1i.atcorr(1) Grass User's Manual i.atcorr(1)
2
6 i.atcorr - 6s - Second Simulation of Satellite Signal in the Solar
7 Spectrum.
8
11 i.atcorr
12 i.atcorr help
13 i.atcorr [-frabo] iimg=name [iscl=Input scale range] [ialt=name]
14 [ivis=name] icnd=name oimg=name oscl=Output scale range [--overwrite]
15 [--verbose] [--quiet]
16 Flags:
18 -f
19 Output raster is floating point
20 -r
22 Input map converted to reflectance (default is radiance)
23 -a
25 Input from ETM+ image taken after July 1, 2000
26 -b
28 Input from ETM+ image taken before July 1, 2000
29 -o
31 Try to increase computation speed when categorized altitude or/and
32 visibility map is used.
33 --overwrite
35 Allow output files to overwrite existing files
36 --verbose
38 Verbose module output
39 --quiet
41 Quiet module output
42 Parameters:
44 iimg=name
45 Input imagery map to be corrected
46 iscl=Input scale range
48 Input imagery range [0,255]
49 Default: 0,255
50 ialt=name
52 Input altitude map in m (optional)
53 Default: dem_float
54 ivis=name
56 Input visibility map in km (optional)
57 icnd=name
59 6S input text file
60 oimg=name
62 6S output imagery map
63 oscl=Output scale range
65 Rescale output imagery map [0,255]
66 Default: 0,255
67
69 i.atcorr performs atmospheric correction on the input raster using the
70 6S algorithm (Second Simulation of Satellite Signal in the Solar Spec‐
71 trum). A detailed algorithm description is available at the Land Sur‐
72 face Reflectance Science Computing Facility website and Mauro A. Homem
73 Antunes <a href="http://www.ltid.inpe.br/dsr/mauro/6s/down‐
74 load_6s.html">website about his 6s version.
75 Current region settings are ignored. The region is adjusted to cover
77 the input raster before the atmospheric correction is performed. This
78 should not affect the user's current region settings.
79 Because using a continuous elevation ialt or visibility ivis map makes
81 execution time much longer, it is advised to use categorized maps
82 instead, in conjuction with flag -o. This flag tells i.atcorr to try
83 and speedup calculations. However, this option under certain conditions
84 can make execution time longer.
85 If flag -r is used, the input data are treated as reflectance. Other‐
87 wise, the input data are treated as radiance values and are converted
88 to reflectance at the i.atcorr runtime. The output data are always
89 reflectance.
90 An example 6s parameters icnd file for i.atcorr:
92 8 - geometrical conditions=Landsat ETM+
95 2 19 13.00 -47.410 -20.234 - month day hh.ddd longitude lattitude
96 ("hh.ddd" is a decimal hour GMT)
97 1 - atmospheric mode=tropical
98 1 - aerosols model=continental
99 15 - visibility [km] (aerosol model concen‐
100 tration)
101 -.600 - target at 600m above sea level
102 -1000 - sensor on board a satellite
103 64 - 4th band of ETM+ Landsat 7
104
107 1. Using the target elevation and visibility parameters in the icnd
108 file overrides ialt and ivis input rasters. It is not clear what to do
109 to force i.atcorr to use the rasters instead though.
110 2. The "example 6s parameters file" explains that "-.600" in line 6
112 means "target at 600 m ASL". However, in the section E of "6S CODE
113 PARAMETER CHOICES" it reads: "xps <=0. means the target is at the sea
114 level". This is contrary.
115 3. In section E, I'm not sure if the "-100< xpp <0" shouldn't actually
117 be "-1000< xpp <0". ?
118 4. It is not explained what is the "iaer" parameter that section D
120 refers to.
121 5. Section D's "Aerosol model concentration" title could use a better
123 wording I suppose. The current one seems to mean "the concentration of
124 the model of the aerosol". Should it be "Aerosol concentration model"?
125 6. It should be explained under what circumstances the use of catego‐
127 rized maps in conjuction with flag -o can slow down the calculations
128 instead of speeding them up.
129 7. "This should not affect the user's current region settings" sounds
131 ambigious.
132
134 A. Geometrical conditions:
135 | Code | Description | Details
136 | 1 | meteosat observation | enter month,day,decimal hour (universal
137 time-hh.ddd)
138 n. of column,n. of line.(full scale 5000*2500)
140 | 2 | goes east observation | enter month,day,decimal hour (universal
141 time-hh.ddd)
142 n. of column,n. of line.(full scale 17000*12000)c
144 | 3 | goes west observation | enter month,day,decimal hour (universal
145 time-hh.ddd)
146 n. of column,n. of line.(full scale 17000*12000)
148 | 4 | avhrr (PM noaa) | enter month,day,decimal hour (universal time-
149 hh.ddd)
150 n. of column(1-2048),xlonan,hna
152 give long.(xlonan) and overpass hour (hna) at
154 the ascendant node at equator
156 | 5 | avhrr (AM noaa) | enter month,day,decimal hour (universal time-
157 hh.ddd)
158 n. of column(1-2048),xlonan,hna
160 give long.(xlonan) and overpass hour (hna) at
162 the ascendant node at equator
164 | 6 | hrv (spot) | enter month,day,hh.ddd,long.,lat. *
165 | 7 | tm (landsat) | enter month,day,hh.ddd,long.,lat. *
166 | 8 | etm+ (landsat7) | enter month,day,hh.ddd,long.,lat. * * NOTE: for
167 hrv, tm and etm+ experiments, longitude and lattitude are the coordi‐
168 nates of the scene center. Lattitude must be >0 for northern hemisphere
169 and 0 for eastern hemisphere and <0 for western.
170 B. Atmospheric model
172 | Code | Meaning
173 | 0 | no gaseous absorption
174 | 1 | tropical
175 | 2 | midlatitude summer
176 | 3 | midlatitude winter
177 | 4 | subarctic summer
178 | 5 | subarctic winter
179 | 6 | us standard 62
180 | 7 | Define your own atmospheric model as a set of the following 5
181 parameters per each measurement:
182 altitude [km]
183 pressure [mb]
184 temperature [k]
185 h2o density [g/m3]
186 o3 density [g/m3]
187 For example: there is one radiosonde measurement for each altitude of
188 0-25km at a step of 1km, one measurment for each altitude of 25-50km at
189 a step of 5km, and two single measurements for altitudes 70km and
190 100km. This makes 34 measurments. In that case, there are 34*5 values
191 to input.
192 | 8 | Define your own atmospheric model providing values of the water
193 vapor and ozone content:
194 uw [g/cm2]
195 uo3 [cm-atm]
196 The profile is taken from us62.
197 C. Aerosols model
199 | Code | Meaning | Details
200 | 0 | no aerosols |
201 | 1 | continental model |
202 | 2 | maritime model |
203 | 3 | urban model |
204 | 4 | shettle model for background desert aerosol |
205 | 5 | biomass burning |
206 | 6 | stratospheric model |
207 | 7 | define your own model | Enter the volumic percentage of each com‐
208 ponent:
209 c(1) = volumic % of dust-like
210 c(2) = volumic % of water-soluble
211 c(3) = volumic % of oceanic
212 c(4) = volumic % of soot
213 All values between 0 and 1.
214 | 8 | define your own model | Size distribution function: Multimodal
215 Log Normal (up to 4 modes).
216 | 9 | define your own model | Size distribution function: Modified
217 gamma.
218 | 10 | define your own model | Size distribution function: Junge Power-
219 Law.
220 | 11 | define your own model | Sun-photometer measurements, 50 values
221 max, entered as:
222 r and d V / d (logr)
223 where r is the radius [micron], V is the volume, d V / d (logr)
224 [cm3/cm2/micron].
225 Followed by:
226 nr and ni for each wavelength
227 where nr and ni are respectively the real and imaginary part of the
228 refractive index.
229 D. Aerosol model concentration (visibility)
231 If you have an estimate of the meteorological parameter visibility v,
232 enter directly the value of v [km] (the aerosol optical depth will be
233 computed from a standard aerosol profile).
234 If you have an estimate of aerosol optical depth, enter v=0 for the
236 visibility and enter the aerosol optical depth at 550nm.
237 NOTE: if iaer=0, enter v=-1.
239 E. Target altitude (xps), sensor platform (xpp)
241 xps <=0 means the target is at the sea level.
242 xps >0 means you know the altitude of the target expressed in km, and
243 you put that value as xps.
244 xpp=-1000 means that the sensor is on board a satellite.
245 xpp=0 means that the sensor is at the ground level.
246 -100<xpp<0 means you know the altitude of the sensor expressed in kilo‐
247 meters; this altitude is relative to the target altitude.
248 For aircraft simulations only (xpp is neither 0 nor -1000): puw,po3
250 (water vapor content,ozone content between the aircraft and the sur‐
251 face)
252 taerp (the aerosol optical thickness at 550nm between the aircraft and
253 the surface)
254 If these data are not available, enter negative values for all of them.
256 puw,po3 will then be interpolated from the us62 standard profile
257 according to the values at the ground level. taerp will be computed
258 according to a 2km exponential profile for aerosol.
259 F. Sensor band
261 There are two possibilities: either define your own spectral conditions
262 (codes -2, -1, 0, or 1) or choose a code indicating the band of one of
263 the pre-defined satellites.
264 Define your own spectral conditions:
266 | Code | Meaning
268 | -2 | Enter wlinf, wlsup.
269 The filter function will be equal to 1 over the whole band (as iwave=0)
270 but step by step output will be printed.
271 | -1 | Enter wl (monochr. cond, gaseous absorption is included).
272 | 0 | Enter wlinf, wlsup.
273 The filter function will be equal to 1over the whole band.
274 | 1 | Enter wlinf, wlsup and user's filter function s(lambda) by step
275 of 0.0025 micrometer.
276 Pre-defined satellite bands:
278 | Code | Meaning
280 | 2 | meteosat vis band (0.350-1.110)
281 | 3 | goes east band vis (0.490-0.900)
282 | 4 | goes west band vis (0.490-0.900)
283 | 5 | avhrr (noaa6) band 1 (0.550-0.750)
284 | 6 | avhrr (noaa6) band 2 (0.690-1.120)
285 | 7 | avhrr (noaa7) band 1 (0.500-0.800)
286 | 8 | avhrr (noaa7) band 2 (0.640-1.170)
287 | 9 | avhrr (noaa8) band 1 (0.540-1.010)
288 | 10 | avhrr (noaa8) band 2 (0.680-1.120)
289 | 11 | avhrr (noaa9) band 1 (0.530-0.810)
290 | 12 | avhrr (noaa9) band 1 (0.680-1.170)
291 | 13 | avhrr (noaa10) band 1 (0.530-0.780)
292 | 14 | avhrr (noaa10) band 2 (0.600-1.190)
293 | 15 | avhrr (noaa11) band 1 (0.540-0.820)
294 | 16 | avhrr (noaa11) band 2 (0.600-1.120)
295 | 17 | hrv1 (spot1) band 1 (0.470-0.650)
296 | 18 | hrv1 (spot1) band 2 (0.600-0.720)
297 | 19 | hrv1 (spot1) band 3 (0.730-0.930)
298 | 20 | hrv1 (spot1) band pan (0.470-0.790)
299 | 21 | hrv2 (spot1) band 1 (0.470-0.650)
300 | 22 | hrv2 (spot1) band 2 (0.590-0.730)
301 | 23 | hrv2 (spot1) band 3 (0.740-0.940)
302 | 24 | hrv2 (spot1) band pan (0.470-0.790)
303 | 25 | tm (landsat5) band 1 (0.430-0.560)
304 | 26 | tm (landsat5) band 2 (0.500-0.650)
305 | 27 | tm (landsat5) band 3 (0.580-0.740)
306 | 28 | tm (landsat5) band 4 (0.730-0.950)
307 | 29 | tm (landsat5) band 5 (1.5025-1.890)
308 | 30 | tm (landsat5) band 7 (1.950-2.410)
309 | 31 | mss (landsat5) band 1 (0.475-0.640)
310 | 32 | mss (landsat5) band 2 (0.580-0.750)
311 | 33 | mss (landsat5) band 3 (0.655-0.855)
312 | 34 | mss (landsat5) band 4 (0.785-1.100)
313 | 35 | MAS (ER2) band 1 (0.5025-0.5875)
314 | 36 | MAS (ER2) band 2 (0.6075-0.7000)
315 | 37 | MAS (ER2) band 3 (0.8300-0.9125)
316 | 38 | MAS (ER2) band 4 (0.9000-0.9975)
317 | 39 | MAS (ER2) band 5 (1.8200-1.9575)
318 | 40 | MAS (ER2) band 6 (2.0950-2.1925)
319 | 41 | MAS (ER2) band 7 (3.5800-3.8700)
320 | 42 | MODIS band 1 (0.6100-0.6850)
321 | 43 | MODIS band 2 (0.8200-0.9025)
322 | 44 | MODIS band 3 (0.4500-0.4825)
323 | 45 | MODIS band 4 (0.5400-0.5700)
324 | 46 | MODIS band 5 (1.2150-1.2700)
325 | 47 | MODIS band 6 (1.6000-1.6650)
326 | 48 | MODIS band 7 (2.0575-2.1825)
327 | 49 | avhrr (noaa12) band 1 (0.500-1.000)
328 | 50 | avhrr (noaa12) band 2 (0.650-1.120)
329 | 51 | avhrr (noaa14) band 1 (0.500-1.110)
330 | 52 | avhrr (noaa14) band 2 (0.680-1.100)
331 | 53 | POLDER band 1 (0.4125-0.4775)
332 | 54 | POLDER band 2 (non polar) (0.4100-0.5225)
333 | 55 | POLDER band 3 (non polar) (0.5325-0.5950)
334 | 56 | POLDER band 4 P1 (0.6300-0.7025)
335 | 57 | POLDER band 5 (non polar) (0.7450-0.7800)
336 | 58 | POLDER band 6 (non polar) (0.7000-0.8300)
337 | 59 | POLDER band 7 P1 (0.8100-0.9200)
338 | 60 | POLDER band 8 (non polar) (0.8650-0.9400)
339 | 61 | etm+ (landsat7) band 1 (0.435-0.520)
340 | 62 | etm+ (landsat7) band 2 (0.506-0.621)
341 | 63 | etm+ (landsat7) band 3 (0.622-0.702)
342 | 64 | etm+ (landsat7) band 4 (0.751-0.911)
343 | 65 | etm+ (landsat7) band 5 (1.512-1.792)
344 | 66 | etm+ (landsat7) band 7 (2.020-2.380)
345 | 67 | etm+ (landsat7) band 8 (0.504-0.909)
346
348 Original version of the program for GRASS 5:
349 Christo Zietsman, 13422863(at)sun.ac.za
350 Code clean-up and port to GRASS 6.3, 15.12.2006:
352 Yann Chemin, ychemin(at)gmail.com
353
355 Vermote, E.F., Tanre, D., Deuze, J.L., Herman, M., and Morcrette, J.J.,
356 1997, Second simulation of the satellite signal in the solar spectrum,
357 6S: An overview., IEEE Trans. Geosc. and Remote Sens. 35(3):675-686.
358 6s homepage of the Land Surface Reflectance Science Computing Facility
360 Mauro A. Homem Antunes website about his 6s version
362 Last changed: $Date: 2007-09-07 19:38:42 +0200 (Fri, 07 Sep 2007) $
364 Full index
366 © 2003-2008 GRASS Development Team
368GRASS 6.3.0 i.atcorr(1)