ELEVRMS

Description

ELEVRMS reads elevations from a digital elevation channel and compares the elevations with elevation values from a given GCP (ground control point) or vector segment. The root mean square (RMS) error is generated in a report.

Parameters

elevrms(file, dbec, dbseg, backelev, fldnme)

Name	Type	Caption	Length	Value range
FILE *	str	Input file name	1 -
DBEC *	List[int]	Input elevation channel	1 - 1
DBSEG *	List[int]	Input reference segment	1 - 1
BACKELEV	List[float]	Background elevation value	0 - 1
FLDNME	str	Field Name	0 - 64	ATTRIBUTE | Z-COORD Default: ATTRIBUTE

* Required parameter

Parameter descriptions

FILE

Specifies the name of the PCIDSK image database file that contains the input segment.

DBEC

Specifies the image channel in FILE that contains the digital elevation data.

DBSEG

Specifies the input GCP or vector segment in FILE.

BACKELEV

Optionally specifies the background elevation value (or no-data value) in the DEM elevation channel (DBEC). Pixels having this value will not be compared with the elevation values in the input GCP or vector segment (DBSEG). This permits the omission of specific regions when computing the root mean square error.

FLDNME

Specifies the attribute field or the z-coordinate from which elevation values should be extracted, if the input reference segment is a vector segment.

Details

This program generates an RMS error report between the extracted DEM from satellite images or airphotos and the input elevations from an input GCP or vector segment with an attribute or z-coordinate as the elevation.

The FILE parameter specifies the name of the PCIDSK file that contains the extracted elevations. This file may be either georeferenced or non-georeferenced. The input file must contain the digital elevation channel (DBEC) and the input reference segment (DBSEG). The reference segment may be a GCP segment (type 214) or a vector segment (type 116). If it is a vector segment, either an attribute field or the z-coordinate may be used as the source of the elevation values. The georeferencing of the file and the input segment must be compatible to compute the RMS report.

The BACKELEV parameter specifies the background elevation value in the digital elevation channel in which the elevation will not be compared with the values in the input segment. This permits the omission of specific regions when computing the RMS error.

Example

The user has extracted the DEM of the file "irvine.pix" and the results are stored in channel 3 of the file. The user wants to compare the extracted digital elevation with the input GCP segment stored in segment 2 of the file. The background elevation value is -20.

from pci.elevrms import elevrms

file		=	"irvine.pix"
dbec		=	[10]
dbseg		=	[27]
backelev	=	[-20]
fldnme		=	""

elevrms( file, dbec, dbseg, backelev, fldnme )