[MetaCRS] Standard (and simple) format for conversion tests.

[Martin Desruisseaux]

Landon Blake a écrit :
> Martin D wrote: " Maybe the tolerance should be specified for each axis, instead than one value applying to all axis. This is more useful when the target CRS is a geographic one, since the tolerance on longitude can become greater as we approach the pole. At the extreme case (point a North pole or South pole), the longitude is meanless and should have a tolerance of +/- 180"
> 
> Now that I think about it, why have the tolerances specified in the test data files at all? Let the programmer writing the tests that will use the files set his own tolerance values and determine which tolerance is most important to him/her.

Suggesting a tolerance can make the job easier for the tester (one less thing to 
think about), especially since the tolerance depends on the unit of measurement, 
the proximity of pole in case of geographic CRS, whatever the operation involve 
a datum shift or not (to phrase that in ISO 19111 terms: whatever the operation 
is a "conversion" or a "transformation"), etc. However I'm fine with either 
approach (including or excluding them from the test file).


> Martin D wrote:" Maybe the axis order should be "as the authority said" (useful for testing libraries to be used with recent WMS/WCS versions), instead than forced to "X Y Z" order. As a help for libraries that do not handle axis ordering, we could add a field telling what the order is for the current record."
> 
> Good point. So maybe we do something like this:
> 
> X:60321125.25 Y:2335688.21 Z:12.20

If we define "X" and "Y" as "first and second axis in a right-handed system", 
I'm fine. We can not said "X=Easthing and Y=Northing" (except informaly) because 
it doesn't work at poles (e.g. Polar Stereographic projections), while a 
right-handed system is well defined everywhere.

	Martin