CDJERS1

Description

CDJERS1 reads JERS-1 SAR imagery from an LGSOWG CCT format CD, when satellite orthorectification is required. CDJERS1 automatically creates a PCIDSK file, reads all the requested imagery channels from CD, and saves the satellite path information in a segment. The output file from CDJERS1 is used as input to SATMODEL or ORTHO.

Parameters

cdjers1(cddir, file, cdic, tex1, orbit)

Name	Type	Caption	Length	Value range
CDDIR*	str	CD directory	1 -
FILE*	str	Output file name	1 -
CDIC*	List[int]	CD Input channel(s)	1 - 16
TEX1	str	Descriptive text	0 -
ORBIT	List[int]	Output orbit segment	0 - 1

* Required parameter

Parameter descriptions

CDDIR

Specifies the name of the CD directory that contains all input files.

FILE

Specifies the name of the PCIDSK file that will receive the processed data. This file will be created automatically and must not already exist.

CDIC

Specifies the list of channels or layers to read from the CD. Up to 16 channels may be specified.

For each channel, a corresponding channel is created in the output PCIDSK file. Duplicate channels are not allowed.

If this parameter is not specified, all channels will be read from the file.

TEX1

Optionally specifies a line of text that describes the file. Typically, this contains information that identifies the location of the data and the CD reference number.

If TEX1 is not specified, the File Header fields in the generated output PCIDSK image database hold the following information:

• FH5 receives the tape ID, satellite sensor, and satellite track
• FH7.1 receives the acquisition date and scene center (longitude and latitude, in decimal degrees)
• FH7.2 is empty

ORBIT

ORBIT is an output parameter. Upon completion, CDJERS1 writes the number of the output segment containing the orbital information to this parameter. This value may be used as input for other functions.

Details

CDJERS1 is part of the satellite orthorectification component. It reads JERS-1 SAR imagery from a LGSOWG CCT-format CD, when satellite orthorectification is required. CDJERS1 automatically creates a PCIDSK file, reads all the requested imagery channels from CD, and saves the satellite path information in a segment. Output from CDJERS1 is used with SATMODEL or ORTHO.

where "n" is a number between 1 and 9.

The JERS-1 CD provides access to different levels of geodetic processing and product types; to ensure the highest accuracy, select a level equivalent to the georeferenced level for use with CDJERS1. CDJERS1 currently works only with descending-order images.

Because a JERS-1 descending-order image is rotated 90 degrees counter-clockwise, CDJERS1 rotates the image back by 90 degrees when extracting the image. Because of this rotation process, processing time may seem longer when running CDJERS1 compared to other CD-reading modules.

CDJERS1 extracts from the CD the geographic coordinates of the scene center and the four corner points, as well as the corresponding pixel and line coordinates. The values are stored in the output orbit segment. These points can be used as ground control point (GCP) input for an approximate correction, which is useful when GCPs are unavailable for an area. Note, however, that using geographic coordinates may not produce very accurate results. To ensure an accurate calculation, a sufficient number of GCPs must be used for each scene or block of scenes.

The FILE parameter specifies the name of the PCIDSK file that holds the imagery and orbital information obtained from the CD. This file is automatically created with the dimensions required to hold all of the requested data. Sufficient disk space is required before running CDJERS1.

The ORBIT parameter receives the number of the segment that contains the orbital information. The orbital information in this segment is required as input for SATMODEL or ORTHO.

Example

The user has received an JERS-1 LGSOWG CCT georeferenced CD and wishes to perform orthorectification on the data. The user wishes to extract channel 1 from the CD, and store the data in the file "jers1.pix".

from pci.cdjers1 import *

cddir="scene001/"

file="jers1.pix"
cdic=[1]
tex1="Toronto, Ont. CD 1234"

cdjers1(cddir, file, cdic, tex1)

References

Toutin, Th. "Analyse math\u00c3\u00a9matique des possibilit\u00c3\u00a9s cartographiques du syst\u00c3\u00a8me SPOT". Th\u00c3\u00a8se de Docteur-Ing\u00c3\u00a9nieur en Sciences G\u00c3\u00a9od\u00c3\u00a9siques, ENSG, Paris, France, 1985. pp1 -163.

Toutin, Th., Carbonneau Y., and Laurent L.S. "An Integrated Method to Rectify Airborne Radar Imagery Using DEM Photogrammetric Engineering & Remote Sensing", Vol. 57, No. 4 (1982) p417-422.