Changes between Version 16 and Version 17 of Processing/SRTMDEMs

Timestamp:

Oct 21, 2010, 2:57:58 PM (14 years ago)

Author:

anch

Comment:

--

Processing/SRTMDEMs

@@ -25 +25 @@
 For ASTER data:
 {{{
-r.in.gdal input=<aster_tile>_dem.tif output=aster_data
+r.in.gdal input=<aster_tile>_dem.tif output=<MAP_NAME>
 }}}
 For SRTM data:
 {{{
-r.in.gdal input=w001001.adf output=srtm_data
+r.in.gdal input=w001001.adf output=<MAP_NAME>
 }}}
 
@@ -36 +36 @@
 If the data you have downloaded spans multiple tiles, then you will need to run the above but inside a for loop like so:
 
+For ASTER data:
 {{{
 for tile in `ls *_dem.tif`;
 do r.in.gdal input=$tile output=$tile.tile;
+done
+}}}
+For SRTM data:
+{{{
+for tile in `ls *.adf`;
+r.in.gdal input=$tile output=$tile.tile;
 done
 }}}
@@ -56 +63 @@
 }}}
 
-I will refer to the comma separated list after "rast=" as TILELIST from hereon - This is the bit you need.
+I will refer to the comma separated list after "rast=" as <TILELIST> from hereon - This is the bit you need.
 
 Now run
 {{{
-g.region rast=TILELIST
+g.region rast=<TILELIST>
 }}}
 
@@ -66 +73 @@
 
 {{{
-r.patch input=TILELIST output=some_name
+r.patch input=<TILELIST> output=<MAP_NAME>
 }}}
 
-Write down some_name somewhere - you will need it in a minute.
+Write down <MAP_NAME> somewhere - you will need it in a minute.
 
 5. Quit Grass and then start it up again. Select a location using UTM projection for the target area or create one if none is available - make sure you've got the right UTM zone. Note you can also use whatever other projection you want, but this guide assumes you want UTM.
@@ -75 +82 @@
 Check [http://www.gpsinformation.org/utm-zones.gif] For the UTM zone
 
-6. Use a conversion utility (eg see the spreadsheet at [http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM#Spreadsheet http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM#Spreadsheet]) to determine the boundaries of the target flight in meters within the selected UTM zone. If the flight spans two or more UTM zones, you will have to calculate the offsets appropriate to work out the east and west boundaries of the area. eg. If western boundary is zone 32 and eastern boundary is zone 33, for eastern value use zone 32, add 750000 to value from spreadsheet 
-to find eastings relative to zone 32 bound.
+6. Here we can use the manual method of calculating the eastings/northings or simply grab them from the tile(s) we have input.
 
-6-alternative.  Once all of the 
+'''Manual:'''
+Use a conversion utility (eg see the spreadsheet at [http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM#Spreadsheet http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM#Spreadsheet]) to determine the boundaries of the target flight in meters within the selected UTM zone. If the flight spans two or more UTM zones, you will have to calculate the offsets appropriate to work out the east and west boundaries of the area. eg. If western boundary is zone 32 and eastern boundary is zone 33, for eastern value use zone 32, add 750000 to value from spreadsheet to find eastings relative to zone 32 bound.
 
-7. Set active region to calculated eastings/northings using:
+7. Set active region to calculated eastings/northings using
+
 {{{
 g.region n=<north val> s=<south val> e=<east val> w=<west val> res=50
 }}}
 
+For ASTER please put res=30
+
 8. Use r.proj to convert from lat/long to UTM:
 {{{
-r.proj input=<input_map_name> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
+r.proj input=<MAP_NAME> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
 }}}
+
+Where <MAP_NAME> is what we created in step 4.
 
 9. If r.proj gives an error saying that the input map is outside the bounds of the current region, go back to step 6 and check your numbers
 
+
+'''Other method:'''
+Set the northings/eastings to something very large e.g.
+
+{{{
+g.region n=50000000 s=0 e=50000000 w=-50000000 res=50
+}}}
+
+For ASTER please put res=30
+
+8. Use r.proj to convert from lat/long to UTM:
+{{{
+r.proj input=<MAP_NAME> location=<lat/long_location> mapset=<lat/long_mapset> output=<output_map_name>
+}}}
+
+Where <MAP_NAME> is what we created in step 4.
+
+9.
+
+Set the new region 
+
+{{{
+g.region rast=<output_map_name>
+}}}
+
+You can run 
+
+{{{
+gis.m &
+}}}
+
+To run a GUI and check whether the DEM covers the correct area, or to make the area smaller.
+
 10 Output ASCII DEM from converted map as normal (see [wiki:Processing/NextMapDEMs Creation of DEMs from NextMap data])