1g.region(1) Grass User's Manual g.region(1)
2
6 g.region - Program to manage the boundary definitions for the geo‐
7 graphic region.
8
10 general
11
13 g.region
14 g.region help
15 g.region [-dplecmau3gb] [region=name] [rast=name[,name,...]]
16 [rast3d=name] [vect=name] [3dview=name] [n=value] [s=value]
17 [e=value] [w=value] [t=value] [b=value] [res=value]
18 [res3=value] [nsres=value] [ewres=value] [tbres=value]
19 [zoom=name] [align=name] [save=name] [--overwrite]
20 Flags:
22 -d Set from default region
23 -p Print the current region
25 -l Print the current region in lat/long on current ellipsoid/datum
27 -e Print the current region extent
29 -c Print the current region map center coordinates
31 -m Print region resolution in meters (geodesic)
33 -a Align region to resolution (default = align to bounds, works only
35 for 2D resolution )
36 -u Do not update the current region
38 -3 Print also 3D settings
40 -g Print the current region (shell script style)
42 -b Print the maximum bounding box in lat/long on WGS84 (-g mode only)
44 --overwrite
46 Parameters:
48 region=name
49 Set current region from named region
50 rast=name[,name,...]
52 Set region to match this raster map
53 rast3d=name
55 Set region to match this 3D raster map (both 2D and 3D values)
56 vect=name
58 Set region to match this vector map
59 3dview=name
61 Set region to match this 3dview file
62 n=value
64 Value for the northern edge (format dd:mm:ss{N|S})
65 s=value
67 Value for the southern edge (format dd:mm:ss{N|S})
68 e=value
70 Value for the eastern edge (format ddd:mm:ss{E|W})
71 w=value
73 Value for the western edge (format ddd:mm:ss{E|W})
74 t=value
76 Value for the top edge
77 b=value
79 Value for the bottom edge
80 res=value
82 Grid resolution 2D (both north-south and east-west)
83 res3=value
85 3D grid resolution (north-south, east-west and top-bottom)
86 nsres=value
88 North-south grid resolution 2D (format dd:mm:ss)
89 ewres=value
91 East-west grid resolution 2D (format dd:mm:ss)
92 tbres=value
94 Top-bottom grid resolution 3D
95 zoom=name
97 Raster map to zoom into
98 align=name
100 Raster map to align to
101 save=name
103 Save the current region to region definition file
104
106 The g.region program allows the user to manage the settings of the cur‐
107 rent geographic region. These regional boundaries can be set by the
108 user directly and/or set from a region definition file (stored under
109 the windows directory in the user's current mapset). The user can cre‐
110 ate, modify, and store as many geographic region definitions as desired
111 for any given mapset. However, only one of these geographic region
112 definitions will be current at any given moment, for a specified
113 mapset; i.e., GRASS programs that respect the geographic region set‐
114 tings will use the current geographic region settings.
115
117 Region:
118 In GRASS, a region refers to a geographic area with some defined
119 boundaries, based on a specific map coordinate system and map
120 projection. Each region also has associated with it the spe‐
121 cific east-west and north-south resolutions of its smallest
122 units (rectangular units called "cells").
123 The region's boundaries are given as the northernmost, southernmost,
125 easternmost, and westernmost points that define its extent. The north
126 and south boundaries are commonly called northings, while the east and
127 west boundaries are called eastings.
128 The region's cell resolution defines the size of the smallest piece of
130 data recognized (imported, analyzed, displayed, stored, etc.) by GRASS
131 programs affected by the current region settings. The north-south and
132 east-west cell resolutions need not be the same, thus allowing non-
133 square data cells to exist.
134 Default Region:
136 Each GRASS LOCATION_NAME has a fixed geographic region, called
137 the default geographic region (stored in the region file
138 DEFAULT_WIND under the special mapset PERMANENT), that defines
139 the extent of the data base. While this provides a starting
140 point for defining new geographic regions, user-defined geo‐
141 graphic regions need not fall within this geographic region.
142 Current Region:
144 Each mapset has a current geographic region. This region
145 defines the geographic area in which all GRASS displays and
146 analyses will be done. Data will be resampled, if necessary, to
147 meet the cell resolutions of the current geographic region set‐
148 ting.
149 Region Data Base:
151 Each GRASS MAPSET may contain any number of pre-defined, and
152 named, geographic regions. These region definitions are stored
153 in the user's current mapset location under the windows direc‐
154 tory (also referred to as the user's data base of region defini‐
155 tions). Any of these pre-defined geographic regions may be
156 selected, by name, to become the current geographic region.
157 Users may also access saved region definitions stored under
158 other mapsets in the current location, if these mapsets are
159 included in the user's mapset search path.
160
162 Most of the options will require the user to edit a geographic region,
163 be it the current geographic region or one stored in the user's data
164 base of region definitions (the windows directory). A standard prompt
165 is used to perform this edit. An example is shown below:
166 ---------------------------------------------------------------
167 | IDENTIFY REGION |
168 | |
169 | =========== DEFAULT REGION ========== |
170 | | Default North: 3402025.00 | |
171 | | | |
172 | | ===YOUR REGION=== | |
173 | | | NORTH EDGE | | |
174 | | | 3402025.00_ | | |
175 | | | | | |
176 | Def West: |WEST EDGE | |EAST EDGE | Def.East: |
177 | 233975.00 |233975.00_| |236025.00_| 236025.00 |
178 | | | SOUTH EDGE | | |
179 | | | 3399975.00_ | | |
180 | | ================= | |
181 | | | |
182 | | Default South: 3399975.00 | |
183 | ======================================= |
184 | |
185 | Default GRID RESOLUTION Region |
186 | 50.00 --- East-West --- 50.00__ |
187 | 50.00 -- North-South -- 50.00__ |
188 | |
189 | |
190 | AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE |
191 ---------------------------------------------------------------
192 The fields NORTH EDGE, SOUTH EDGE, WEST EDGE and EAST EDGE, are the
193 boundaries of the geographic region that the user can change. The
194 fields Default North, Default South, Def West and Def East are the
195 boundaries of the default geographic region that are displayed for ref‐
196 erence and cannot be changed. The two GRID RESOLUTION Region fields
197 (east-west, and north-south) are the geographic region's cell resolu‐
198 tions that the user can change. The two GRID RESOLUTION Default fields
199 list the resolutions of the default geographic region; these are dis‐
200 played for reference and cannot be changed here by the user.
201
203 1 Modify the current geographic region directly Allows the user to
204 edit the current region.
205 2 Set current geographic region from default region Copies the
207 default region to the current geographic region, and then lets
208 the user edit the current geographic region.
209 3 Set current geographic region from a data base geographic region
211 Allows the user to select a geographic region by name from the
212 data base of geographic regions to become the current geographic
213 region, and then lets the user edit the current geographic
214 region.
215 Note: geographic region definition files may be selected from other
217 mapsets as well, if accessible and in the user's mapset search path.
218 4 Set current geographic region from a raster (cell) map layer
220 Allows the user to select a raster map layer, copies the cell
221 header for this map layer to the current geographic region, and
222 then lets the user edit the current geographic region. This
223 option is useful when subsequent GRASS operations will be used
224 to produce a raster map layer from one input raster map layer
225 and it is necessary that the result coincide with the input
226 raster map layer.
227 5 Save the current geographic region (window) in the data base
229 Allows the user to save the current geographic region settings
230 in the user's data base of such settings. These files are
231 stored in the windows directory under the user's current mapset.
232 This option is useful when the current geographic region is set
233 directly using option 2, or even by another GRASS program (e.g.,
234 d.m). This option installs an otherwise temporary geographic
235 region setting into the geographic region definition data base
236 for recall when needed.
237 6 Create a new data base geographic region setting Creates a new
239 geographic region definition in the user's data base of such
240 settings in the windows directory under the current mapset,
241 using the geographic region edit prompt described above. After
242 the geographic region definition is created, the user is asked
243 if this geographic region setting should also be used as the
244 current geographic region.
245 7 Modify a data base geographic region setting Modifies a geo‐
247 graphic region setting (in the data base of such settings in the
248 windows directory of the current mapset), using the geographic
249 region edit prompt. After the changes have been made, the user
250 is asked if this geographic region setting should also be used
251 as the current geographic region.
252
254 Alternately, the user can modify the settings of the current geographic
255 region by specifying all needed parameters on the command line. The
256 user enters the command g.region parms, where parms are the following
257 parameters and/or flags:
258
260 g.region n=7360100 e=699000
262 will reset the northing and easting for the current region, but
263 leave the south edge, west edge, and the region cell resolutions
264 unchanged.
265 g.region n=51:36:05N e=10:10:05E s=51:29:55N w=9:59:55E res=0:00:01
268 will reset the northing, easting, southing, westing and resolution for
269 the current region, here in DMS latitude-longitude style (but also dec‐
270 imal degrees can be used).
271 g.region -dp s=698000
274 will set the current region from the default region for the GRASS data
275 base location, reset the south edge to 698000, and then print the
276 result.
277 g.region n=n+1000 w=w-500
280 The n=value may also be specified as a function of its current value:
281 n=n+value increases the current northing, while n=n-value decreases it.
282 This is also true for s=value, e=value, and w=value. In this example
283 the current region's northern boundary is extended by 1000 units and
284 the current region's western boundary is decreased by 500 units.
285 g.region n=s+1000 e=w+1000
288 This form allows the user to set the region boundary values relative
289 to one another. Here, the northern boundary coordinate is set equal to
290 1000 units larger than the southern boundary's coordinate value, and
291 the eastern boundary's coordinate value is set equal to 1000 units
292 larger than the western boundary's coordinate value. The corresponding
293 forms s=n-value and
294 w=e-value may be used to set the values of the region's southern and
296 western boundaries, relative to the northern and eastern boundary val‐
297 ues.
298 g.region rast=soils
299 This form will make the current region settings exactly the same as
300 those given in the cell header file for the raster map layer soils.
301 g.region -up rast=soils
304 The -u option suppresses the re-setting of the current region defini‐
305 tion. This can be useful when it is desired to only extract region
306 information. In this case, the cell header file for the soils map
307 layer is printed without changing the current region settings.
308 g.region -p rast=soils
311 This will zoom into the smallest region which encompasses all non-zero
312 soils data values, and save the new region settings in a file to be
313 called soils and stored under the windows directory in the user's cur‐
314 rent mapset. The current region settings are not changed.
315 g.region b=0 t=3000 tbres=200 res3=100
318 g.region -p3
319 This will define the 3D region for voxel computations. In this exam‐
320 ple a volume with bottom (0m) to top (3000m) at horizontal resolution
321 (100m) and vertical resolution (200m) is defined.
322 g.region -p
325 This will print the current region in the format:
326 projection: 1 (UTM)
327 zone: 13
328 datum: nad27
329 ellipsoid: clark66
330 north: 4928000
331 south: 4914000
332 west: 590000
333 east: 609000
334 nsres: 20
335 ewres: 20
336 rows: 700
337 cols: 950
338 g.region -p3
342 This will print the current region and the 3D region (used for voxels)
343 in the format:
344 projection: 1 (UTM)
345 zone: 13
346 datum: nad27
347 ellipsoid: clark66
348 north: 4928000
349 south: 4914000
350 west: 590000
351 east: 609000
352 top: 1.00000000
353 bottom: 0.00000000
354 nsres: 20
355 nsres3: 20
356 ewres: 20
357 ewres3: 20
358 tbres: 1
359 rows: 700
360 rows3: 700
361 cols: 950
362 cols3: 950
363 depths: 1
364 g.region -g
368 The -g option prints the region in the following script style
369 (key=value) format:
370 n=4928000
371 s=4914000
372 w=590000
373 e=609000
374 nsres=20
375 ewres=20
376 rows=700
377 cols=950
378 g.region -bg
382 The -bg option prints the region in the following script style
383 (key=value) format plus the boundary box in latitude-longitude/WGS84:
384 n=4928000
385 s=4914000
386 w=590000
387 e=609000
388 nsres=20
389 ewres=20
390 rows=700
391 cols=950
392 LL_W=-103.87080682
393 LL_E=-103.62942884
394 LL_N=44.50164277
395 LL_S=44.37302019
396 g.region -l
400 The -l option prints the region in the following format:
401 long: -103.86789484 lat: 44.50165890 (north/west corner)
402 long: -103.62895703 lat: 44.49904013 (north/east corner)
403 long: -103.63190061 lat: 44.37303558 (south/east corner)
404 long: -103.87032572 lat: 44.37564292 (south/west corner)
405 rows: 700
406 cols: 950
407 Center longitude: 103:44:59.170374W [-103.74977]
408 Center latitude: 44:26:14.439781N [44.43734]
409 g.region -pm
413 This will print the current region in the format (latitude-longitude
414 location):
415 projection: 3 (Latitude-Longitude)
416 zone: 0
417 ellipsoid: wgs84
418 north: 90N
419 south: 40N
420 west: 20W
421 east: 20E
422 nsres: 928.73944902
423 ewres: 352.74269109
424 rows: 6000
425 cols: 4800
426 Note that the resolution is here reported in meters, not decimal
427 degrees.
428 The -p (or -g) option is recognized last. This means that all changes
430 are applied to the region settings before printing occurs.
431
433 After all updates have been applied, the current region's southern and
434 western boundaries are (silently) adjusted so that the north/south dis‐
435 tance is a multiple of the north/south resolution and that the
436 east/west distance is a multiple of the east/west resolution.
437 With the -a flag all four boundaries are adjusted to be even multiples
439 of the resolution.
440 The -m flag will report the region resolution in meters. The resolution
442 is calculated by averaging the resolution at the region boundaries.
443 This resolution is calculated by dividing the geodesic distance in
444 meters at the boundary by the number of rows or columns. For example
445 the east / west resolution (ewres) is determined from an average of the
446 geodesic distances at the North and South boundaries divided by the
447 number of columns.
448
450 d.zoom
451 g.access
452 g.mapsets
453 g.projinfo
454
456 Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
457 Last changed: $Date: 2005/12/22 14:37:05 $
459 Full index
461GRASS 6.2.2 g.region(1)