ADJDEM

Description

ADJDEM adjusts an extracted digital elevation model (DEM) by using points with elevation information that you provide. Each elevation value is adjusted according to the heights of the reference points. ADJDEM is especially useful for removing systematic errors in a DEM.

Parameters

Name	Type	Length	Value range
InputDEM: Input elevation channel or layer *	Raster port	1 - 1
InputGCP: Input reference GCPs *	GCP port	1 - 1
InputVEC: Input reference points *	Vector port	1 - 1
Output: Adjusted DEM layer *	Raster port	1 - 1
Polynomial Order	Integer	0 - 1	1 - 2 Default: 1
Failure Value	Integer	0 - 1	Default: -100
Background Elevation Value	Real	0 - 1	Default: -150
Field Name	String	0 - 1	ATTRIBUTE, ELEVATION, ZCOORD Default: ATTRIBUTE
Report	String	0 - 192	See parameter description

* Required parameter

Parameter descriptions

InputDEM: Input elevation channel or layer

The input DEM channel or layer to adjust.

InputGCP: Input reference GCPs

The GCP segment to use to adjust the existing values of the DEM.

InputVEC: Input reference points

The vector segment that contains the input reference points and attribute data.

Output: Adjusted DEM layer

The output layer that will contain the adjusted DEM.

Polynomial Order

The order to use for the surface fit to the DEM.

Failure Value

The gray-level value that represents the failure value inside the DEM. This value is usually the one used during DEM extraction.

Background Elevation Value

The gray-level value that represents the background value inside the DEM. This is usually the value used during DEM extraction.

Field Name

The name of the attribute from which the value will be used to adjust the extracted DEM.

When you specify ZCOORD, the z-coordinate of the first vertex of each vector shape is used. The default is ATTRIBUTE.

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

ADJDEM adjusts an extracted DEM by using reference elevation values, such as SPOT elevation values. The algorithm first computes the errors between the extracted DEM and the reference DEM. A first-order or second-order two-dimensional polynomial surface is then fitted to the errors. Each elevation value within the input window is then adjusted according to the fitted surface. ADJDEM is especially useful for removing systematic errors in a DEM.

You can choose between a first-order and second-order polynomial surface fit. You must also specify the failure value and the background elevation value in the DEM to ensure that these values are not adjusted.

ADJDEM will produce an RMS-error report before and after adjustment when you specify a value of ON for the Report Mode (REPORT) parameter. The default name of the report is adjdem.rpt; however, you can overwrite the default with a file name you specify.