<div dir="ltr"><br><div style="font-family:arial,sans-serif;font-size:13px">Many thanks for your help. This is the i.landsat.toar command:</div><div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">
<p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'">i.landsat.toar --overwrite input_prefix=LakeChirwaN_B output_prefix=LakeChirwaN_REFL metfile="/Users/xavi/Desktop/Lake Chirwa Landsat /Landsat 7/Level 1 Product/LakeChirwaN/LE71670702002146SGS00_MTL.txt"</span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'"><br></span></p><p class="MsoNormal">and this are the range of values for the first 4 bands. As you can see, all of them includes small negative values, maybe this is the problem. Should I mask them before applying i.atcorr?<br>
</p><p class="MsoNormal"><br></p><p class="MsoNormal"><span style="font-family:'Andale Mono'"><a href="http://r.info/" target="_blank">r.info</a> -r LakeChirwaN_REFL1</span></p><p class="MsoNormal"><span style="font-family:'Andale Mono'">min=-0.0111266691078146</span><br>
</p><p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'">max=0.459205333674142</span></p><p class="MsoNormal"><br></p><p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'"><a href="http://r.info/" target="_blank">r.info</a> -r LakeChirwaN_REFL2 <br>
min=-0.0164141835709247<br>max=0.503966729951046</span></p><p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'"> </span></p><p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'"><a href="http://r.info/" target="_blank">r.info</a> -r LakeChirwaN_REFL3 <br>
min=-0.0133215715423686<br>max=0.465214050321331</span></p><p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'"> </span></p><p class="MsoNormal"></p><p class="MsoNormal"><span lang="EN-GB" style="font-family:'Andale Mono'"><a href="http://r.info/" target="_blank">r.info</a> -r LakeChirwaN_REFL4 <br>
min=-0.023052966150257<br>max=1.0898176742798</span></p><p class="MsoNormal"><br></p><p class="MsoNormal">I have double-checked the parameters of the control file and I did spot an error (the order of the latitude longitude values is inversed), however, correcting this did not solve the problem when I performed te operation again.</p>
<p class="MsoNormal"><br></p><p class="MsoNormal">Others values seems to be OK (the time value is the time provided in the metadata file converted to decimal time, and, according to the GRASS manual 0 value should be entered for visibility when an estimate for aerosol optical depth is available (I obtained this estimate from MODIS MOD08-Gridded Atmospheric Product. </p>
</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2014/1/7 Markus Neteler <span dir="ltr"><<a href="mailto:neteler@osgeo.org" target="_blank">neteler@osgeo.org</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Mon, Jan 6, 2014 at 11:11 PM, Xavier de Lamo <<a href="mailto:xavi.delamo@gmail.com">xavi.delamo@gmail.com</a>> wrote:<br>
> Dear all,<br>
><br>
> I am recent GRASS GIS user who is trying to run the i.atcorr module to<br>
> atmospherically correct a Landsat ETM+ image in GRASS 7 (on MacBook Pro,<br>
> Mavericks OSX). This image has been already converted to reflectance with<br>
> i.landsat. toar.<br>
<br>
</div>Could you please post here the range values of the first four<br>
channels? Something like<br>
<a href="http://r.info" target="_blank">r.info</a> -r channelX<br>
(or use the GUI)<br>
<br>
Just to be sure that the i.landsat. toar output is right.<br>
<div class="im"><br>
> I also use a DEM file obtained from ASTER GDEM. All these<br>
> files are projected to UTM zone 36 S.<br>
> I have followed the steps described in the manual and everything seems to be<br>
> fine except that the process returns an empty raster (all raster values<br>
> equal to NoData).<br>
><br>
> This is the command:<br>
<br>
</div>Please also post the i.landsat.toar command here.<br>
<div class="im"><br>
<br>
> i.atcorr –r –a input= LakeChirwaN-REFL1@Malawi<br>
> parameters=/Users/Xavi/Desktop/LCDM.txt output=LakeChirwaN_REFL1_ATCORR<br>
><br>
> And the LCDM file looks like this:<br>
><br>
><br>
><br>
> 8 -- Landsat ETM+<br>
> 5 26 7.487 35.753 -14.414 -- month day hh.ddd longitude latitude<br>
<br>
</div>Is the order of longitude and latitude right?<br>
The hh.ddd is in correct GMT?<br>
<div class="im"><br>
> 1 -- Atmospheric model: tropical<br>
> 0 -- Visibility<br>
<br>
</div>Zero visibility mean full darkness? :-)<br>
<div class="im"><br>
> -0.009 -- Aerosol Optical Depth 550 nm<br>
> -0.650 -- Mean target elevation (in Km) *-1<br>
> -1000 -- Sensor height (on board a satellite)<br>
><br>
> 61 -- Sensor band (ETM+ band 1)<br>
><br>
> Could someone give help me on this please?<br>
<br>
</div>Please doublecheck the parameters in the control file.<br>
<span class="HOEnZb"><font color="#888888"><br>
Markus<br>
</font></span></blockquote></div><br></div>