[gdal-dev] Transformation methods & parameters (OGRCoordinateTransformation)

[César Martínez]

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

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