Changes between Version 9 and Version 10 of Processing/NextMapDEMs

Timestamp:

Sep 2, 2008, 10:41:08 AM (16 years ago)

Author:

mggr

Comment:

--

Processing/NextMapDEMs

@@ -1 +1 @@
 = Creation of DEMs from NextMap data =
 
-(fast notes)
+The azgcorr format is plain ASCII text, with decimal numbers separated by spaces, one row per row of the DEM.  At the top of the file, you need a single line that describes the geographic position of the DEM.
 
-load arc files into grass
- * import->raster->gdal
- * pick file
- * choose create new location if this is the first import
- * run (will fail for UK as it needs user input)
- * copy and paste command into grass shell so you can respond (e.g. `r.in.gdal -e input=/data/aegean1/nextmap_dems/neodc/by_tile/by_product/dsm/nk/nk02/nk02dsm/w001001.adf output=nk02`
- * if you need to import multiple rasters, you can use the location created, but must select extend region
- * (need to figure out how to join rasters into one, then subset in grass)
- 
-export as ASCII grid
+NextMAP DEMs are supplied in Arc format.  To do the conversion, we use GRASS, though other tools will probably work fine too.   Basic process is:
+ * load in the tiles you need
+ * patch them together, adding zero levels if necessary
+ * output as ASCII
+ * add the azgcorr header line (manually or by script)
 
-[you can load this grid into ENVI to test against vector layers, etc - file->open external->generic->ascii, then georeference (edit headers->mapinfo, etc)]
+----------
+== Command line method ==
+Starting from a valid location (in the correct projection)
 
-The azgcorr format is plain ASCII text, with decimal numbers separated by spaces, one row per row of the DEM.  At the top of the file, you need a single line that describes the geographic position of the DEM.
+{{{
+ # read in a couple of tiles
+r.in.gdal -e input=/data/aegean1/nextmap_dems/neodc/by_tile/by_product/dsm/tl/tl17/tl17dsm/w001001.adf output=tl17
+r.in.gdal -e input=/data/aegean1/nextmap_dems/neodc/by_tile/by_product/dsm/tl/tl17/tl17dsm/w001001.adf output=tl27
+ # set the region of interest to the (two) tiles we want to export
+g.region rast=tl17,tl27
+ # patch them together into a single raster
+r.patch input=tl17,tl27 output=tl17and27
+ # write out as an ASCII DEM (needs editing as below)
+r.out.ascii input=tl17and27 output=/tmp/tl17and27.dem null=0
+}}}
+
+Then run the demheaderconvert.sh script or manually edit the DEM file to include an azgcorr header (or you can specify this on the command line if you prefer).
+
+
+== Adding the azgcorr header ==
 
 Run the script to convert the ASCII file to have an azgcorr compatible header. Note this will delete the original ASCII file unless you specify -nodel at the end. The optional resolution argument specifies the DEM grid resolution in metres, defaults to 5m if omitted.
@@ -42 +54 @@
 Use DEM with azgcorr -eh demfilename
 
-----------
-= Command line method =
-Starting from a valid location (in correct projection?)
-
-{{{
- # read in a tile
-r.in.gdal -e input=/data/aegean1/nextmap_dems/neodc/by_tile/by_product/dsm/tl/tl17/tl17dsm/w001001.adf output=tl17
- # set the region of interest to the (two) tiles we want to export
-g.region rast=tl17,tl27
- # patch them together into a single raster
-r.patch input=tl17,tl27 output=tl17and27
- # write out as an ASCII DEM (needs editing as above)
-r.out.ascii input=tl17and27 output=/tmp/tl17and27.dem null=0
-}}}
-
-(then remember to run the demheaderconvert.sh script).
 
 ---------
-To add a zero-level area to a map (ie sea level):
+== To add a zero-level area to a map (ie sea level): == 
 
 In GRASS: 
@@ -88 +84 @@
 r.out.ascii input=map_with_added_sea_level output=/tmp/map_with_added_sea_level.dem null=0
 }}}
+
+
+== GRASS GUI method ==
+
+(brief description)
+
+load arc files into grass
+ * import->raster->gdal
+ * pick file
+ * choose create new location if this is the first import
+ * run (will fail for UK as it needs user input)
+ * copy and paste command into grass shell so you can respond (e.g. `r.in.gdal -e input=/data/aegean1/nextmap_dems/neodc/by_tile/by_product/dsm/nk/nk02/nk02dsm/w001001.adf output=nk02`
+ * if you need to import multiple rasters, you can use the location created, but must select extend region
+ * (need to figure out how to join rasters into one, then subset in grass)
+ 
+export as ASCII grid, manually add header as above
+
+[you can load this grid into ENVI to test against vector layers, etc - file->open external->generic->ascii, then georeference (edit headers->mapinfo, etc)]