CDSPOT

Description

Reads SPOT imagery from a SPOTIMAGE LGSOWG format CD when satellite orthorectification is required. CDSPOT automatically creates a PCIDSK file, reads all the requested imagery channels from CD, and saves the satellite path information in one or two segments. The output file from CDSPOT is used as input to SATMODEL and ORTHO.

Parameters

Name	Type	Caption	Length	Value range
CDDIR*	String	CD directory	1 - 191
FILE*	String	Output file name	1 - 191
CDIC*	Integer	CD input channel(s)	1 - 16
TEX1	String	File description	0 - 192
SPFILE	String	Output scene parameter file	0 - 191
ORBIT	Integer	Output orbit channel	0 - 1
REPORT	String	Report mode	0 - 192	Quick links
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* 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 is automatically created 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.

A SPOT panchromatic CD contains 1 channel and requires approximately 40Mb of disk space. A SPOT multispectral CD contains 3 channels and requires about 10 Mb of disk space (30 Mb for all 3 channels). Ensure that sufficient disk space is available before running CDSPOT.

Ranges of channels or segments can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

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

SPFILE

Specifies the file name for the output scene parameter text file. For the PCI satellite and orthorectification component, this parameter does not need to be specified. If the specified SPFILE already exists, the existing file is deleted before the new file is created.

ORBIT

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

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

MONITOR

The program progress can be monitored by printing the percentage of processing completed. A system parameter, MONITOR, controls this activity.

Available options are:

• ON: Turns the monitor ON (default)
• OFF: Turns the monitor OFF (recommended if running in batch or background mode)

Details

CDSPOT is part of the satellite orthorectification component. It reads SPOT imagery from a SPOTIMAGE LGSOWG format CD, when satellite orthorectification is required. CDSPOT automatically creates a PCIDSK file, reads all the requested imagery channels from CD, and saves the satellite path information in one or two segments. Output from CDSPOT is used with SATMODEL and ORTHO.

Level 1A provides the highest accuracy and should be used whenever possible. CDSPOT also supports the old SPOTIMAGE LGSOWG format and the new CAP-T format.

CDSPOT 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 that are required to hold all of the requested data. Ensure that sufficient disk space is available before running CDSPOT. In general, CDSPOT requires approximately 10Mb per specified channel for SPOT multispectral images, and about 40Mb for SPOT panchromatic images. A SPOT multispectral CD typically contains 3 channels; a SPOT panchromatic CD typically contains one channel.

The ORBIT parameter receives the number of the segment that contains the orbital and attitude information. The orbital and attitude information in this segment is required as input for SATMODEL and ORTHO. Level 1B CDs contain no attitude data.

For the PCI satellite and orthorectification component, the SPFILE parameter does not need to be specified.

Example

From a SPOT panchromatic left-view SPOTIMAGE format CD, perform orthorectification on the data. Extract channel 1 from the CD scene01 directory and store the data in the file 'irvine.pix'.

EASI>CDDIR="/cdrom/scene01/"   ! for UNIX machine
EASI>CDDIR="D:\SCENE01\"       ! for PC
EASI>CDDIR="[ABC.SCENE01]"     ! for VMX machine
EASI>FILE="irvine.pix"
EASI>CDIC=1
EASI>TEX1="Irvine  CD 1234"
EASI>SPFILE=
EASI>REPORT="irvine.txt"

EASI>R CDSPOT

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. and Carbonneau Y. "La multi-st\u00c3\u00a9r\u00c3\u00a9oscopie pour les corrections d'images SPOT-HRV", Canadian Journal of Remote Sensing, Vol. 15, No. 2 (September 1989) p110. (Also available in English from the Canada Centre for Remote Sensing.)