[gdal-dev] C GDAL beginner

deadpickle deadpickle at gmail.com
Tue Mar 2 22:22:58 EST 2010

I'm trying to write a simple C program that creates and populates a
shapefile (have one done in python). I'm very new to C and GDAL both
and could use some help. I'm trying to apply coordinatetransformation
to my points but first I have to create the coordinatetransformation.
In python I can do this simply by:
coordtrans = osr.CoordinateTransformation(target, source)
but in C I cant seem to find the right call for this. Any ideas?

#include "ogr_api.h"
#include "ogr_srs_api.h"

int main()
	//~ variable declaration
	const char *format = "ESRI Shapefile", *name = "testc.shp", *source,
	const char *sprj = "+proj=lcc +lat_1=33.000000 +lat_2=45.000000
+lat_0=39.000000 +lon_0=-96.000000 +x_0=0.0 +y_0=0.0 +datum=NAD83";
	const char *tprj = "WGS84";
	OGRSFDriverH driver;
	OGRDataSourceH ds;
	OGRCoordinateTransformation ctrans;

	//~ get driver and create ds
	driver = OGRGetDriverByName(format);
	ds = OGR_Dr_CreateDataSource(driver, "testc.shp", NULL);

	//~ create spatrefs and trans
	OSRSetFromUserInput(source, sprj);
	OSRSetFromUserInput(target, tprj);
	ctrans = OGRCreateCoordinateTransformation(target, source);

[thor at updraft ~/Programs]$ gcc -o gdal_test_convert
gdal_test_convert.c: In function ‘main’:
gdal_test_convert.c:12: error: ‘OGRCoordinateTransformation’
undeclared (first use in this function)
gdal_test_convert.c:12: error: (Each undeclared identifier is reported
only once
gdal_test_convert.c:12: error: for each function it appears in.)
gdal_test_convert.c:12: error: expected ‘;’ before ‘ctrans’
gdal_test_convert.c:22: warning: passing argument 1 of â
€˜OSRSetFromUserInput’ discards qualifiers from pointer target type
gdal_test_convert.c:23: warning: passing argument 1 of â
€˜OSRSetFromUserInput’ discards qualifiers from pointer target type
gdal_test_convert.c:24: error: ‘ctrans’ undeclared (first use in
this function)

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