FW: [MetaCRS] RE: Initial commit of CSV Test data files

[Landon Blake]

In the end, you could add something to the comment column of the test
data CSV file that clarified the access order. We made the column names
generic to add that flexibility, correct?

Landon
Office Phone Number: (209) 946-0268
Cell Phone Number: (209) 992-0658
 
 

-----Original Message-----
From: metacrs-bounces at lists.osgeo.org
[mailto:metacrs-bounces at lists.osgeo.org] On Behalf Of Frank Warmerdam
Sent: Monday, November 30, 2009 11:48 AM
To: Norm Olsen
Cc: metacrs at lists.osgeo.org
Subject: Re: [MetaCRS] RE: Initial commit of CSV Test data files

Norm Olsen wrote:
> Interesting point.  EPSG does specify latitude, longitude, and then
height.  My experience says that many (if not most) coordinate system
libraries use the longitude, latitude, height convention.  That is,
99.8% of the time and regardless of whether the coordinate system is
projective or geographic, the first ordinate increases to the east, the
second ordinate increases to the north, and the third ordinate increases
away from the center of the earth.  I don't know what the default
preference for Proj4 is, so I'd be interested in knowing of the opinions
of the Proj4 folk on this.
> 
> Dogmatically, EPSG is correct.  Pragmatically, I believe longitude,
latitude, and then height is correct. 

Norm,

PROJ.4 is still "axis orientation ignorant" so it does indeed assume
long, lat, height for geographic coordinates.  However, the GDAL
OGRSpatialReference and OGRCoordinateTransformation classes try to have
some sort of knowledge of SRS axis ordering though this work is not
really
complete at this time.

While I hate the misery that the epsg lat/long axis police have caused
in this world (mostly via more recent OGC specifications) I am not sure
ignoring the EPSG axis definitions is the right thing to do.  I've got
a foot on either side of this issue and so I've tried not to take a
position.

In part I suppose it depends on whether our objective is for the test
data to address broadly defined coordinate system transformations as
opposed to being primarily focused on projection transformations.  If
the former then we ought to expect test apps to honour the axis
definitions
of the coordinate system. If the latter then sticking to a default axis
orientation (perhaps only for geographic coordinates) would be fine.

I can go either way.

Best regards,
-- 
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------
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    | Geospatial Programmer for Rent

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