[MetaCRS] Non-Programming Collaboration

[Frank Warmerdam]

Landon Blake wrote:
> I'm glad that I did not step on your toes. :]
> 
> I've also added an item for developer articles.
> 
> I think that "Common Spatial Reference System or Coordinate Reference
> System Names and Descriptions" and " Coordinate System (and CRS related
> object) dictionaries. Stuff like the EPSG dictionary" might be the same
> thing. Maybe I should delete the first one to avoid confusion?

Landon,

I think they are closely related but not necessarily the same thing.

> How would we have a test suite that was not specific to a programming
> language?

I'm imagining a CSV file with the following columns:

Projected Coordinate System ID: (possibly WKT or an EPSG id)
proj_easting
proj_northing
proj_z
same_datum_longitude
same_datum_latitude
same_datum_z
wgs84_longitude
wgs84_latitude
wgs84_z

Then a test run could use a particular engine, transform the point from
projected to lat/long (on the same datum), check, and then back to
projected coordinates and check again.

The test could also transform to WGS84 and back checking at both ends.

Some sort of tolerance might also be appropriate in the test records.

As long as is a common way of describing coordinate systems we should
be in good shape.  I am hopefully that OGC WKT could be a common
exchange format for the different systems.  If nothing else, we should
at least all support EPSG's dictionary.

> P.S. - I'm going to dig around for information about a pseudo code
> standard. It would be nice if we could describe transformations,
> calculations, and algorithms in a standard pseudo code. I could start us
> off with some pseudo code for California State Plane Coordinates, since
> I've become way more familiar with the system than any man should as a
> result of studying for my licensed surveyor exam. :]

I'm not sure how critical this is.  State plane coordinate systems are
based on a few fairly well known projection methods with parameters
available in the EPSG dictionary (as well as elsewhere).   There are already
algorithm descriptions for a variety of projection methods from various
places.  One of them is the EPSG dictionary itself.

BTW, I have in the past (poorly) maintained the following pages which
I hope will become part of the MetaCRS project and better maintained.

   http://geotiff.maptools.org/proj_list

They attempt to describe the projection methods, and relate them back
to EPSG codes, and various other coordinate system formats.

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