DENSITY

Description

Converts a point layer to a raster representative of either the density per square unit of the points or the density of an attribute (z-value) of the points.

Parameters

Name	Type	Length	Value range
InputPoints: Input vector segment *	Vector port	1 - 1
Bitmap: Input bitmap segment	Bitmap port	0 - 1
InputArea: Input georeferencing segment	GEO port	0 - 1
Output	Integer	0 - 1
Density	String	0 - 1	See Details Default: Square Kilometers
Sampling Radius *	Float	1 - 1	0.0 -
Maximum Neighbors	Integer	0 - 1	1 - Default: 10
Pixel X Size	Float	0 - 2
Pixel Y Size	Float	0 - 2
Density Per	String	0 - 1	POINT | ATTRIBUTE Default: POINT
Attribute	String	0 - 1
Report	String	0 - 192	See parameter description

* Required parameter

Parameter descriptions

InputPoints: Input vector segment

Specifies the vector segment that contains the input point layer.

Bitmap: Input bitmap segment

Specifies the bitmap segment to restrict the region when generating the weighted average. The results will be generated inside the bitmap segment (value 1) and pixels falling outside the bitmap (value 0) will be given a "No Data" value.

InputArea: Input georeferencing segment

Specifies the geoereferencing of the output raster channel. This specifies the projection, geographic extents, and the size (pixels/lines) of the resulting raster layer.

If this parameter is not set, the projection of the raster layer will be the same as the input point layer. The geographic extents of the raster layer will be determined based on the extents of the point layer and the specified Pixel X Size and Pixel Y Size parameters.

Output

Specifies the output raster channel to receive converted point layer.

If the output file already exists, the output channel must be specified and must already exist.

If the output file does not exist, this parameter is ignored.

The output channel must be 32-bit real (CHN_32R).

Density

Specifies the units for the calculated density.

Sampling Radius

Specifies the sampling radius, in meters, centered on each point in the raster channel to determine which points are used in the density calculation.

Maximum Neighbors

Specifies the maximum number of points closest to the center of the pixel and whose radii overlap the center of the pixel to be considered in calculating an output value.

Pixel X Size

Specifies the horizontal (X) pixel size, in meters, for the output raster channel.

This parameter is not required and is disabled if the georeferencing is specified by the InputArea parameter.

Pixel Y Size

Specifies the vertical (Y) pixel size, in meters, for the output raster channel.

This parameter is not required and is disabled if the georeferencing is specified by the InputArea parameter.

Density Per

Specifies whether to calculate the density for points or for an attribute.

If POINT is specified, the FLDNME (Attribute) value is ignored.

Attribute

Specifies the name of the attribute whose value is to be used to grid the polygons. If this parameter is specified as (Z-COORD), the z-coordinate of the first vertex of each vector shape is used. If the specified attribute does not exist and it is not Z-COORD, the ShapeID of the vector shapes are used for gridding.

This parameter is not used if the density type (DENSTYPE) is set to POINT.

Report

Specifies where to direct the generated report.

Available options are:

• LOG: generates a report on the terminal (default)
• <modulename.RPT>: appends a report to the module's RPT file
• DISK: generates a report on file "IMPRPT.LST"

Details

DENSITY generates a surface by applying a sampling radius to each point in the input point layer. No output values are calculated for areas lying outside the sampling radius.

The value for each pixel in the output raster is calculated based on the value of each point whose sampling radius overlaps the center of that pixel. You can specify the size of the sampling radius (SAMPRAD).

The density function is able to generate a surface representative of the density per square unit of the points or of the density of an attribute; for example, population.

If the number of points influencing the pixel is 1, then:

density is Z/PI*d^2

If the number of points influencing a pixel is greater than 1, then:

density is Z(i)/PI*d(i)^2