systematic

Functions
OGRGeometry *	sgs::systematic::getAccessPolygon (vector::GDALVectorWrapper *p_access, std::string layerName, double buffInner, double buffOuter)
bool	sgs::systematic::checkExtent (double x, double y, double xMin, double xMax, double yMin, double yMax)
bool	sgs::systematic::checkAccess (OGRPoint *p_point, OGRGeometry *p_geometry)
bool	sgs::systematic::checkExisting (double x, double y, existing::Existing &existing)
bool	sgs::systematic::checkNotNan (raster::GDALRasterWrapper *p_raster, double *IGT, double xCoord, double yCoord, bool force)
std::tuple< vector::GDALVectorWrapper *, std::vector< std::vector< double > >, std::vector< std::vector< std::vector< double > > > >	sgs::systematic::systematic (raster::GDALRasterWrapper *p_raster, double cellSize, std::string shape, std::string location, vector::GDALVectorWrapper *p_existing, vector::GDALVectorWrapper *p_access, std::string layerName, double buffInner, double buffOuter, bool force, bool plot, std::string filename)

Detailed Description

Function Documentation

checkAccess()

bool sgs::systematic::checkAccess ( OGRPoint * p_point, OGRGeometry * p_geometry )

inline

Helper function for checking to see whether a pixel occurs within accessible area.

Parameters

OGRPoint	*p_point
OGRGeometry	*p_geometry

Returns

bool

checkExisting()

bool sgs::systematic::checkExisting ( double x, double y, existing::Existing & existing )

inline

Helper function for checking to see whether a pixel is already an existing sample location.

Parameters

double	x
double	y
Existing&	existing

Returns

bool

checkExtent()

bool sgs::systematic::checkExtent ( double x, double y, double xMin, double xMax, double yMin, double yMax )

inline

Helper function for ensuring the x and y coordinates are within the raster extent.

Parameters

double	x
double	y
double	xMin
double	xMax
double	yMin
double	yMax

Returns

bool

checkNotNan()

bool sgs::systematic::checkNotNan ( raster::GDALRasterWrapper * p_raster, double * IGT, double xCoord, double yCoord, bool force )

inline

Helper function for checking to see whether a coordinate occurs in an area of nodata.

the 'force' parameter is first checked, because if force is not true, then samples are allowed to occur on nodata pixels.

THe inverted geotransform is used to find the x and y values from the coordinates given. Then, every raster band within the input raster is checked, and if that pixel is a no data value in any of them false is returned. the GDALRasterBand RasterIO function is used to read the desried pixel from the raster.

Parameters

GDALRasterWrapper	*p_raster,
double	*IGT
double	xCoord
double	yCoord
bool	force

Returns

bool

getAccessPolygon()

OGRGeometry * sgs::systematic::getAccessPolygon	(	vector::GDALVectorWrapper *	p_access,
		std::string	layerName,
		double	buffInner,
		double	buffOuter )

Helper function for generating a vector geometry containing polygons of the accessible area. This function is called if an access vector is given.

The input vector dataset must be comprised of solely LineString and MultiLineString geometries. The LineStrings are buffered by buff outer, then have buff_inner subtracted from them.

The returned geometry is checked to see whether it contains points which are trying to be sampled. If the geometry does not contain a given point, that point is considered inaccessible and thus not sampled.

Parameters

GDALVectorWrapper	*p_access
std::string	layerName
double	buffInner
double	buffOuter

Returns

OGRGeometry *

systematic()

std::tuple< vector::GDALVectorWrapper *, std::vector< std::vector< double > >, std::vector< std::vector< std::vector< double > > > > sgs::systematic::systematic	(	raster::GDALRasterWrapper *	p_raster,
		double	cellSize,
		std::string	shape,
		std::string	location,
		vector::GDALVectorWrapper *	p_existing,
		vector::GDALVectorWrapper *	p_access,
		std::string	layerName,
		double	buffInner,
		double	buffOuter,
		bool	force,
		bool	plot,
		std::string	filename )

This function conducts Systematic sampling on an input raster image.

First, the extent polygon of the raster is determined, then a random point is found within the polygon to act as the origin. An SQL query is conducted using one of the ST_SquareGrid, or ST_HexagonalGrid spatialite functions to create a grid of polygons of the user-specified shape. The grid is then rotated by a randomly generated rotation angle.

Next, the resulting grid polygons are iterated through, and a sample point is determined for each polygon depending on the user-defined location parameter (centers, corners, or random), and the samples are saved to an OGRLayer which is part of GDALDataset. Plot-required data is saved if plot is true (to later be utilized by the Python side of the application with matplotlib).

If the an access vector is given, then polygons of the accessible area are created, and each sample is check to ensure it falls within the accessible area.

If an existing vector is given, all of the sample points within the existing vector are added, and each point is checked to ensure it has not already been added by virtue of already existing as a sample point.

If the force parameter is given, every sample added is checked against the input raster to ensure the sample does not fall in a no data pixel. If it does the sample is thrown out. In the case where each grid cell is randomly sampled, 10 tries are allowed to find a point which is contains a data pixel otherwise that cell is not sampled.

Parameters

GDALRasterWrapper	*p_raster
double	cellSize
std::string	shape
std::string	location
bool	plot
std::string	filename

Returns

std::tuple< GDALVectorWrapper *, std::vector<std::vector<double>>, std::vector<std::vector<std::vector<double>>> >