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On Sun, 2005-08-07 at 18:02 +0200, Patrick Mézard wrote:<BR>
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<FONT COLOR="#000000">I suppose I can ignore the False Easting and Northing. Latitude and </FONT>
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Yes, indeed
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<FONT COLOR="#000000">longitude of natural origin would be the projection center point. </FONT>
<FONT COLOR="#000000">Remains the scale factor. I could let it at 1.0. But maybe there is a </FONT>
<FONT COLOR="#000000">way to generate it programmatically given a center point, and ellipsoid </FONT>
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Assuming that most of the points are within so many meters (ie. 50m) of the central point<BR>
(lat_0, lon_0) then select a k_0 factor that would make the scale factor 1<BR>
half way between the center point and projection limit. The center's true scale will be<BR>
somewhat larger than 1. and the rim slightly smaller. Start with about +k_0=.99999 .<BR>
Use the -V option to experiment.<BR>
<BR>
If you are keeping within 50km. scale errors should probably kept to within much better than 1 part in<BR>
100000 or close to your 2/3 meter.
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<FONT COLOR="#000000">and a working area radius. It probably does not worth the pain however. </FONT>
<FONT COLOR="#000000">Are the output coordinate units naturally in meters or have I missed </FONT>
<FONT COLOR="#000000">other parameters ?</FONT>
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The Cartesian coordinates are the same as the ellipsoid major axis units. If 'a' is in<BR>
meters then the x-y values are in meters. There is also a scaling parameter.<BR>
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--
_____________________________________________________________
Jerry and the Low Riders: Daisy Mae and Joshua
"The most certain test by which we judge whether a country is
really free is the amount of security enjoyed by minorities"
---Lord Acton, 1907
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