Parent Topic: AVHRCOR

PARAMETERS

AVHRCOR is controlled by the following global parameters: 

Name     Prompt                                  Count     Type
FILI     Database Input File Name                1-64      Char
FILO     Database Output File Name               1-64      Char
DBIC     Database Input Channel List             1-1024    Int
DBOC     Database Output Channel List            0-1024    Int
DBIW     Database Input Window                   0-4       Int
DBOW     Database Output Window                  0-4       Int
AVHRRSEG AVHRR Calibration/Orbit Text Segment    0-1       Int
PIXRES   Output Pixel Resolution in Metres       0-1       Float
RESAMPLE Resample Mode: NEAR/BILIN/CUBIC/8PT     4         Char
MEMSIZE  Working Memory Size (Mbytes)            0-1       Float
TIMEMULT Multiplier for Start Scan Date Interval 0-1       Int

FILI

Specifies the name of the input file which contains the uncorrected AVHRR image data and the AVHRRSEG text segment. The input file must be a PCIDSK file (created using FIMPORT or MIAVHRR) or an actual Level 1b AVHRR disk file. 

 EASI>FILI="filespec"

FILO

Specifies the name of the output PCIDSK file which will receive the corrected image data. The output file must contain a georeferenced segment. 

 EASI>FILO="filespec"
If FILO does not exist, AVHRCOR will create a new output file whose extent will will be based on the 4 corner points of the input image. The new output file will be either in UTM (Universal Transverse Mercator) coordinates or UPS (Universal Polar Stereographic) coordinates, and use the WGS 84 datum. UPS is used when the input file contains data near or including a polar region. The reason for this is that UTM is not a suitable projection typically for data north of 75 degrees North latitude (or south of 75 degrees South latitude).

DBIC

Specifies the image channels in the input file (FILI) to correct. 

 EASI>DBIC=i,j,...,n
Ranges of channels can be specified with negative values. For example: {1,-4,10} is internally expanded to {1,2,3,4,10}. 

 Limits:
  Up to 1024 channels can be handled.
  Up to 16 integer values can be specified.

DBOC

Specifies the channels in the output file (FILO) to receive the corrected image data. 

 EASI>DBOC=i,j,...,n
Ranges of channels can be specified with negative values. For example: {1,-4,10} is internally expanded to {1,2,3,4,10}. 

 Limits:
  Up to 1024 channels can be handled.
  Up to 16 integer values can be specified.
  For each channel specified in DBIC, an output channel must
  be specified in DBOC.
  DBOC is ignored if FILO does not exist.
  Duplicate channels are NOT allowed.

DBIW

Specifies the window in the input file to use for the correction. This parameter is optional. By default, the input window is the entire input file. 

 EASI>DBIW=XOff,YOff,XSize,YSize 
 EASI>DBIW=0,0,2048,1000     ! Consider the first 1000 lines only.

DBOW

Specifies the window in the output file to register to. This parameter is optional. By default, the output window is the entire output file. DBOW is ignored if FILO does not exist. 

 EASI>DBOW=XOff,YOff,XSize,YSize 
 EASI>DBOW=0,0,2048,2000     ! Only register into the first 2000 lines.

AVHRRSEG

Specifies the text segment which contains AVHRR calibration and orbital data. This segment is automatically created when FIMPORT or MIAVHRR is used to read in an AVHRR image (from disk or tape, respectively). If AVHRRSEG is not set, AVHRCOR will try to find a valid AVHRR text segment in the input file to use. 

 EASI>AVHRRSEG=j     | Use segment number j
 EASI>AVHRRSEG=      | AVHRCOR will try to find a valid text segment

PIXRES

This parameter applies only when a new FILO is being created. It allows you to specify a pixel resolution or size (in metres) for the output file. By default, the pixel size is set to 1000m (e.g. 1000m x 1000m). The pixel size is used to determine the number of pixels and lines in the output file. Thus, decreasing the pixel size results in a larger output file and increased computation time. 

 EASI>PIXRES=4000        | Use a pixel size of 4km x 4km

RESAMPLE

Specifies the type of resampling of image data desired. The following methods are supported. 

 EASI>RESAMPLE="NEAR"    | Nearest Neighbour
 EASI>RESAMPLE="BILIN"   | Bilinear Interpolation
 EASI>RESAMPLE="CUBIC"   | Cubic Convolution
 EASI>RESAMPLE="8PT"     | Sin(x)/x with a  8 x  8 window
 EASI>RESAMPLE="16PT"    | Sin(x)/x with a 16 x 16 window

MEMSIZE

Specifies the size in Mbytes of internal working memory for AVHRCOR. In general AVHRCOR will run faster with larger amounts of memory, although AVHRCOR will work with any size of memory. 

 EASI>                           | use default value
 EASI>MEMSIZE=n                  | use n Mbytes
Ideally, the entire input image should be held in memory for AVHRCOR. However, this requirement would be unacceptable for large images on small computer systems. For example, a 5-channel, 2048x3000 size AVHRR image would require 2048x3000x5x2 = 60 Mbytes of RAM memory. Luckily, only a portion of the input image needs to be in RAM at any particular time. The size of the portion that needs to be in memory depends on the input image size and the amount of rotation between the input image and the geocoded output image.

TIMEMULT

Specifies a multiplication factor which can be used to increase the search time interval in which AVHRCOR tries to look for the exact starting scan date of the input image. By default, TIMEMULT is set to 1, which indicates that a default search interval of 60 minutes should be used. 

 EASI>TIMEMULT=        | Use a default search interval of 60 minutes
 EASI>TIMEMULT=2       | Use a search interval of 120 minutes
Parent Topic: AVHRCOR
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