APS

Alter pixel size

Environments	PYTHON :: EASI
Quick links	Description :: Parameters :: Parameter descriptions :: Details :: Examples :: Related

Description

Alters the ground pixel size (in meters) for the database file. APS works only if georeferencing units are either PIXEL or LONG/LAT. If georeferencing units are anything else (such as UTM or METER), use GEOSET to alter the pixel size.

Parameters

aps(file, pxsz)

Name	Type	Caption	Length	Value range
FILE *	str	Input file name	1 -
PXSZ *	List[float]	Pixel ground-size, in meters	2 - 2	Default: 1.0,1.0

* Required parameter

Parameter descriptions

FILE

Specifies the name of the PCIDSK image file to be altered.

PXSZ

Specifies the horizontal (x) and vertical (y) dimensions of one image pixel, in meters.

Setting this size to a meaningful value is important for ground area calculations (in classification, for example).

Details

APS modifies the pixel ground size (PXSZ) for a specified image database (FILE). It overwrites the pixel size that was specified when the file was created by CIM. The pixel ground size is used for generating statistics and ground area calculations of classified data (performed by MLC and MLR).

APS alters the pixel size on a database file only if the output units for the georeferencing segment are "PIXEL" or "LONG/LAT". This avoids the possibility of inconsistency between the pixel size stored in the master header of the database file and the pixel size derived from the georeferencing segment.

There are two options for changing the pixel size in database files for which georeferencing units are "UTM" or "METER":

Change the UPLEFT and LORIGHT parameters, and run the GEOSET program. GEOSET calculates the pixel size, given the values specified for UPLEFT and LORIGHT, and saves the pixel size on the database file.
Default the UPLEFT and LORIGHT parameters, set MAPUNITS="PIXEL", and run the GEOSET program. This process resets the georeferencing segment to the identity transform. Then, run APS to change the pixel size.

Examples

Alter the ground size of the pixels in the file MSS.PIX to 30 meters in the x-direction and 40.3 meters in the y-direction, assuming that MSS.PIX has not been georeferenced.

from pci.aps import aps

file = "mss.pix"
pxsz = [30,40.3]

aps( file, pxsz )

Change the pixel size of the demo image file irvine.pix to 5 by 5 meters. You must run GEOSET first, to default the georeferencing transform.

from pci.geoset import geoset

file = "irvine.pix"
upleft = []
loright = []
mapunits = "PIXEL"

geoset( file, upleft, loright, mapunits )

Use APS to alter the pixel size.

from pci.aps import aps

file="irvine.pix"
pxsz=[5,5]

aps( file, pxsz )