At 05:16 PM 8/28/2001 -0400, Bill Huber wrote:
>If your dataset has relatively small extent, you could consider
>approximating the full change of coordinates. There are many
>techniques. A general-purpose technique that is easy to implement and
>fast in computation consists of developing a regular rectangular grid of
>transformed values (using your GIS of course) and then performing bilinear
>interpolation within the grid to estimate the transformed values at other
>points.
[ ... trimmed ...]
>Another approach is to fit a polynomial or rational function to a
>collection of known transformed values. Use multiple linear regression to
>find the coefficients. There is more up-front work in doing the
>regression analysis, but implementing a rational function in code is easy
>and easily tested. The actual computations will be pretty fast.
Wow, Bill, you've really sparked my interest with this. I'm imagining a way
of reprojecting data on the fly for display purposes. I would use the above
methodology to convert from Lat Long to Lambert Conformal ( or whatever )
to pixel in one swoop. The number of points in the transfer function would
be determined by the pixel size of the requested image. Too cool.
Can you point me to any info on how to do either of the above algorithms?
I'm sure they are described in greater detail somewhere.
Thanks,
Marc Pelletier
Traxis Inc.
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