Re: [GRASS-user] Pre-processing LANDSAT TM Orthorectified images from GLCF
Hi,
I have created a simple script to automate the pre-processing process
of landsat tm+. Here it is, if you see it needs improvement (my bash
skill is very rudimentary) please comment:
===
#!/bin/sh -x
# Script to automate pre-processing of LANDSAT ETM+ data
# Requires bands 1-5, 6 7 from
ftp://ftp.glcf.umiacs.umd.edu/glcf/Landsat/WRS2 and also a DEM file
# Requires i.landsat.toar, i.topo.corr, i.landsat.acca module from grass addons
# June 12, 2008
# set the following variables
#original band prefix
BANDPREF=lsat7_2000
#path to metadata
METADATA=/home/maning/pfua/map_data/landsat/glcf_met/p111r054_7x2309.met
#data of image
DATE=2000-03-09
#solar elevation
SUNELV=57.1772505
#sun zenith you can get it from http://www.nrel.gov/midc/solpos/solpos.html
SUNZEN=32.727
#sun azimuth
SUNAZI=112.3801002
#dem file
DEM=dem_90
## nothing to change below
if [ -z $GISBASE ]
then
echo
echo You must be in GRASS GIS to run this program
echo
exit 1
fi
g.region rast=${BANDPREF}.1
# calibrate DN values to top of atmosphere radiance
echo Calibrating to radiance ...
i.landsat.toar -7 -v band_prefix=${BANDPREF} metfile=${METADATA}
echo Imported as '${BANDPREF}.toar.bandnumber'
echo Correcting topographic effects ...
i.topo.corr -i base=${DEM} zenith=${SUNZEN} azimuth=${SUNAZI} out=cosi
i.topo.corr base=cosi
input=${BANDPREF}.toar.1,${BANDPREF}.toar.2,${BANDPREF}.toar.3,${BANDPREF}.toar.4,${BANDPREF}.toar.5,${BANDPREF}.toar.61,${BANDPREF}.toar.7
out=tcor zenith=${SUNZEN} method=c-factor
echo Calculating cloud cover ...
i.landsat.acca -f2s band=tcor.${BANDPREF}.toar out=${BANDPREF}.acca
echo Done!
g.list rast
===
Some notes:
1. Calculation for solar zenith is taken from:
http://www.nrel.gov/midc/solpos/solpos.html
2. DEM for i.topo.corr is the default SRTM resolution (90m), is this okay?
3. i.landsat.cca gives very good results, however, adding the -s flag
(for cloud shadows), sometimes misclassify water bodies such as
rivers.
image: http://farm4.static.flickr.com/3126/2571893895_0a73dd3380.jpg
cheers,
maning
On 6/2/08, maning sambale [EMAIL PROTECTED] wrote:
Markus,
AFAIK LANDSAT is sun-synchronous, it passes in the local morning time
(something like 10:30-11:00).
Maybe this helps:
http://earthobservatory.nasa.gov/MissionControl/overpass.html
Since it is an overpass predictor, it doesn't provide information on
previous landsat overpass. Can I use this as a proxy to the hh:mm for
i.atcorr (me thinks no)? Or set an arbitrary time say between 10:30
to 11:00?
i.atcorr is the sophisticated correction, i.landsat.dehaze only a simple
approach based on image statistics.
3. correction for topographic/terrain effects (most of my study area
are in maountainous regions)
use book 2nd ed. (page 226) cosine correction
using r.sunmask, r.mapcalc
Problem: again, no image acquisition time
(see above). cosine correction is a simple approach. See also
i.topo.corr (from GRASS AddOns).
Thank you for this one.
4. removal of clouds
use i.landsat.acca
https://svn.osgeo.org/grass/grass-addons/imagery/i.landsat.acca/
Never tried, please report back.
Will do, via wiki.
I have collected all this now in
http://grass.osgeo.org/wiki/Image_processing#Preprocessing
Feel free to further improve that Wiki page.
Markus
As usual, thank you very much.
cheers,
maning
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Re: [GRASS-user] Pre-processing LANDSAT TM Orthorectified images from GLCF
On Mon, Jun 2, 2008 at 7:50 AM, maning sambale [EMAIL PROTECTED] wrote: Hi, For a project I am involved with, we are conducting landcover classification from LANDSAT TM (orthorectified) data downloaded from GLCF. We are now in the process on pre-processing the image and then conduct classification using i.smap. Following the GRASS book, we will be conducting the pre-processing steps outlined: 1. calibration from DN to apparent radiance at sensor - gain/bias offsets following grass book 2nd ed. (page 222) r.mapcalc band.rad = ((LMAX - (LMIN))/(255.0 - 1.0)) * (band -1.0) + (LMIN) or i.landsat.toar i.landsat.toar is the more sophisticated approach (or, easier since you don't need to write the formula manuallly). 2. correction for atmospheric effects use i.atcorr problem: the metadata supplied by GLCF does not indicate image acquisition time sample metadata: http://tinyurl.com/6oo428 or use i.landsat.dehaze AFAIK LANDSAT is sun-synchronous, it passes in the local morning time (something like 10:30-11:00). Maybe this helps: http://earthobservatory.nasa.gov/MissionControl/overpass.html i.atcorr is the sophisticated correction, i.landsat.dehaze only a simple approach based on image statistics. 3. correction for topographic/terrain effects (most of my study area are in maountainous regions) use book 2nd ed. (page 226) cosine correction using r.sunmask, r.mapcalc Problem: again, no image acquisition time (see above). cosine correction is a simple approach. See also i.topo.corr (from GRASS AddOns). 4. removal of clouds use i.landsat.acca https://svn.osgeo.org/grass/grass-addons/imagery/i.landsat.acca/ Never tried, please report back. The beauty with GRASS and the GRASS book is that it has the tools/modules I need for this project, however, I find it difficult to choose which one I should use (i.atcoor or i.landsat.dahaze?). Am I following the steps in correct order? Or is it necessary to do all this? Reading from GLCF documentation, they did orthrectification for this image already. Any pointers would be very helpful. I have collected all this now in http://grass.osgeo.org/wiki/Image_processing#Preprocessing Feel free to further improve that Wiki page. Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Pre-processing LANDSAT TM Orthorectified images from GLCF
Markus, AFAIK LANDSAT is sun-synchronous, it passes in the local morning time (something like 10:30-11:00). Maybe this helps: http://earthobservatory.nasa.gov/MissionControl/overpass.html Since it is an overpass predictor, it doesn't provide information on previous landsat overpass. Can I use this as a proxy to the hh:mm for i.atcorr (me thinks no)? Or set an arbitrary time say between 10:30 to 11:00? i.atcorr is the sophisticated correction, i.landsat.dehaze only a simple approach based on image statistics. 3. correction for topographic/terrain effects (most of my study area are in maountainous regions) use book 2nd ed. (page 226) cosine correction using r.sunmask, r.mapcalc Problem: again, no image acquisition time (see above). cosine correction is a simple approach. See also i.topo.corr (from GRASS AddOns). Thank you for this one. 4. removal of clouds use i.landsat.acca https://svn.osgeo.org/grass/grass-addons/imagery/i.landsat.acca/ Never tried, please report back. Will do, via wiki. I have collected all this now in http://grass.osgeo.org/wiki/Image_processing#Preprocessing Feel free to further improve that Wiki page. Markus As usual, thank you very much. cheers, maning -- |-|--| | __.-._ |Ohhh. Great warrior. Wars not make one great. -Yoda | | '-._7' |Freedom is still the most radical idea of all -N.Branden| | /'.-c |Linux registered user #402901, http://counter.li.org/ | | | /T |http://esambale.wikispaces.com| | _)_/LI |-|--| ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
