SIGMERG

Description

Merges two class signatures to create a new class signature. The user can specify a gray-level value, threshold, and 'a priori' probability for the new signature class.

Parameters

Name	Type	Caption	Length	Value range
FILE *	String	Input file name	1 - 192
DSIG *	Integer	Input class signature segments	2 - 2
VALU	Integer	Gray-level values	0 - 1	1 - 254
THRS	Float	Gaussian threshold	0 - 1
BIAS	Float	Class bias	0 - 1
DBSN	String	Output segment name	0 - 8
DBSD	String	Output segment description	0 - 64

* Required parameter

Parameter descriptions

FILE

Specifies the name of the PCIDSK image file that contains the signatures to merge, and to receive the output merged signature.

DSIG

Specifies the two class segment segments (type 121) to merge.

Specified segments must have the same number and set of channels.

VALU

Specifies an integer value (1-254) that represents the class in the output classification theme map created by MLC.

Values of 0 and 255 are invalid, as they will be assigned to the null and multiply-classified pixels of the output theme map, respectively.

If this parameter is not specified, the value is inherited from the value held in the first input signature segment (DSIG1).

THRS

Specifies the Gaussian feature-space threshold. The greater this value is, the larger the hyperellipsoid or parallelepiped in feature space.

This value is a REAL number in units of standard deviation.

If this parameter is not specified, the value is inherited from the value held in the first input signature segment (DSIG1).

BIAS

Specifies the BIAS, or relative 'a priori' probabilities for the class. If all classes have equal bias, their 'a priori' probabilities are equal.

This parameter "biases" the maximum likelihood classifier's assignment of a class to a point that lies in overlapping classes in feature-space. This value is a REAL number.

If this parameter is not specified, the value is inherited from the value held in the first input signature segment (DSIG1).

DBSN

Specifies a name (up to 8 characters) for the output segment.

If this parameter is not specified, the value is inherited from the value held in the first input signature segment (DSIG1).

DBSD

Describes (in up to 64 characters) the contents or origins of the output data.

If this parameter is not specified, the value is inherited from the value held in the first input signature segment (DSIG1).

Details

SIGMERG merges two existing signature class segments (DSIG) to create a new signature segment.

The merged signature's value (VALU), threshold (THRS), bias (BIAS), segment name (DBSN), and segment description (DBSD) may be specified by the user. Any values not specified will be inherited from the corresponding values of the first input signature segment.

Use SIGMERG for the aggregation of class signature segments, rather than for merging training area bitmaps and creating signature segments. Certain limitations, however, should be recognized. First, the two signature segments used for merging must have been created using the same number and set of input channels. Second, if the two signatures used as input were created from overlapping training area bitmaps, the results will be erroneous, because the overlap area will be sampled twice.

Example

Merge signature segments 21 and 22, in the file 'irvine.pix'.

EASI>file	=	"irvine.pix"	! input file
EASI>dsig	=	21,22	! input signature segments
EASI>valu	=		! inherit value from signature 21
EASI>thrs	=		! inherit value from signature 21
EASI>bias	=		! inherit value from signature 21
EASI>dbsn	=		! inherit value from signature 21
EASI>dbsd	=		! no segment description
EASI>run SIGMERG