VECSEL

Description

Parameters

Parameter descriptions

Input: Vector layer to process

The vector layer to process.

Output: Output vector segment

The vector segment to which to write the selected vectors.

Inclusive operation

Whether or not the vector selection is inclusive.

Use georeferencing bounds

Whether to use the bounds specified in the georeferencing segment of the input file as the clip window.

Input window

The vector window (x-offset, y-offset, x-size, y-size) in which to clip the vectors.

If no value is specified for this parameter, the entire channel is used by default. Window units are expressed according to the units defined in the input vector segment (for example, METER or UTM). The x-offset and y-offset define the upper-left starting point of the window. X-size defines the window width and y-size defines the window height. You must specify all four values.

If On is selected in the Use georeferencing bounds list, this parameter is ignored.

This parameter is optional.

List of attribute ranges

The ranges of attributes for selection of the input vector data.

You specify ranges in pairs of values. In each pair, the first value defines the start of the range and the second value defines the end of the range. If you specify an odd number of values, the last value is used as a range of one value.

1,1,20,31.7,41.3

This parameter is optional.

Thin percentage

The percentage of vector data to drop, or thin. This is useful for reducing the number of vertices in the vector set. You can specify the value in a range from 0 through 99.9. By default, no thinning is applied, which retains all of the data.

For more information, see Vector thinning.

This parameter is optional.

Vector layer name

The name of the new vector segment.

If no value is specified for this parameter, VECSEL uses the name of the input vector segment and copies it to the output.

This parameter is optional.

Vector layer description

The contents or origins of the new vector data.

If no value is specified for this parameter, VECSEL uses the description of the input vector segment and copies it to the output.

This parameter is optional.

Field name

The field name to use for range selection.

You must specify a value for this parameter to select values based on attributes. In addition to any existing numeric attribute, a special value, ShapeID, is also supported.

The names are not case-sensitive.

With the parameters specified as such, VECSEL selects all the vectors having a value of 100 to 1000 in the field named "Elevation".

For example, suppose you specify the Field name parameter as Elevationand the List of attribute ranges parameters as 100,1000. With the parameters specified as such, VECSEL selects all the vectors having a value of 100 to 1000 in the field named "Elevation".

This parameter is optional.

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

VECSEL extracts vectors from an existing vector segment, as specified by a window, one or more ranges of attributes, or both. The vectors are extracted as output to a new vector segment. No changes are made to the input vector segment. You can use VECSEL to split up imported vector data that may be too large for other vector functions. You can also perform vector thinning on the output vectors.

The input file contains the input vector segment to process. The type of vector selection process is specified by the inclusive operation. By default, VECSEL includes as output all vector data values in the specified window, one or more ranges of attributes, or both. However, you can also exclude the vector data values, if necessary.

The inclusive operation governs selection by both window and attribute ranges, if both are specified. In such cases, it may be advantageous to run VECSEL twice: once for the window selection, and a second time using the output from the first run as input to the second run for the attribute ranges.

You can define an area of vector processing by using the georeferencing segment in your input file or by the input window you specify. However, if you elect to use georeferencing bounds, and also specify an input window, the input window will be ignored. If you specify neither georeferencing bounds nor an input window, VECSEL processes all of the vectors, regardless of their location in the input file. The units of the window are those of the input vector segment, such as UTM.

Vectors can be processed by their attribute value, specified as a list of attribute ranges. If no attribute range is specified, all of the vectors are processed, regardless of their attribute value.

To thin vertices from the output vectors, you can specify a percentage to thin. For more information, see Vector thinning.

If you run VECSEL as an inclusive operation, all vector data on or within the window, if specified, and on or within the attribute range or ranges, if specified, are retained in the output vector segment. If you run VECSEL as an exclusive operation, all vector data on or outside the window, if specified, and outside the attribute range or ranges, if specified, are retained in the output vector segment.

Vector thinning

To thin vertices from the output vectors, you can specify a percentage to thin. The percentage can be any value ranging from 0 through 99.9.

During processing, VECSEL samples the vertices, as specified. For example, a value of 50 drops every other vertex in the output vector. A value of 25 drops every fourth vertex.

The algorithm preserves all line and point structures by always retaining both end points in a line and all points. Only vertices between end points in a line are eligible for thinning.

For an example that applies vector thinning, see this example that applies vector thinning.