[Proj] Re: another approach

Frank Warmerdam warmerdam at pobox.com
Thu Mar 1 09:50:30 EST 2007

Sergey Spiridonov wrote:
> Hash: SHA1
> Hi,
> Another approach I can think of is having set of key points (let's say
> 5-20) on the Earth (lat,lon), which will be projected in both
> projections which are compared. Than the resulting map coordinates can
> be compared. If projections are the same, map coordinates of the
> projected points will be also the same. If projections differ, thanwell,
> map coordinates should be also different? (if set is good enough?)
> What do you think about this?


As long as you can ensure that the sample points are in the domain of validity
of the coordinate system, and that they are representative (ie. well dispersed)
then this would be good.  But even knowing the domain of a coordinate system
is hard to do systematically (ie. without apriori knowledge about the
coordinate system).  This is especially true when using coordinate systems
with datum shift files that only apply to particular regions.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org

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