This program must be run in a LOCATION_NAME with an x,y coordinate system (i.e., a coordinate system with projection 0). For further information regarding this LOCATION_NAME type refer to the imagery manual entry.
The first prompt in i.tape.spot asks the user for the tape device name.
The next prompt is:
Please enter the following information
TAPE IDENTIFICATION: __
IMAGE DESCRIPTION: __
TITLE FOR THE EXTRACTED CELL (RASTER) FILES: __
AFTER COMPLETING ALL ANSWERS, HIT TO CONTINUE
(OR TO CANCEL)
This program automatically reads the satellite name, tape
product code, instrument name, interleaving indicator,
spectral mode, preprocessing level and work order number
into the field for TAPE IDENTIFICATION. The mission, path,
row, scene shift, scene center date and time, orientation,
incidence, azimuth, elevation angle, and absolute
calibration coefficients and offsets are automatically
entered into the field for IMAGE DESCRIPTION. User can
type in any other messages into the two sections and a
description as the title of raster map layer. The second
menu is:
SPOT IMAGE EXTRACT
Please select region of the image to extract
start row: 0______(1-3002)
end row: 0______(1-3002)
start col: 0______(1-3166)
end col: 0______(1-3166)
AFTER COMPLETING ALL ANSWERS, HIT TO CONTINUE
(OR TO CANCEL)
The numbers in parentheses are the total number of rows and
columns on the tape including zeros (filler). This
information and additional information can also be obtained
by running the program
m.examine.tape.
m.examine.tape
will read any tape and provide the user with the number of
files on a tape, the number of records on a tape, and the
record lengths. Any subset of the image on the tape may be
extracted. For a discussion of row and column extraction
see the subheading entitled
ROW AND COLUMN EXTRACTION below.
The next menu is:
Please mark an x by the bands you want extracted
_____ 1
_____ 2
_____ 3
AFTER COMPLETING ALL ANSWERS, HIT TO CONTINUE
(OR TO CANCEL)
SPOT imagery has three bands, but the user may want to extract
a subset of these bands. See the subheading in this entry
entitled
ROW AND COLUMN EXTRACTION.
The user then is asked to enter the prefix/group name for the raster band files to be created. This name will precede each band file extracted into GRASS. For example, if two bands are extracted the following two band files will result:
prefixname.1
prefixname.2
The specified prefixname will also automatically become the name for the imagery group file being created. Each image or subset (i.e., each run of i.tape.spot) should be given a unique prefix/group name.
The extraction process will begin by first skipping a number of files which are not data or not requested, advancing to the first band requested, forwarding to the requested column, and then reading the data. After extracting the requested rows and columns from each band, the program creates support files for the raster band map layer. The percent completion of the extraction is displayed on the screen. Because sometimes SPOT imagery is very large and is stored in multiple tape sets, the program is designed to read image by pausing when the tape need to be changed and inform the user to mount and load next tape. The number of tapes required to store one scene depends on the number of bytes per inch (bpi) in which the data are stored.
The extracted band files will be listed as raster map layers
available in the current MAPSET and may be displayed using the GRASS
commands
d.display,
d.rast, or
i.points.
ROW AND COLUMN EXTRACTION
The display options in GRASS allow the user to locate rows
and columns on the digital image. If enough disk space is
available, one band of an entire image or one band of a
portion of an image known to contain the area of interest,
can be extracted and displayed. The measurements
option in
d.display, or
d.where
(following use of d.rast)
will echo x and y coordinates to the screen. (These
coordinates will display negative numbers in the
north-south direction, but ignoring the negative sign will
yield the row number.) See the
imagery manual
entry for further explanation.
Each scene of a SPOT image contains filler on both the left and right sides of the quad. The user may want to identify the row and column numbers in order to exclude the filler. This filler will otherwise be extracted with the image and take up unnecessary disk space.
If a photograph of the digital image is available, the rows and columns to be extracted can be determined from it by associating inches with the total number of known rows and columns in the scene. For example, if the total length of the photograph is 12 inches, the total number of rows on the tape is 2000, and the northwest corner of the area of interest begins 2 inches from the top of the photo, then:
This program is interactive and requires no command line arguments.
d.display
d.rast
d.where
i.group
i.points
i.tape.mss
i.tape.mss.h
i.tape.other
i.tape.tm
imagery
m.examine.tape