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WXP Image File

This type of file is a generic image format that can be displayed with the WXP xsat satellite display program. This can be used to import image data into WXP.

FORMAT

The format of the file is as follows:

WXPIMG
date
info
proj clat clon dx dy nx ny
image...

Header Data

The first line of the file is the string:

WXPIMG

which is used to determine file type. The second line of the data file is a character string describing the valid time and origin of the image (less than 50 characters). Examples:

1215Z 4 AUG 98
ISCCP analysis valid 00Z 2 JUN 90

The third line contains a character string describing the contents of the image (less than 50 characters). Examples:

GOES East IR 11um
Integrated Cloud Coverage (%)

The fourth line contains image size and location in the following format:

proj[:param] clat clon dx dy nx ny
or
nx ny

Where:

  • proj -- The projection:
    LL -- lat-lon,
    PS -- polar stereographic,
    ME -- mercator,
    LC -- lambert conformal,
    SAT -- satellite projection. (see plot_domain section of Users Guide for more projections)
  • param -- The projection parameters (see plot_domain section of Users Guide).
  • clat -- The central latitude (N) of the grid.
  • clon -- The central longitude (E) of the grid.
  • dx -- The X coordinate pixel spacing based on projection.
  • dy -- The Y coordinate pixel spacing based on projection.
  • nx -- The number of pixels in the X direction.
  • ny -- The number of pixels in the Y direction.

Examples:

ME 30.0 -100.0 0.187793 0.187793 640 427
LL 0.0 0.0 2.5 2.5 144 72
1000 760
(if not geographic data, just specify size)

An example of the five line header is listed below:

WXPIMG
0615Z  9 AUG 98
GOES NH Infrared 11um
ME 30.000000 -100.000000 0.187793 0.187793 640 427

WXPIMG
ISCCP analysis valid 00Z 2 JUN 90
Integrated Cloud Coverage (%)
LL 0.0 0.0 2.5 2.5 144 72

Image Data

The image follows a newline character terminating the projection line. The image is binary, stored 8 bits per pixel which gives an intensity range of 0 to 255. The size of the image is defined by ny, number of scan lines, and nx, number of elements per scan line. Therefore, there are nx bytes per scan line. Each pixel/byte is saved from left to right on the scan line. Each scan line is stored consecutively from top to bottom.

EXAMPLES

A sample image file would look like:

WXPIMG
0615Z  9 AUG 98
GOES NH Infrared 11um
ME 30.000000 -100.000000 0.187793 0.187793 640 427
vssqoknux{~~<81><92><A1><AC><AB><AC><AE><A6><A1><9F><9F><A2><A8><A3><9A><93><92>
<92><8E><8E><93><97><9E><A7><AB><A5><9E><A4><AC><8E>uiijkjhijlnpsrqqurihgghijmpq
rtutps~<90><A1><A9><A4><9D><96><99><A1><AB><AF><AE><AF><B2><B5><AD><A8><A8><A8> 

The image file can be displayed using:

xsat -inp=img file.img

SEE ALSO


For further information about WXP, email technical-support@weather.unisys.com
Last updated by Dan Vietor on August 10, 1998