Karthik wrote:
Hi,
I have been using GDAL for SDTS raster terrain format
for reading DDF files provided by USGS. To get the exact interpolated
elevation at a particular point, I used the logic in
http://en.wikipedia.org/wiki/Bilinear_interpolation. For verifying
whether the values match exactly, I used Global Mapper but I find that
the variation of around 6 to 10 occurs and some places around 20. I
tried my code on various samples and in almost every sample I get the
same observation. I am sure I am missing something. I am attaching the
CPP file along with the makefile in this mail.
Kart,
I would suggest doing a bit more specific testing.
Do you get an exact match when you check the center of a pixel (ie. no
bilinear interpolation is required?)
I would suspect an off-by-half-pixel error in positioning, but I'm not
brave enough to dig through your code in detail.
Best regards,
--
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