[gdal-dev] Converting raster pixel space to geospace

[Martin Chapman]

Gary,

 

Set your paths like such on startup or as an environment variable:

 

GDAL_DATA points at the data dir that comes with gdal source.

PROJ_LIB point to the nad directory that you download from proj4 website.

 

string env = string("GDAL_DATA=") + dataPath;

_putenv(env.c_str());

env = string("PROJ_LIB=") + nadPath;

_putenv(env.c_str());

 

and / or

 

CPLSetConfigOption("GDAL_DATA", dataPath.c_str());

CPLSetConfigOption("PROJ_LIB", nadPath.c_str());

 

Martin

 

From: gdal-dev-bounces at lists.osgeo.org
[mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Smart, Gary
Sent: Monday, July 20, 2009 7:38 AM
To: gdal-dev at lists.osgeo.org
Subject: RE: [gdal-dev] Converting raster pixel space to geospace

 

 

 

OK - I can get it to compile and not crash instantly (bonanza!)

 

However, when I try to create the OGR transform using importFromWkt, 

I get the following:

 

ERROR 6: Unable to load PROJ.4 library (libproj.so), creation of

OGRCoordinateTransformation failed.

 

Does anyone know what this means?  Is there some part of OGR/GDAL I have yet
to install?

 

My input projection is:

GTiff/GeoTIFF Projection PROJCS["TM
D-01",GEOGCS["NAD27",DATUM["North_American_Datum_1927",SPHEROID["Clarke
1866",6378206.4,294.9786982139006,AUTHORITY["EPSG","7008"]],AUTHORITY["EPSG"
,"6267"]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433],AUTHORITY[
"EPSG","4267"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_ori
gin",0],PARAMETER["central_meridian",-124.5],PARAMETER["scale_factor",1],PAR
AMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["metre",1,AUTHO
RITY["EPSG","9001"]]]

 

...and I am looking to output WGS84 lat/longs.

 

 

> -----Original Message-----

> From: Even Rouault [mailto:even.rouault at mines-paris.org]

> Sent: 16 July 2009 19:44

> To: Smart, Gary

> Cc: gdal-dev at lists.osgeo.org

> Subject: Re: [gdal-dev] Converting raster pixel space to geospace

> 

> Le Thursday 16 July 2009 10:41:02 Smart, Gary, vous avez écrit :

> >

> > But how do I load a OGRSpatialRef object with the output from the

> > GDALApplyGeoTransform?  Presumably I can prime the OGRSpatialReference

> > using the result of GDALDataset::GetProjectionRef?

> 

> Yes, almost. See below

> 

> > I'm not yet sure of my

> > terminology but is the GetProjectionRef supposed to satisfy the OGR

> > importFromWkt (the types seem to clash though - char* vs char**)?

> 

> Maybe the doc of OGRSpatialReference::importFromWkt() (see

> http://gdal.org/ogr/classOGRSpatialReference.html#b74cfc985bd05404a4c61d2d

> 633a6343)

> isn't clear enough ? I must confess that the prototype is a bit weird. You

> don't pass the string itself, but a pointer to a string. The pointer will

> be

> modified to point to the remaining (unused) input, what you generally

> don't

> care about.

> 

> Ok, here's a sample snippet :

> 

> OGRSpatialReferenceH hSRS = OSRNewSpatialReference(NULL);

> const char* pszWkt = GDALGetProjectionRef(hDS);

> OSRImportFromWkt(hSRS, (char**) pszWkt);

> 

> (For the purists, a more correct prototype of importFromWkt () would have

> relied on 'const char**' to avoid the above cast)

> 

> But a simpler approach would be just :

> 

> OGRSpatialReferenceH hSRS;

> hSRS = OSRNewSpatialReference(pszWKT);

> 

> which instanciates the OGRSpatialReferenceH object and call internally

> importFromWkt()

> 

> >

> > I suspect my output projection could then be set up with

> > SetWellKnownGeogCS("WGS84") in order to convert from whatever input

> > projection prevails, to a standard WGS84 lat/long representation (using

> >    OGRCreateCoordinateTransformation::Transform)?

> 

> Yes. Actually, it will be long/lat in term of the order of the

> coordinates.

> 

 

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