MSPOTC -- Magtape Canadian SPOT Format

Reads SPOT imagery from a LGSOWG format tape produced in Canada, when satellite orthorectification is required. MSPOTC automatically creates a PCIDSK file, reads all of the requested imagery @@channels@@ from tape, and saves the satellite path information in one or two @@segments@@.

The output file from MSPOTC is used as input to the programs SMODEL and SORTHO.

Note: The MIL program can also be used to read LGSOWG format tapes in a more general way; however, output from MIL cannot be used for orthorectification.

@@ifpace Progress of this program can be monitored. See MONITOR section.

@@ifpace

PARAMETERS

MSPOTC is controlled by the following global parameters:

Name     Prompt                                  Count     Type
FILE     Database File Name                      1-64      Char
MTIC     Mag Tape Input Channel list             1-16      Int
TEX1     Database Descriptive Text 1             0-64      Char
REPORT   Report Mode: TERM/OFF/filename          1-64      Char

The following parameters receive output:

ORBIT    Orbit Segment                           1         Int

FILE

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

 EASI>FILE="filespec"

MTIC

Specifies the list of channels to read from the tape. For each channel specified, a channel will be created on the PCIDSK file (FILE).

 EASI>MTIC=i,j,...,p

There is 1 channel on a SPOT panchromatic tape, and there are 3 channels on a SPOT multispectral tape. SPOT panchromatic requires about 40 Mbytes of disk space, and SPOT multispectral requires about 10 Mbytes of disk space (30 Mbytes for all 3 channels). This amount of space must be available before MSPOTC is run.

TEX1

Optionally specifies a line of text describing the file. Typically this would contain information identifying the location of the data and the tape reference number.

 EASI>TEX1="string"

Note: If TEX1 is defaulted, the following fields of the File Header in the output PCIDSK image database created will hold the following information:

FH5   receives the tape ID, satellite Sensor and satellite Track.
FH7.1 receives the acquisition Date and scene Centre (longitude,
      latitude in decimal degrees.)
FH7.2 will be blanked for now.

REPORT

Specifies where the tape information report should be directed. This report contains tape header and orbital information.

 EASI>REPORT="filename"
 EASI>REPORT=            | defaults to terminal output

Note: The following names have special meaning:

 EASI>REPORT="TERM"      | generates reports on your terminal
 EASI>REPORT="DISK"      | generates reports on file "IMPRPT.LST"
 EASI>REPORT="OFF"       | switch off report generation

ORBIT

This parameter receives the number of the segment in which the orbital information was saved.

DETAILS

The MSPOTC program is part of the satellite orthorectification package. It is used to read SPOT imagery from a LGSOWG format tape produced in Canada, when satellite orthorectification is required. MSPOTC automatically creates a PCIDSK file, reads all of the requested imagery channels from tape, and saves the satellite path information in one or two segments. Output from MSPOTC is used with the SMODEL and SORTHO programs.

The Canadian LGSOWG tape makes available different levels of processing. This program supports the level 1 and georeferenced tapes. Level 1 is radiometrically corrected, with detector offsets applied; georeferenced is radiometrically corrected, with across and along track geometric corrections applied. Level 1 tape is always recommended for highest accuracy. Georeferenced tapes may produce large errors.

NOTE : This program only support tapes generated by CCRS. Tapes generated by MDA-RICHMOND MERIDIAN format are not supported.

Level 1 tape has two different volumes: imagery and supplemental. The imagery logical volume contains the imagery data itself, and related image-synchronized information, plus ONLY that support data related to the scene. Ephemeris and attitude data are specifically excluded from this volume, as is station-specific information, such as annotation data. The supplemental logical volume contains station-related processing data, such as annotation, ephemeris and attitude data, and GCP and Payload Correction (PCD) information. The user should expect to find differences in the definition of this logical volume as supplied by different agencies. The supplemental volume is usually optional (user's choice) and may come before or after the imagery logical volume. For this program, it is recommended that the user supply the supplemental volume in order to improve the accuracy of the results. If the supplemental volume is not used, approximate values will be used in the program. For a georeferenced tape, a supplemental volume is not needed.

The MSPOTC program will extract from the tape the geographic coordinates of the scene centre and the 4 corner points, and the corresponding pixel and line positions, if the values are available. The values are stored in the ORBIT segment. These points can be used as GCPs input to the SMODEL program for an approximate correction. It is useful for the case where the user cannot obtain any GCPs for an area. Since the geographic coordinates are not very accurate, the user should not expect very accurate results if those points are used.

The FILE parameter is used to specify the name of the PCIDSK file to hold the imagery and orbital information read off tape. This file is automatically created with the dimensions required to hold all of the requested data. The user should ensure that sufficient disk space is available before MSPOTC is run. Typically this is about 10 Mbytes per channel requested in parameter MTIC for SPOT multispectral, and about 40 Mbytes for SPOT panchromatic.

Note: Typically there are 3 channels on a SPOT multispectral tape, and there is 1 channel on a SPOT panchromatic tape. The MSH program can be run to check the number of channels on tape.

The ORBIT parameter receives the segment number which contains the orbital and attitude information. The orbital and attitude information are required as input to the SMODEL and SORTHO programs. There is no attitude data for georeferenced data.

When MSPOTC reads the imagery data off the `georeferenced tape', some basic processing is performed to prepare it for orthorectification. Scan lines are left shifted (removing the rough earth rotation correction applied), and all `black' edge pixels are discarded. This results in a data file which is narrower than the image size on tape and which is visually different than the output from the MIL tape reading program (which is in the PACE Tape I/O package).

PCI wishes to acknowledge the assistance of Dr. Thierry Toutin and Yves Carbonneau at Canada Centre for Remote Sensing for providing source code and assistance of their programs. For more information about the method, please see the following papers:

 Toutin, Th, 1985.  Analyse mathematique des possibilites
 cartographiques du systeme SPOT, These de Docteur-Ingenieur
 en Sciences Geodesiques, ENSG, Paris, France, pp 1-163.

 Toutin, Th. & Carbonneau Y.  La Multi-Stereoscopie Pour Les
 Corrections D'Images SPOT-HRV, Canadian Journal of Remote
 Sensing, p110, Vol. 15, No. 2 September, 1989.
 (This article is also available in English from the Canada
 Centre for Remote Sensing.)

EXAMPLE

The user has received a SPOT multispectral format tape and wishes to perform orthorectification on the data. To get a preliminary printout of the tape header and orbital information, the MSH program in the Tape I/O package can be run (this is optional).

 EASI>REPORT=
 EASI>STARTFIL=1
 EASI>RUN MSH

The user wishes to extract channels 1 and 3 from the tape and store them in the file sherbrooke.pix. Note: the created file will be approximately 2 * 20 Mbytes = 40 Mbytes.

 EASI>FILE="sherbrooke.pix"
 EASI>MTIC=1,3
 EASI>TEX1="sherbrooke,  Tape 1234"
 EASI>REPORT="sherbrooke.txt"
 EASI>R MSPOTC

After the tape has completed reading, the text report file sherbrooke.txt could be printed using a print utility on your system, and the REPORT parameter should be reset to the terminal:

 EASI>REPORT="TERM"

The file sherbrooke.pix could now be used as input, along with collected ground control points, to the programs SMODEL and SORTHO.

NOTES ON ACCESSING TAPE DRIVES:

If you have trouble accessing the tape drive, you may have to set up the MT00 and MT0: parameters to allow tape reading programs (such as MSH and MSPOTC) to access the drive. This is described in the Installation manual that was supplied with the PCI EASI/PACE software and should have been done by your system manager. In general you would do the following:

 EASI>MT00="MT0:"
 EASI>MT0:="device_name"    |e.g., "/dev/rmt0" on some UNIX systems

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