<div class="gmail_quote">On Thu, Sep 29, 2011 at 7:21 PM, <span dir="ltr"><<a href="mailto:Tony.Na@sybase.com">Tony.Na@sybase.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br>
Hi fellow GDAL/OGR developers,<br>
I'm currently developing an OGR data provider module for Sybase SQLAnywhere<br>
database, which recently supports spatial features in it's version 12<br>
release. I have a question regarding the best way to evaluate the<br>
equivalence between two Spatial Reference Systems. It seems to me that<br>
when I use ogr2ogr to translate a SQLAnywhere Layer to a shapefile, the<br>
shapefile data provider calls the morphToESRI() and morphFromESRI<br>
functions, which strips out all Authority nodes from my original SRS WKT.<br>
For example, for the SRS “NAD27 / Alaska Albers”, the WKT representation<br>
before and after the morph follows:<br>
<br>
<br>
Before morph:<br>
<br>
<br>
PROJCS["Albers Equal Area",<br>
GEOGCS["NAD27",<br>
DATUM["North_American_Datum_1927",<br>
SPHEROID["Clarke 1866", 6378206.4, 294.978698213898,<br>
AUTHORITY["EPSG","7008"]],<br>
TOWGS84[-3,142,183,0,0,0,0],<br>
AUTHORITY["EPSG","6267"]],<br>
PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],<br>
UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],<br>
AUTHORITY["EPSG","4267"]],<br>
PROJECTION["Albers_Conic_Equal_Area"],<br>
PARAMETER["standard_parallel_1",55],<br>
PARAMETER["standard_parallel_2",65],<br>
PARAMETER["latitude_of_center",50],<br>
PARAMETER["longitude_of_center",-154],<br>
PARAMETER["false_easting",0],<br>
PARAMETER["false_northing",0],<br>
UNIT["us_survey_feet",0.3048006096012192],<br>
AUTHORITY["EPSG","2964"]]<br>
<br>
After morph:<br>
PROJCS["Albers_Equal_Area",<br>
GEOGCS["GCS_North_American_1927",<br>
DATUM["D_North_American_1927",<br>
SPHEROID["Clarke_1866",6378206.4,294.9786982]],<br>
PRIMEM["Greenwich",0],<br>
UNIT["Degree",0.017453292519943295]],<br>
PROJECTION["Albers"],<br>
PARAMETER["standard_parallel_1",55],<br>
PARAMETER["standard_parallel_2",65],<br>
PARAMETER["latitude_of_origin",50],<br>
PARAMETER["central_meridian",-154],<br>
PARAMETER["false_easting",0],<br>
PARAMETER["false_northing",0]<br>
,UNIT["Foot_US",0.30480060960121924]]<br></blockquote><div><br></div><div><a href="http://prj2epsg.org">prj2epsg.org</a> is able to tell you that the above is EPSG:2964, try it out.</div><div>It is however based on the GeoTools referencing subsytem, not OGR</div>
<div><br></div><div>Cheers</div><div>Andrea</div><div> </div></div><div><br></div>-- <br>-------------------------------------------------------<br>Ing. Andrea Aime<br>GeoSolutions S.A.S.<br>Tech lead<br><br>Via Poggio alle Viti 1187<br>
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