Hi, we are evaluating using Gdal/OGR in order to manage CRSs and transformations on a project. I have read the OGR Projections Tutorial [1] and also had a look to the OGRSpatialReference & OGRCoordinateTransformation API.
However, I have not found a simple way to get a list of available transformation operations between 2 specific CRSs, or at least to guess which transformation method and parameters is being used by a particular OGRCoordinateTransformation instance. This is relevant because sometimes there are several transformation operations available between 2 CRSs, and we'd like our users being able to choose which operation they'd like to use. For instance, between EPSG:23030 and EPSG:4326, at least the following transformations are suitable for Spain: EPSG:15933, EPSG:1633, EPSG:1133, EPSG:1145 [2], each using different methods & parameters and thus providing different accuracy. Is there a simple way to get this information? In case this is not possible and we get this information from a separate source (e.g. the official EPSG database), which is the best way to instantiate a particular transformation method in GDAL? I believe it is possible by using some proj4 parameters when creating the OGRSpatialReference. Is there any alternative way (such as directly specifying the transformation method & parameters to the OGRCoordinateTransformation constructor)? Thanks in advance, César Martínez Izquierdo [1] http://www.gdal.org/osr_tutorial.html [2] See http://epsg.io/15933 http://epsg.io/1633 http://epsg.io/1133 http://epsg.io/1145 -- SCOLAB http://scolab.es _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
