Python trig precision problem
Robert Kern
robert.kern at gmail.com
Fri May 19 00:21:42 EDT 2006
Cary West wrote:
> Hello all, having a small problem with a trig routine using python math
> module. This code is designed to convert geodetic coordinates to lambert
> conformal conic coordinates. It implements the formulas found at
> http://mathworld.wolfram.com/LambertConformalConicProjection.html . The
> problem is that, at least on my machine, the precision is off to the tune of
> around 1 km, which is unacceptable. (using the calculator found at
> http://www.deh.gov.au/erin/tools/geo2lam-gda.html ) Anyone have any ideas?
> here is the offending code.
If you want to do map projections, I highly recommend using PyProj instead of
implementing the calculations yourself. Geodesy is nontrivial, and MathWorld
doesn't tell you half the details you need to take care of.
http://www.cdc.noaa.gov/people/jeffrey.s.whitaker/python/pyproj.html
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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