[josm-dev] WMTS scales - proper definition of 1m along meridian

Paul Hartmann phaaurlt at gmail.com
Mon Jul 6 21:13:44 UTC 2015


On 06.07.2015 21:15, Wiktor Niesiobedzki wrote:
> 2015-07-06 10:54 GMT+02:00 Paul Hartmann <phaaurlt at gmail.com>:
>> Strange... It would be interesting to see how other projects are handling
>> this, e.g. QGIS and GDAL.
>
> This is good hint. I've checked QGIS, but it actually uses GDAL
> definitions. And GDAL has following information:
>
> """"
> AXIS
> The name of the axis is for human consumption. The enumerated value
> that follows is to allow software to correctly overlay different
> coordinate systems. If the optional AXIS terms are not present, then
> the default values are assumed. They are:
> Geographic Coordinate System(GEOGCS) - AXIS["Lon",EAST],AXIS["Lat",NORTH]
> Projected Coordinate System(PROJCS) - AXIS["X",EAST],AXIS["Y",NORTH]
> """"
> (http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html)
>
>
> So all GCS-es are North, East and need switch.

I don't get this from the above quote, but it may well be true.

> When I check WKT for
> 4326 and 2180 I see:
> PROJCS["ETRS89 / Poland
> CS92",GEOGCS["ETRS89",DATUM["European_Terrestrial_Reference_System_1989",SPHEROID["GRS
> 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6258"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4258"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",19],PARAMETER["scale_factor",0.9993],PARAMETER["false_easting",500000],PARAMETER["false_northing",-5300000],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","2180"]]
>
> GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS
> 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]

No axes info in these WKT strings, so basically the same as in the epsg 
file...

> So it looks like, for EPGS:4326 this default works, but not for 2180.
> Strange. I didn't have had occasion to test, if it works properly in
> QGIS in WMTS or WMS 1.3.0.
>
> So I guess I'll have to go trough epsg registry for all our
> projections and add +axis= parameter. I do not see any way, to induce,
> whether we are working with PROJCS or GEOGCS.

You can download the EPSG file and sort of automate this:
$ echo 'select COORD_SYS_CODE from "Coordinate Reference System" where 
COORD_REF_SYS_CODE=2180' | mdb-sql -pHF EPSG_v8_7.mdb
 > 4531
$ echo 'select COORD_SYS_TYPE,COORD_SYS_NAME from "Coordinate System" 
where COORD_SYS_CODE=4531' | mdb-sql -pHF EPSG_v8_7.mdb
 > Cartesian  Cartesian 2D CS. Axes: northing, easting (x,y). 
Orientations: north, east. UoM: m.

Best, Paul





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