Parent Topic: MIAVHRR
PARAMETERS
MIAVHRR is controlled by the following global parameters:
Name Prompt Count Type
FILE Database File Name 1-64 Char
MTIC Mag Tape Input Channel List 0-5 Int
DBOC Database Output Channel List 0-5 Int
MTIW Mag Tape Input Window 0-4 Int
DBOW Database Output Window 0-4 Int
AVHRRSEG AVHRR Calibration/Orbit Segment 0-1 Int
DBGC Database Ground Control Segment 0-1 Int
STARTFIL Start File on Tape 0-1 Int
The following parameter receives output:
LASC Last Database Segment Created 1 Int
FILE
Specifies the name of the PCIDSK image database to receive imagery
from tape.
EASI>FILE="...filename..."
- The image database file will be created if it does not exist.
- The created database will have the size specified by MTIW and a
number of signed 16-bit channels equal to the number of input
channels specified by MTIC.
- The syntax of the filename is system dependent.
MTIC
Specifies the image channels to be read from the input tape.
EASI>MTIC=i,j,...,p
EASI>MTIC= | defaults to 1,...,# of tape channels
- Up to 5 channels can be specified.
- Ranges of channels can be specified with negative values. For
example: {1,-4} is internally expanded to {1,2,3,4}.
- Note that MTIC values do not necessarily correspond to AVHRR band
numbers. For example, a Level1b tape may contain only a subset of
the 5 AVHRR bands (channel selection option). As an example, a
tape may only contain AVHRR bands 4 and 5. In this case, MTIC
should be either defaulted or set to 1,2 in order to read these
two bands.
DBOC
Specifies the image channels to receive output from tape.
EASI>DBOC=i,j,...,p
EASI>DBOC= | defaults to newly created file channels
- The number of values in DBOC must be equal to the number of
channels specified by MTIC.
- Up to 5 channels can be specified.
- Ranges of channels can be specified with negatives values. For
example: {1,-4} is internally expanded to {1,2,3,4}.
- DBOC must be set if FILE exists.
- If FILE is created by MIAVHRR, DBOC will be reset with the
channel numbers of the created file.
- The output channels can be of any type, but signed 16-bit integer
is recommended because AVHRR pixel values are 10-bit in size
(with values ranging from 0 to 1023). If an output channel is
8-bit (with values ranging from 0 to 255), then 10-bit AVHRR
pixel values will be scaled to fit into that output channel. This
scaling is achieved by dividing each 10-bit pixel value by 4. In
this instance the text segment LUT associated with this 8-bit
output channel will be set. The LUT maps 10-bit pixel values to
8-bit pixel values. A warning message indicating that scaling
will occur is issued for each output channel which is 8-bit. Note
that text segment LUTs are labelled by AVHRR channel number, not
output channel number. For example, if AVHRR channel 3 is read
into output channel 8, then LUT number 3 will be created in the
text segment.
MTIW
Specifies a rectangular subset of the image on the input tape.
EASI>MTIW=Xoffset,Yoffset,Xsize,Ysize
EASI>MTIW= | defaults to entire image on tape
- The offset + size must not exceed the image size.
DBOW
Specifies a rectangular subset of the image on the output file.
EASI>DBOW=Xoffset,Yoffset,Xsize,Ysize
EASI>DBOW= | defaults to entire image
- The offset + size must not exceed the image size.
- If DBOW is different in size from MTIW, shrinking or zooming will
be performed automatically. In this situation, no GCP segment
will be created.
- If a new file is created by MIAVHRR, DBOW will be reset to be the
same size as MTIW.
AVHRRSEG
Specifies the text segment to receive the AVHRR Calibration/Orbit
data.
EASI>AVHRRSEG=j
EASI>AVHRRSEG= | new segment will be created
This text segment (type 140), named "AVHRRSEG" contains calibration
and orbital data such as:
- Satellite ID (name), orbit ID, year, day of year.
- Upper left and lower right image LONG/LAT coordinates (spatial
extent information).
- A single GCP corresponding to the exact center of the middle
pixel from the first line of the output image.
- Orbital element/ephemeris data: epoch, inclination, right
ascension, argument of perigee, eccentricity, mean motion, mean
anomaly.
- Ascending/descending orbit flag.
- Platinum resistance temperatures.
- Internal target values for channels 3,4,5.
- Grey level of space values for channels 3,4,5.
- Up to 5 LUTs used to compress 10-bit data to 8-bit. If a
particular output channel is not 8-bit, no LUT for that channel
will be created. These LUTs are used by the program, SST.
All values are computed over the input window.
Some of the information contained in the text segment is not
available for certain tape formats. In these instances, default
values will be placed into the text segment as placeholders. If and
when this information can be obtained by other means, the text
segment can be edited to fill in the missing information. For
example, the AES 10-bit and AES TeraScan formats do not provide GCP
data. Hence the single GCP reported in the text segment will be
given a default (invalid) value. If an actual GCP can be acquired
later, the default GCP value in the text segment can be replaced
with the proper value. This will enable the operation of other
programs, such as AVHRCOR, which expect a valid GCP to be present in
the MIAVHRR text segment.
DBGC
Specifies the database GCP segment to receive the ground control
points. Elevation values are set to 0. Only Level 1b LAC/HRPT and
GAC formats provide GCP data. For these formats, up to 255 GCPs are
taken from the input window (up to 17 GCPs per line and up to 15
lines from the input window). Each GCP in the DBGC segment actually
consists of a X/Y coordinate pair and a corresponding lat/long
coordinate pair. The X/Y coordinate values are similar to pixel/line
coordinates except that X/Y coordinate values begin at 0.0 (as
opposed to 1) and do not have to be integral. This allows the
specification of points within a pixel as a GCP (for increased
accuracy). As an example, consider a 200 pixel by 100 line image.
The center of the top-left pixel in this image would have X/Y
coordinates of (0.5, 0.5). The center of the bottom-right pixel
would have X/Y coordinates of (199.5, 99.5). The exact center of the
image would have X/Y coordinates of (100.0, 50.0). The single GCP
reported in the AVHRRSEG text segment also follows this format.
EASI>DBGC=i
EASI>DBGC= | new segment will be created
If MTIW is different in size from DBOW, no GCP segment is written.
STARTFIL
Specifies the number of tape files to skip before reading the
scene/image. If STARTFIL is 1, no files are skipped. If STARTFIL is
"n", then n-1 tape files will be skipped before reading begins.
STARTFIL is used to advance the tape position to the scene that you
wish to import (for tapes containing multiple scenes). STARTFIL is
typically set to 1, in order to read the first scene on a tape. This
is the default value. If STARTFIL is not specified, or is less than
1 in value, it will be reset to 1. Note that MIAVHRR never does any
rewinding of the tape. This allows consecutive scenes to be read off
a tape without any rewinding between scenes (as long as STARTFIL is
set properly each time).
EASI>STARTFIL= | start reading at 1st file on tape
EASI>STARTFIL=1 | start reading at 1st file on tape
EASI>STARTFIL=n | start reading at nth file on tape
For the AES TeraScan format, STARTFIL should be an odd number.
EASI>STARTFIL=3 | second AES TeraScan file on tape
For the CEOS format, STARTFIL should be 1, 6, 11, and so forth. Some
CEOS tapes have an initial 100 byte header record which should be
skipped. In this case, STARTFIL should be 2, 7, 12, and so forth. A
CEOS scene/image always begins with "5 records of 360 bytes".
An example of MAGSTRU output for a CEOS format tape is shown below:
1 records of 100 bytes <- not part of CEOS format
*** EOF ***
5 records of 360 bytes <- STARTFIL = 2 (Scene/Image 1)
*** EOF ***
6 records of 2520 bytes <- leader file
*** EOF ***
3019 records of 21872 bytes <- imagery options file
*** EOF ***
6 records of 4140 bytes <- trailer file
*** EOF ***
1 records of 360 bytes <- null volume directory file
*** EOF ***
5 records of 360 bytes <- STARTFIL = 7 (Scene/Image 2)
*** EOF ***
6 records of 2520 bytes
*** EOF ***
... ... ...
... ... ...
LASC
The segment number of the last created segment is saved in this
output parameter for use by other EASI procedures. For example, if
MIAVHRR creates a new text segment (segment number 2) and a new GCP
segment (segment number 3), then LASC will be set to 3.
Parent Topic: MIAVHRR
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