General GDAL Operations

Functions
GDALDatasetH	openRasterDataset (const char *filePath)
	Open a raster dataset in read-only mode.
GDALRasterBandH	openRasterBand (GDALDatasetH raster, int index)
	Fetch a raster band from an opened raster dataset.
GDALDatasetH	openVectorDataset (const char *filePath)
	Open a vector dataset in read-only mode.
OGRLayerH	openVectorLayer (GDALDatasetH vector, const char *name)
	Fetch a vector layer from an opened vector dataset.
void	closeGDALDataset (GDALDatasetH dataset)
	Close an open raster or vector dataset.
CRS_TYPE	getCRSType (const char *Wkt)
	Determine if a given CRS is geographic or planar/projected.
char *	extractCRSAsWKT (GDALDatasetH dataset, const char *layerName)
	Return the dataset/layer CRS as WKT.
OGRCoordinateTransformationH	transformationFromWKTs (char *from, char *to, bool inputUsesCompliantOrdering)
	Create a coordinate transformation between to CRS's.
GEOSGeometry *	OGRToGEOS (const OGRGeometryH geom)
	Convert an OGR geometry to a GEOS geometry.
OGRGeometryH	OGRFromGEOS (const GEOSGeometry *geom, OGRSpatialReferenceH crs)
	Convert a GEOS geometry to an OGR geometry.

Detailed Description

Function Documentation

closeGDALDataset()

void closeGDALDataset

(

GDALDatasetH

dataset

)

Close an open raster or vector dataset.

Note

This function may call exit(1) if closing the GDALDatasetH object failed.

Parameters

dataset

Object to close.

extractCRSAsWKT()

char * extractCRSAsWKT ( GDALDatasetH dataset, const char * layerName )

nodiscard

Return the dataset/layer CRS as WKT.

This function works on raster and vector datasets. It extracts the the projection of the dataset and returns a new reference to its WKT representation.

Note

After the function returns, the caller owns the returned char * object and must free/destroy it after use with CPLFree.

Parameters

dataset	GDAL dataset object to query for CRS infromation.
layerName	Layer name to query. Only honored for vector datasets.

Returns

char* Pointer to WKT string, NULL on error

getCRSType()

CRS_TYPE getCRSType

(

const char *

Wkt

)

Determine if a given CRS is geographic or planar/projected.

Note

If CRS type couldn't be fetched, CRS_UNKNOWN is returned indicating an error.

Parameters

Wkt	String representation of CRS.

Returns

CRS_TYPE Type of CRS.

OGRFromGEOS()

OGRGeometryH OGRFromGEOS ( const GEOSGeometry * geom, OGRSpatialReferenceH crs )

nodiscard

Convert a GEOS geometry to an OGR geometry.

This function creates a temporary GEOS WKB-writer and converts the input GEOS geometry to a corresponding OGR geometry by ex-/importing via the respective WKB interfaces.

Note

After the function returns, the caller owns the returned OGRGeometryH object and must free/destroy it after use.

Warning

This function is not reentrant or thread-safe!

Parameters

geom	GEOS geometry to convert.
crs	Spatial reference object to assign to geometry, can be NULL.

Returns

OGRGeometryH Converted geometry, NULL on error.

OGRToGEOS()

GEOSGeometry * OGRToGEOS ( const OGRGeometryH geom )

nodiscard

Convert an OGR geometry to a GEOS geometry.

This function creates a temporary GEOS WKB-reader and converts the input OGR geometry to a corresponding GEOS geometry by ex-/importing via the WKB interfaces.

Note

The C++-API of GDAL offers a direct interface to export OGR geometries to GEOS. Since GDAL's C-API does not offer such functionality, this workaround is needed.

After the function returns, the caller owns the returned GEOSGeometry object and must free/destroy it after use.

Warning

This function is not reentrant or thread-safe!

Parameters

geom	OGR geometry to convert.

Returns

GEOSGeometry* Converted geometry, NULL on error.

openRasterBand()

GDALRasterBandH openRasterBand	(	GDALDatasetH	raster,
		int	index )

Fetch a raster band from an opened raster dataset.

Note

The raster band indices are 1-based.

Remarks

The returned raster band is owned by the corresponding raster dataset and should not be freed/destroyed.

Parameters

raster	Raster object to fetch band from.
index	Band index.

Returns

GDALRasterBandH GDAL handle to raster band, NULL on failure.

openRasterDataset()

GDALDatasetH openRasterDataset ( const char * filePath )

nodiscard

Open a raster dataset in read-only mode.

Remarks

After the function returns, the caller owns the returned GDALDatasetH object and must close it after use.

Parameters

filePath

Raster file to open.

Returns

GDALDatasetH GDAL handle to opened dataset, NULL on failure.

openVectorDataset()

GDALDatasetH openVectorDataset ( const char * filePath )

nodiscard

Open a vector dataset in read-only mode.

Warning

The GML and GMLLAS drivers are dregistered because it's explicitly mentioned they maybe not import coordinates in a "gis friendly" way!

Remarks

After the function returns, the caller owns the returned GDALDatasetH object and must close it after use.

Parameters

filePath

Vector file to open.

Returns

GDALDatasetH GDAL handle to opened dataset, NULL on failure.

openVectorLayer()

OGRLayerH openVectorLayer	(	GDALDatasetH	vector,
		const char *	name )

Fetch a vector layer from an opened vector dataset.

Note

If name is null, the first vector layer is returned.

Remarks

The returned vector layer is owned by the corresponding vector dataset and should not be freed/destroyed.

Parameters

vector	Vector object to fetch layer from.
name	Layer name to fetch, possibly NULL.

Returns

OGRLayerH GDAL handle to vector layer, NULL on failure.

transformationFromWKTs()

OGRCoordinateTransformationH transformationFromWKTs	(	char *	from,
		char *	to,
		bool	inputUsesCompliantOrdering )

Create a coordinate transformation between to CRS's.

This function creates OGRSpatialReferenceH objects from the supplied WKT representations. The transformation object is created using the OCTNewCoordinateTransformationEx function, setting optional arguments to NULL. The returned coordinate transformation object can be used with various transformation API's offered by GDAL.

Remarks

The returned object is owned by the caller and must be freed/destroyed after use.

Parameters

from	Source CRS as WKT string.
to	Destination CRS as WKT string.
inputUsesCompliantOrdering	Boolean flag indicating if the CRS associated with the object to transform uses authority compliant ordering or gis friendly ordering. When data is read from file, this is most likely false.

Returns

OGRCoordinateTransformationH A new transformation object, NULL on error.