POLYMODEL

Description

POLYMODEL is a simple math model that produces the best mathematical fit to a set of two-dimensional ground control points (GCPs).

Parameters

Name	Type	Caption	Length	Value range
MFILE *	String	Input file name, directory, or text file	1 - 192
DBGC	Integer	Input Ground Control Point segment or layer	0 - 1
ORDER	Integer	Transformation Order	0 - 1
MMSEG	Integer	Output math model segment or layer	0 - 1
REPORT	String	Report mode	0 - 192	Quick links

* Required parameter

Parameter descriptions

MFILE

Specifies a particular file or multiple files to be processed. Wildcards (*) can be used.

MFILE can be set using any of the following options:

A specific data file name or directory path and file name (for example, "irvine.pix" or "c:\data\irvine.pix").
A specific file name pattern or all of the files in a folder (for example, "c:\data\*.pix" or "c:\data").
An existing text file that contains references to multiple files with, optionally, different parameter settings on a per-file basis (for example, "c:\list.txt").

If the text file option is used, the following general rules apply:

Specify a .txt extension for the file containing multiple files and different parameter values.
List each set of parameters on its own line in the given order (see below).
Specify string parameters within quotation marks.
Do not specify numeric parameters within quotation marks.
A quotation mark preceded by a backslash is used as part of the string. For example, "ab\"c" is used as: ab"c.
Use an exclamation mark (!) before writing a comment in the text file.
Use semi-colons to delimit the parameters.
Leave the position between the semi-colons empty (";;") if you do not want to specify a value. Alternatively, if there are no remaining parameters to be specified on the end of a line, you may leave it blank.
Parameters in a text file may or may not be specified in the function:
- If a parameter is specified in the function and in the text file, the value provided in the text file is used.
- If a parameter is not specified in the text file, the parameter can be set in the function.

DBGC

Specifies the input GCP segment or layer to use when computing the model.

DBGC must be specified either in the task or in the text file. If a folder is specified for MFILE, this segment number applies to all images. If MFILE specifies a text file, the value for DBGC is read from the file; this parameter can therefore remain empty.

ORDER

Specifies the order of the transformation that is used to compute the two-dimensional polynomial model. Valid values are 1, 2, 3, 4, or 5. If the minimum number of GCPs is not provided for the specified transformation order, the next lowest order possible is used.

If a folder is specified for MFILE, this segment number applies to all images. If MFILE specifies a text file, the value for ORDER is read from the file; this parameter can therefore remain empty.

MMSEG

Specifies the output math model segment or layer in which to store the computed model.

If a folder is specified for MFILE, this segment number applies to all images. If MFILE specifies a text file, the value for MMSEG is read from the file; this parameter can therefore remain empty. If no value is specified, a new segment is created.

REPORT

Specifies where to direct the generated report.

Available options are:

TERM: generates a report on the terminal (default)
DISK: generates a report on file "IMPRPT.LST"
OFF: turns off report generation
<filename>: appends a report to the specified file

Details

POLYMODEL is a simple math model that uses a first-through-fifth order polynomial transformation, which is calculated based on two-dimensional GCPs. This math model produces the best-fit mathematically to a set of two-dimensional GCPs on an image.

The polynomial equations are fitted to the x- and y-coordinates of the GCPs by using least-squares criteria to model the correction in the image without identifying the source of the distortion. You may choose one of several polynomial orders, depending on the desired accuracy and the number of available GCPs.

First-order polynomial transformations can model a rotation, a scale, and a translation. Because a maximum of 21 additional terms can be added, providing a fifth-order polynomial, you can achieve more complex warping. Using a lower-order transformation, however, reduces the time needed to complete the correction and less geometric distortion can occur in areas without GCPs.

Example

Compute the polynomial model of an image.

EASI>mfile="xxx.pix"
EASI>dbgc=3
EASI>order=2
EASI>mmseg=
EASI>report=

EASI>r polymodel

Environments	PYTHON :: EASI :: MODELER
Quick links	Description :: Parameters :: Parameter descriptions :: Details :: Example