[gdal-dev] gdaldem slope with -s 111120.0 works only at equator for lat/lon?
jea at hbaspecto.com
Fri Jan 24 15:47:45 PST 2014
Here’s a diff on the .dox for gdaldem, as a suggestion. (I don’t want commit access on the repository. Is sending the diff by email the appropriate approach?)
Note I’m assuming that the other modules in gdaldem also assume that x and y units are the same.
--- gdal_utilities.dox (revision 26875)
+++ gdal_utilities.dox (working copy)
@@ -2038,8 +2038,14 @@
[-compute_edges] [-b Band (default=1)] [-of format] [-q]
- Scale is the ratio of vertical units to horizontal
- for Feet:Latlong use scale=370400, for Meters:LatLong use scale=111120)
+ gdaldem generally assumes that x, y and z units are identical. If x (east-west)
+ and y (north-south) units are identical, but z (elevation) units are different, the
+ scale (-s) option can be used to set the ratio of vertical units to horizontal. For
+ LatLong projections near the equator, where units of latitude and units of
+ longitude are similar, elevation (z) units can be converted to be compatible
+ by using scale=370400 (if elevation is in feet) or scale=111120 (if elevation is in
+ meters). For locations not near the equator, it would be best to reproject your
+ grid using gdalwarp before using gdaldem.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the gdal-dev