Yeah, I mean the "area of use" as EPSG call it. You can download the EPSG database which contains a table with areas of use from http://www.epsg.org/Geodetic.html and extract that for use in your application if that is going to be helpful for you.
-F On 8 July 2010 16:53, Tomas R <[email protected]> wrote: > You mean > area_of_use_code="2847" > which gives > <Area area_code="2847" area_name="Sweden - 2.5 gon W" area_of_use="Sweden. > For medium and small scale applications:- all country. For large scale > applications:- communes between approximately 14 deg 40 min and 16 deg 55 > min East. See information source for map." > information_source="Lantmateriverket (National Land Survey of Sweden). > http://www.lm.se/geodesi/refsys/rt/rt_projections.html"; data_source="EPSG" > revision_date="2003-06-27" deprecated="0"/> > > > Or is it from this line > <3021> +proj=tmerc +lat_0=0 +lon_0=15.80827777777778 +k=1.000000 > +x_0=1500000 +y_0=0 +ellps=bessel +units=m +no_defs <> > > or from the WKT > PROJCS["RT90 2.5 gon > V",GEOGCS["RT90",DATUM["Rikets_koordinatsystem_1990",SPHEROID["Bessel > 1841",6377397.155,299.1528128,AUTHORITY["EPSG","7004"]],TOWGS84[414.1055246174,41.3265500042,603.0582474221,-0.8551163377,2.1413174055,-7.0227298286,0],AUTHORITY["EPSG","6124"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4124"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",15.80827777777778],PARAMETER["scale_factor",1],PARAMETER["false_easting",1500000],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","3021"]] > > or some other file/source? > All data regarding the Swedish RT90 2.5 V where only the WKT is complete > with toWGS84 parameters. > A not so easy task, and not reliable, to retrieve the info from there I > would guess. > > My goal is not to be 100% accurate at all points in the world, my goal is to > be consistent in the answers to the calls I get. That is the functions > PixelToGPS and GPSToPixel should return "compatible" results at all parts in > the world so that the main application won't have any risk of getting > confused and run into infinite loops or alike. > not to hard to step from (in WGS84) 180 to -180 and +85 to -85 and check for > every fifth degree, or so, if the transformation is valid. When > transformation not valid the plan is to switch to WGS84 which seems to work > even though results can be interesting in the boundary between the > coordinate systems. > > But still, if the info already exists somewhere why not use it but I do not > know if that info exist in the data I have available. > > Thanks anyway > Tomas > > Francis Markham skrev 2010-07-08 08:14: >> >> I think the EPSG dictionary defines areas of validity for the defined >> coordinate systems. That could be a starting point, although there >> may be a better solution >> >> -Francis >> >> On 8 July 2010 16:01, Tomas R<[email protected]> wrote: >>> >>> No one? >>> >>> Ok, I guess then that there are no common function/method of doing this. >>> My >>> approach will the be trial and error. From WGS 84 transform to the local >>> coordinate system and back again to WGS84 and check if the result seems >>> valid. >>> >>> Should work or any expert here have another solution? >>> >>> Yours >>> Tomas >>> >>> Tomas R skrev 2010-07-05 09:05: >>>> >>>> Attacking GDAL via the C# interface and I have a question >>>> >>>> Have set up two (Osr) SpatialReferences and transformations to and form >>>> both. One system is WGS84 and the other is unknown. >>>> >>>> To get a consistent behaviour I need to retrieve the boundary, in WGS84 >>>> coordinates, of the unknown system. If known I can fallback on WGS84 >>>> when >>>> calls outside the scope of the coordinates system are made. >>>> Should be easy to read of some attribute of the SpatialReference or >>>> alike. But which/how? >>>> >>>> Any suggestions? >>>> >>>> Or how should I solve it - in general words: >>>> My application maps coordinates from and to WGS84 and serves them to >>>> another via calls like PixelToGPS and GPSToPixel. The originating >>>> coordinate >>>> system is always WGS84. Need to handle calls made outside the scope of >>>> the >>>> coordinate system and my approach, to get a consisting behaviour of the >>>> two >>>> functions, is to revert to WGS84 which is defined at all possible >>>> points. >>>> >>>> >>>> Yours >>>> Tomas >>> >>> _______________________________________________ >>> gdal-dev mailing list >>> [email protected] >>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>> > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
