Error values are as follows:
1548 Table 19. UDRE values
1550 ┌──┬──────────────────────┐
1551 │0 │ 1-sigma error <= 1m │
1552 ├──┼──────────────────────┤
1553 │1 │ 1-sigma error <= 4m │
1554 ├──┼──────────────────────┤
1555 │2 │ 1-sigma error <= 8m │
1556 ├──┼──────────────────────┤
1557 │3 │ 1-sigma error > 8m │
1558 └──┴──────────────────────┘
1559 Here's an example:
1561 {"class":"RTCM2","type":1,
1563 "station_id":688,"zcount":843.0,"seqnum":5,"length":19,"station_health":6,
1564 "satellites":[
1565 {"ident":10,"udre":0,"iod":46,"prc":-2.400,"rrc":0.000},
1566 {"ident":13,"udre":0,"iod":94,"prc":-4.420,"rrc":0.000},
1567 {"ident":7,"udre":0,"iod":22,"prc":-5.160,"rrc":0.002},
1568 {"ident":2,"udre":0,"iod":34,"prc":-6.480,"rrc":0.000},
1569 {"ident":4,"udre":0,"iod":47,"prc":-8.860,"rrc":0.000},
1570 {"ident":8,"udre":0,"iod":76,"prc":-7.980,"rrc":0.002},
1571 {"ident":5,"udre":0,"iod":99,"prc":-8.260,"rrc":0.002},
1572 {"ident":23,"udre":0,"iod":81,"prc":-8.060,"rrc":0.000},
1573 {"ident":16,"udre":0,"iod":70,"prc":-11.740,"rrc":0.000},
1574 {"ident":30,"udre":0,"iod":4,"prc":-18.960,"rrc":-0.006},
1575 {"ident":29,"udre":0,"iod":101,"prc":-24.960,"rrc":-0.002}
1576 ]}
1577 Type 3: Reference Station Parameters
1579 Here are the payload members of a type 3 (Reference Station
1580 Parameters) message:
1581 Table 20. Reference Station Parameters
1583 ┌─────┬──────┬────────────────────────┐
1584 │Name │ Type │ │
1585 │ │ │ Description │
1586 ├─────┼──────┼────────────────────────┤
1587 │x │ real │ │
1588 │ │ │ ECEF X │
1589 │ │ │ coordinate. │
1590 ├─────┼──────┼────────────────────────┤
1591 │y │ real │ │
1592 │ │ │ ECEF Y │
1593 │ │ │ coordinate. │
1594 ├─────┼──────┼────────────────────────┤
1595 │z │ real │ │
1596 │ │ │ ECEF Z │
1597 │ │ │ coordinate. │
1598 └─────┴──────┴────────────────────────┘
1599 The coordinates are the position of the station, in meters to two
1601 decimal places, in Earth Centred Earth Fixed coordinates. These are
1602 usually referred to the WGS84 reference frame, but may be referred
1603 to NAD83 in the US (essentially identical to WGS84 for all except
1604 geodesists), or to some other reference frame in other parts of the
1605 world.
1606 An invalid reference message is represented by a type 3 header
1608 without payload fields.
1609 Here's an example:
1611 {"class":"RTCM2","type":3,
1613 "station_id":652,"zcount":1657.2,"seqnum":2,"length":4,"station_health":6,
1614 "x":3878620.92,"y":670281.40,"z":5002093.59
1615 }
1616 Type 4: Datum
1618 Here are the payload members of a type 4 (Datum) message:
1619 Table 21. Datum
1621 ┌───────────┬─────────┬────────────────────────┐
1622 │Name │ Type │ │
1623 │ │ │ Description │
1624 ├───────────┼─────────┼────────────────────────┤
1625 │dgnss_type │ string │ │
1626 │ │ │ Either │
1627 │ │ │ "GPS", │
1628 │ │ │ "GLONASS", │
1629 │ │ │ "GALILEO", │
1630 │ │ │ or │
1631 │ │ │ "UNKNOWN". │
1632 ├───────────┼─────────┼────────────────────────┤
1633 │dat │ integer │ │
1634 │ │ │ 0 or 1 and │
1635 │ │ │ indicates │
1636 │ │ │ the sense │
1637 │ │ │ of the │
1638 │ │ │ offset │
1639 │ │ │ shift given │
1640 │ │ │ by dx, dy, │
1641 │ │ │ dz. dat = 0 │
1642 │ │ │ means that │
1643 │ │ │ the station │
1644 │ │ │ coordinates │
1645 │ │ │ (in the │
1646 │ │ │ reference │
1647 │ │ │ message) │
1648 │ │ │ are │
1649 │ │ │ referred to │
1650 │ │ │ a local │
1651 │ │ │ datum and │
1652 │ │ │ that adding │
1653 │ │ │ dx, dy, dz │
1654 │ │ │ to that │
1655 │ │ │ position │
1656 │ │ │ will render │
1657 │ │ │ it in GNSS │
1658 │ │ │ coordinates │
1659 │ │ │ (WGS84 for │
1660 │ │ │ GPS). If │
1661 │ │ │ dat = 1 │
1662 │ │ │ then the │
1663 │ │ │ ref station │
1664 │ │ │ position is │
1665 │ │ │ in GNSS │
1666 │ │ │ coordinates │
1667 │ │ │ and adding │
1668 │ │ │ dx, dy, dz │
1669 │ │ │ will give │
1670 │ │ │ it referred │
1671 │ │ │ to the │
1672 │ │ │ local │
1673 │ │ │ datum. │
1674 ├───────────┼─────────┼────────────────────────┤
1675 │datum_name │ string │ │
1676 │ │ │ A standard │
1677 │ │ │ name for │
1678 │ │ │ the datum. │
1679 ├───────────┼─────────┼────────────────────────┤
1680 │dx │ real │ │
1681 │ │ │ X offset. │
1682 ├───────────┼─────────┼────────────────────────┤
1683 │dy │ real │ │
1684 │ │ │ Y offset. │
1685 ├───────────┼─────────┼────────────────────────┤
1686 │dz │ real │ │
1687 │ │ │ Z offset. │
1688 └───────────┴─────────┴────────────────────────┘
1689 <dx> <dy> <dz> are offsets to convert from local datum to GNSS
1691 datum or vice versa. These fields are optional.
1692 An invalid datum message is represented by a type 4 header without
1694 payload fields.
1695 Type 5: Constellation Health
1697 One or more of these follow the header for type 5 messages — one
1698 for each satellite.
1699 Here is the format:
1701 Table 22. Constellation health
1703 ┌────────────┬─────────┬──────────────────────────┐
1704 │Name │ Type │ │
1705 │ │ │ Description │
1706 ├────────────┼─────────┼──────────────────────────┤
1707 │ident │ integer │ │
1708 │ │ │ The PRN │
1709 │ │ │ number of │
1710 │ │ │ the │
1711 │ │ │ satellite. │
1712 ├────────────┼─────────┼──────────────────────────┤
1713 │iodl │ bool │ │
1714 │ │ │ True │
1715 │ │ │ indicates │
1716 │ │ │ that this │
1717 │ │ │ information │
1718 │ │ │ relates to │
1719 │ │ │ the │
1720 │ │ │ satellite │
1721 │ │ │ information │
1722 │ │ │ in an │
1723 │ │ │ accompanying │
1724 │ │ │ type 1 or │
1725 │ │ │ type 9 │
1726 │ │ │ message. │
1727 ├────────────┼─────────┼──────────────────────────┤
1728 │health │ integer │ 0 indicates that the │
1729 │ │ │ satellite is healthy. │
1730 │ │ │ Any other value │
1731 │ │ │ indicates a │
1732 │ │ │ problem (coding is not │
1733 │ │ │ known)..PP │
1734 ├────────────┼─────────┼──────────────────────────┤
1735 │snr │ integer │ │
1736 │ │ │ The │
1737 │ │ │ carrier/noise │
1738 │ │ │ ratio of the │
1739 │ │ │ received │
1740 │ │ │ signal in │
1741 │ │ │ the range 25 │
1742 │ │ │ to 55 │
1743 │ │ │ dB(Hz). │
1744 ├────────────┼─────────┼──────────────────────────┤
1745 │health_en │ bool │ │
1746 │ │ │ If set to │
1747 │ │ │ True it │
1748 │ │ │ indicates │
1749 │ │ │ that the │
1750 │ │ │ satellite is │
1751 │ │ │ healthy even │
1752 │ │ │ if the │
1753 │ │ │ satellite │
1754 │ │ │ navigation │
1755 │ │ │ data says it │
1756 │ │ │ is unhealthy. │
1757 ├────────────┼─────────┼──────────────────────────┤
1758 │new_data │ bool │ True indicates that the │
1759 │ │ │ IOD for this satellite │
1760 │ │ │ will │
1761 │ │ │ soon be updated │
1762 │ │ │ in type 1 or 9 │
1763 │ │ │ messages..PP │
1764 ├────────────┼─────────┼──────────────────────────┤
1765 │los_warning │ bool │ │
1766 │ │ │ Line-of-sight │
1767 │ │ │ warning. True │
1768 │ │ │ indicates │
1769 │ │ │ that the │
1770 │ │ │ satellite │
1771 │ │ │ will shortly │
1772 │ │ │ go unhealthy. │
1773 ├────────────┼─────────┼──────────────────────────┤
1774 │tou │ integer │ │
1775 │ │ │ Healthy time │
1776 │ │ │ remaining in │
1777 │ │ │ seconds. │
1778 └────────────┴─────────┴──────────────────────────┘
1779 Type 6: Null
1781 This just indicates a null message. There are no payload fields.
1782 Unknown message
1784 This format is used to dump message words in hexadecimal when the
1785 message type field doesn't match any of the known ones.
1786 Here is the format:
1788 Table 23. Unknown Message
1790 ┌─────┬──────┬────────────────────────┐
1791 │Name │ Type │ │
1792 │ │ │ Description │
1793 ├─────┼──────┼────────────────────────┤
1794 │data │ list │ │
1795 │ │ │ A list of │
1796 │ │ │ strings. │
1797 └─────┴──────┴────────────────────────┘
1798 Each string in the array is a hex literal representing 30 bits of
1800 information, after parity checks and inversion. The high two bits
1801 should be ignored.
1802 Type 7: Radio Beacon Almanac
1804 Here is the format:
1805 Table 24. Contellation health
1807 ┌───────────┬─────────┬───────────────────────────┐
1808 │Name │ Type │ │
1809 │ │ │ Description │
1810 ├───────────┼─────────┼───────────────────────────┤
1811 │lat │ real │ │
1812 │ │ │ Latitude in │
1813 │ │ │ degrees, of │
1814 │ │ │ the LF │
1815 │ │ │ transmitter │
1816 │ │ │ antenna for │
1817 │ │ │ the station │
1818 │ │ │ for which │
1819 │ │ │ this is an │
1820 │ │ │ almanac. │
1821 │ │ │ North is │
1822 │ │ │ positive. │
1823 ├───────────┼─────────┼───────────────────────────┤
1824 │lon │ real │ │
1825 │ │ │ Longitude │
1826 │ │ │ in degrees, │
1827 │ │ │ of the LF │
1828 │ │ │ transmitter │
1829 │ │ │ antenna for │
1830 │ │ │ the station │
1831 │ │ │ for which │
1832 │ │ │ this is an │
1833 │ │ │ almanac. │
1834 │ │ │ East is │
1835 │ │ │ positive. │
1836 ├───────────┼─────────┼───────────────────────────┤
1837 │range │ integer │ Published range of the │
1838 │ │ │ station in km..PP │
1839 ├───────────┼─────────┼───────────────────────────┤
1840 │frequency │ real │ │
1841 │ │ │ Station │
1842 │ │ │ broadcast │
1843 │ │ │ frequency │
1844 │ │ │ in kHz. │
1845 ├───────────┼─────────┼───────────────────────────┤
1846 │health │ integer │ │
1847 │ │ │ <health> is │
1848 │ │ │ the health │
1849 │ │ │ of the │
1850 │ │ │ station for │
1851 │ │ │ which this │
1852 │ │ │ is an │
1853 │ │ │ almanac. If │
1854 │ │ │ it is │
1855 │ │ │ non-zero, │
1856 │ │ │ the station │
1857 │ │ │ is issuing │
1858 │ │ │ suspect │
1859 │ │ │ data and │
1860 │ │ │ should not │
1861 │ │ │ be used for │
1862 │ │ │ fixes. The │
1863 │ │ │ ITU and │
1864 │ │ │ RTCM104 │
1865 │ │ │ standards │
1866 │ │ │ differ │
1867 │ │ │ about the │
1868 │ │ │ mode │
1869 │ │ │ detailed │
1870 │ │ │ interpretation │
1871 │ │ │ of the │
1872 │ │ │ <health> │
1873 │ │ │ field and │
1874 │ │ │ even about │
1875 │ │ │ its bit │
1876 │ │ │ width. │
1877 ├───────────┼─────────┼───────────────────────────┤
1878 │station_id │ integer │ │
1879 │ │ │ The id of the │
1880 │ │ │ transmitter. │
1881 │ │ │ This is not │
1882 │ │ │ the same as │
1883 │ │ │ the reference │
1884 │ │ │ id in the │
1885 │ │ │ header, the │
1886 │ │ │ latter being │
1887 │ │ │ the id of the │
1888 │ │ │ reference │
1889 │ │ │ receiver. │
1890 ├───────────┼─────────┼───────────────────────────┤
1891 │bitrate │ integer │ │
1892 │ │ │ The │
1893 │ │ │ transmitted │
1894 │ │ │ bitrate. │
1895 └───────────┴─────────┴───────────────────────────┘
1896 Here's an example:
1898 {"class":"RTCM2","type":9,"station_id":268,"zcount":252.6,
1900 "seqnum":4,"length":5,"station_health":0,
1901 "satellites":[
1902 {"ident":13,"udre":0,"iod":3,"prc":-25.940,"rrc":0.066},
1903 {"ident":2,"udre":0,"iod":73,"prc":0.920,"rrc":-0.080},
1904 {"ident":8,"udre":0,"iod":22,"prc":23.820,"rrc":0.014}
1905 ]}
1906 Type 13: GPS Time of Week
1908 Here are the payload members of a type 13 (Groumf Tramitter
1909 Parameters) message:
1910 Table 25. Grund Transmitter Parameters
1912 ┌──────────┬─────────┬─────────────────────────┐
1913 │Name │ Type │ │
1914 │ │ │ Description │
1915 ├──────────┼─────────┼─────────────────────────┤
1916 │status │ bool │ │
1917 │ │ │ If True, │
1918 │ │ │ signals │
1919 │ │ │ user to │
1920 │ │ │ expect a │
1921 │ │ │ type 16 │
1922 │ │ │ explanatory │
1923 │ │ │ message │
1924 │ │ │ associated │
1925 │ │ │ with this │
1926 │ │ │ station. │
1927 │ │ │ Probably │
1928 │ │ │ indicates │
1929 │ │ │ some sort │
1930 │ │ │ of unusual │
1931 │ │ │ event. │
1932 ├──────────┼─────────┼─────────────────────────┤
1933 │rangeflag │ bool │ │
1934 │ │ │ If True, │
1935 │ │ │ indicates │
1936 │ │ │ that the │
1937 │ │ │ estimated │
1938 │ │ │ range is │
1939 │ │ │ different │
1940 │ │ │ from that │
1941 │ │ │ found in │
1942 │ │ │ the Type 7 │
1943 │ │ │ message │
1944 │ │ │ (which │
1945 │ │ │ contains │
1946 │ │ │ the │
1947 │ │ │ beacon's │
1948 │ │ │ listed │
1949 │ │ │ range). │
1950 │ │ │ Generally │
1951 │ │ │ indicates a │
1952 │ │ │ range │
1953 │ │ │ reduction │
1954 │ │ │ due to │
1955 │ │ │ causes such │
1956 │ │ │ as poor │
1957 │ │ │ ionospheric │
1958 │ │ │ conditions │
1959 │ │ │ or reduced │
1960 │ │ │ transmission │
1961 │ │ │ power. │
1962 ├──────────┼─────────┼─────────────────────────┤
1963 │lat │ real │ │
1964 │ │ │ Degrees │
1965 │ │ │ latitude, │
1966 │ │ │ signed. │
1967 │ │ │ Positive is │
1968 │ │ │ N, negative │
1969 │ │ │ is S. │
1970 ├──────────┼─────────┼─────────────────────────┤
1971 │lon │ real │ │
1972 │ │ │ Degrees │
1973 │ │ │ longitude, │
1974 │ │ │ signed. │
1975 │ │ │ Positive is │
1976 │ │ │ E, negative │
1977 │ │ │ is W. │
1978 ├──────────┼─────────┼─────────────────────────┤
1979 │range │ integer │ │
1980 │ │ │ Transmission │
1981 │ │ │ range in km │
1982 │ │ │ (1-1024). │
1983 └──────────┴─────────┴─────────────────────────┘
1984 This message type replaces message type 3 (Reference Station
1986 Parameters) in RTCM 2.3.
1987 Type 14: GPS Time of Week
1989 Here are the payload members of a type 14 (GPS Time of Week)
1990 message:
1991 Table 26. Reference Station Parameters
1993 ┌─────────┬─────────┬────────────────────────┐
1994 │Name │ Type │ │
1995 │ │ │ Description │
1996 ├─────────┼─────────┼────────────────────────┤
1997 │week │ integer │ │
1998 │ │ │ GPS week │
1999 │ │ │ (0-123). │
2000 ├─────────┼─────────┼────────────────────────┤
2001 │hour │ integer │ │
2002 │ │ │ Hour of │
2003 │ │ │ week │
2004 │ │ │ (0-167). │
2005 ├─────────┼─────────┼────────────────────────┤
2006 │leapsecs │ integer │ │
2007 │ │ │ Leap │
2008 │ │ │ Seconds │
2009 │ │ │ (0-63). │
2010 └─────────┴─────────┴────────────────────────┘
2011 Here's an example:
2013 {"class":"RTCM2","type":14,"station_id":652,"zcount":1657.2,
2015 "seqnum":3,"length":1,"station_health":6,"week":601,"hour":109,
2016 "leapsecs":15}
2017 Type 16: Special Message
2019 Table 27. Special Message
2020 ┌────────┬────────┬────────────────────────┐
2021 │Name │ Type │ │
2022 │ │ │ Description │
2023 ├────────┼────────┼────────────────────────┤
2024 │message │ string │ │
2025 │ │ │ A text │
2026 │ │ │ message │
2027 │ │ │ sent by the │
2028 │ │ │ beacon │
2029 │ │ │ operator. │
2030 └────────┴────────┴────────────────────────┘
2031 Type 31: Correction data
2033 One or more GLONASS satellite objects follow the header for type 1
2034 or type 9 messages. Here is the format:
2035 Table 28. Satellite object
2037 ┌───────┬──────────┬────────────────────────────────┐
2038 │Name │ Type │ │
2039 │ │ │ Description │
2040 ├───────┼──────────┼────────────────────────────────┤
2041 │ident │ integer │ │
2042 │ │ │ The PRN │
2043 │ │ │ number of │
2044 │ │ │ the │
2045 │ │ │ satellite │
2046 │ │ │ for which │
2047 │ │ │ this is │
2048 │ │ │ correction │
2049 │ │ │ data. │
2050 ├───────┼──────────┼────────────────────────────────┤
2051 │udre │ integer │ │
2052 │ │ │ User │
2053 │ │ │ Differential │
2054 │ │ │ Range Error │
2055 │ │ │ (0-3). See │
2056 │ │ │ the table │
2057 │ │ │ following │
2058 │ │ │ for values. │
2059 ├───────┼──────────┼────────────────────────────────┤
2060 │change │ boolean │ │
2061 │ │ │ Change-of-ephemeris │
2062 │ │ │ bit. │
2063 ├───────┼──────────┼────────────────────────────────┤
2064 │tod │ uinteger │ │
2065 │ │ │ Count of 30-second │
2066 │ │ │ periods since the │
2067 │ │ │ top of the hour. │
2068 ├───────┼──────────┼────────────────────────────────┤
2069 │prc │ real │ │
2070 │ │ │ The pseudorange │
2071 │ │ │ error in meters for │
2072 │ │ │ this satellite as │
2073 │ │ │ measured by the │
2074 │ │ │ beacon reference │
2075 │ │ │ receiver at the │
2076 │ │ │ epoch indicated by │
2077 │ │ │ the z_count in the │
2078 │ │ │ parent record. │
2079 ├───────┼──────────┼────────────────────────────────┤
2080 │rrc │ real │ │
2081 │ │ │ The rate of change │
2082 │ │ │ of pseudorange │
2083 │ │ │ error in meters/sec │
2084 │ │ │ for this satellite │
2085 │ │ │ as measured by the │
2086 │ │ │ beacon reference │
2087 │ │ │ receiver at the │
2088 │ │ │ epoch indicated by │
2089 │ │ │ the z_count field │
2090 │ │ │ in the parent │
2091 │ │ │ record. This is │
2092 │ │ │ used to calculate │
2093 │ │ │ pseudorange errors │
2094 │ │ │ at other epochs, if │
2095 │ │ │ required by the GPS │
2096 │ │ │ receiver. │
2097 └───────┴──────────┴────────────────────────────────┘
2098 Here's an example:
2100 {"class":"RTCM2","type":31,"station_id":652,"zcount":1642.2,
2102 "seqnum":0,"length":14,"station_health":6,
2103 "satellites":[
2104 {"ident":5,"udre":0,"change":false,"tod":0,"prc":132.360,"rrc":0.000},
2105 {"ident":15,"udre":0,"change":false,"tod":0,"prc":134.840,"rrc":0.002},
2106 {"ident":14,"udre":0,"change":false,"tod":0,"prc":141.520,"rrc":0.000},
2107 {"ident":6,"udre":0,"change":false,"tod":0,"prc":127.000,"rrc":0.000},
2108 {"ident":21,"udre":0,"change":false,"tod":0,"prc":128.780,"rrc":0.000},
2109 {"ident":22,"udre":0,"change":false,"tod":0,"prc":125.260,"rrc":0.002},
2110 {"ident":20,"udre":0,"change":false,"tod":0,"prc":117.280,"rrc":-0.004},
2111 {"ident":16,"udre":0,"change":false,"tod":17,"prc":113.460,"rrc":0.018}
2112 ]}
2113
2115 The support for RTCM104v3 dumping is incomplete and buggy. Do not
2116 attempt to use it for production! Anyone interested in it should read
2117 the source code.
2118
2120 AIS support is an extension. It may not be present if your instance of
2121 gpsd has been built with a restricted feature set.
2122 AIS packets are dumped as JSON objects with class "AIS". Each AIS
2124 report object contains a "type" field giving the AIS message type and a
2125 "scaled" field telling whether the remainder of the fields are dumped
2126 in scaled or unscaled form. (These will be emitted before any
2127 type-specific fields.) It will also contain a "device" field naming the
2128 data source. Other fields have names and types as specified in the
2129 AIVDM/AIVDO Protocol Decoding document on the GPSD project website;
2130 each message field table may be directly interpreted as a specification
2131 for the members of the corresponding JSON object type.
2132 By default, certain scaling and conversion operations are performed for
2134 JSON output. Latitudes and longitudes are scaled to decimal degrees
2135 rather than the native AIS unit of 1/10000th of a minute of arc. Ship
2136 (but not air) speeds are scaled to knots rather than tenth-of-knot
2137 units. Rate of turn may appear as "nan" if is unavailable, or as one of
2138 the strings "fastright" or "fastleft" if it is out of the AIS encoding
2139 range; otherwise it is quadratically mapped back to the turn sensor
2140 number in degrees per minute. Vessel draughts are converted to decimal
2141 meters rather than native AIS decimeters. Various other scaling
2142 conversions are described in "AIVDM/AIVDO Protocol Decoding".
2143
2145 Subframe support is always compiled into gpsd but many GPSes do not
2146 output subframe data or the gpsd driver may not support subframes.
2147 Subframe packets are dumped as JSON objects with class "SUBFRAME". Each
2149 subframe report object contains a "frame" field giving the subframe
2150 number, a "tSV" field for the transmitting satellite number, a "TOW17"
2151 field containing the 17 MSBs of the start of the next 12-second message
2152 and a "scaled" field telling whether the remainder of the fields are
2153 dumped in scaled or unscaled form. It will also contain a "device"
2154 field naming the data source. Each SUBFRAME object will have a
2155 sub-object specific to that subframe page type. Those sub-object fields
2156 have names and types similar to those specified in the IS-GPS-200E
2157 document; each message field table may be directly interpreted as a
2158 specification for the members of the corresponding JSON object type.
2159
2161 gpsd(8), libgps(3),
2162
2164 The protocol was designed and documented by Eric S. Raymond.
2165
2167 1. Radio Technical Commission for Maritime Services
2168 http://www.rtcm.org/
2169 2. table of leap second corrections
2171 ftp://maia.usno.navy.mil/ser7/tai-utc.dat
2172The GPSD Project 28 Aug 2011 GPSD_JSON(5)