Michael Perdue wrote:
Ops... Looks like Geotiff does allow for storing no-data values. But HFA (not too sure which format IMA is) and others don't appear too.
Michael, Note that GeoTIFF does not *generally* support nodata values, but there is a GDAL specific tag used by GDAL and GDAL based software to keep track of nodata values.
Question? is float(nan) equal to double(nan)?
They are not the same as the binary level of course. I don't know if they compare as equal in C or not. Hopefully they do. However, GDAL does *not* generally recognise NaN as a nodata value. > If not, does gdal_translate
understand this when it converts a file stored as float64 to float32? gdal_translate allows one to define what the no-data value is, but how do I tell it to change the input no-data value to a different output no-data value? IE, the no-data value in my surfer file is a double precision nan, but I want the no-data value in my output GeoTiff (float32) to be -32767. -a_nodata changes the header no-data definition but does not change the values of the pixels that represent no-data.
I'm not aware of a practical way of doing this. Sorry. You are likely best off fixing this up in GRASS which is more flexible. (BTW, GDAL does support double precision geotiff files) Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | President OSGeo, http://osgeo.org _______________________________________________ grassuser mailing list [email protected] http://grass.itc.it/mailman/listinfo/grassuser
