Hi Stuart-
Stuart Maclean wrote:
I am not sure of the correct home for the ucar.unidata.geoloc.*
package, is it IDV, Netcdf, or some other jar?
The IDV and netCDF Java share some common code and now that
package is part of the netCDF-Java source.
Anyway, in idv 2.2 there exists
ucar.unidata.geoloc.projection.LambertConformal. I am
copying/transcribing this class into a GWT (Java -> Javascript)
class. I note this snippet in the projToLatLon method:
double yd = (rhop - fromY); double theta = Math.atan2(fromX, yd);
double r = Math.sqrt(fromX * fromX + yd * yd); if (n < 0.0) {
In the call to Math.atan2, we clearly have some x distance as first
parameter, with y second.
Yet the api for java.lang.Math.atan2 suggests that the parameter
order is y, x. Can anyone explain why the apparent mismatch? I have
used this class in apps before and it seems to work fine.
See:
http://mathworld.wolfram.com/LambertConformalConicProjection.html
for an explanation of the algorithm. In particular, this
is from:
theta = tan^(-1)(x/(rho_0-y))
which ends up as atan(x,y)
Don
*************************************************************
Don Murray UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000
(303) 497-8628 Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
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