GDAL should not be converting NaNs to anything, just passing
them through as-is.
And that is what currently happens if the data is requested as a float.
Actually, I am reading float32 and asking for float32, and yet the NaNs
are converted to 0.
Well, there is work, and there is work. GDAL has a nodata scheme tuned
to integer data where the "nodata value" is kept track of as a special
sort of metadata.
Aha! I did not know about this option. I will investigate further.
Unfortunately, it does not seem that the software I use to generate
these TIFFs (IDL) will let me insert the GDAL_NODATA tag (#42113, I
gather) when I write the file.
I would claim you produced a poor product by not providing the metadata
indicating that NaN should be treated as nodata.
If there is a way for me to provide such metadata about NaN, I will do it.
There are many different pieces of logic things can go through
in MapServer WCS. For instance IMAGEMODE BYTE is handled quite
distinctly from IMAGEMODE RGB or IMAGEMODE PC256. It can make
quite a difference whether you are going through reprojection or not.
Some of these code paths do not support "nodata" value because the
imagery is scaled to 8bit before any operations that could recognise
nodata.
I am using IMAGEMODE "FLOAT32" in my OUTPUTFORMAT declaration. Does that help?
Thanks,
Jeff DLB
