The DES File

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This chapter is an abbreviated form of Robin's explanations, found under "Description of GPSS Maps - DES files" on the GPSS pages for adding maps.

Files with the .DES extension tell GPSS the geographical basics of each of the maps, including the file that holds the bitmap and the locations of NW and SE indexing sites on those bitmaps.

The DES file contains

pretty name the map file location 1 or type location 2 location 3 WAW file

pretty name is the name of the map that shows up in message bars and dialogs

the map file is the name of the BMP or VEC file containing the screen picture of the map

location 1, or type - for latitude/longitude maps, contains the type

for UK grid maps, contains an initial southwest calibration point

location 2 for most maps contains the southwest calibration point

for UK grid maps, contains the northwest calibration point

location 3 for most maps contains the northwest calibration point

for UK grid maps, contains the southeast calibration point

WAW file is the name of the related Where are We file

Examples
Here's the one for the UK area:

Line in File         Explanation

UK Area            The "pretty name" - how the map's name displays in menus, etc.

UKA            The bitmap file (UKA.BMP)

LL, 0, 0            Type (LL = lat/long) and size (0,0 = 640,480; can be 800,600)

500000N0100000W, 48, 404      Southwest calibration point, pixel X, pixel Y

550000N0100000E, 590, 176   Northeast calibration point, pixel X, pixel Y

GPSS.WAW         Related Where are We file

Pixel X = horizontal position in screen pixels, where 0 = far left

Pixel Y = vertical position in screen pixels, where 0 = top

Here's one for the Ascot area:

Line in File         Explanation

Ascot            The "pretty name" - how the map's name displays in menus, etc.

ascot            The bitmap file (ascot.bmp)

SU9066, 28 , 399          Southwest calibration point, pixel X, pixel Y

SU9069, 28 , 100          Northwest calibration point, pixel X, pixel Y

SU9666, 628 , 400          Southeast calibration point, pixel X, pixel Y

[blank]            Blank = use GPSS.WAW

The use of 3 calibration points is an artifact of GPSS's early days, when the thought was that maps would have to be rotated. Robin later dropped this concept, opting to give the 3rd line of the DES file an alternate use, the type and size descriptions (as seen in the UK Area DES file, above).

Finally, an example of the most recent type for vector maps:

Line in File         Explanation

USA 2 Mile            The "pretty name" - how the map's name displays in menus, etc.

USA2MILE            The vector file (USA2MILE.VEC)

VEC,3.24,0            Type (VEC = vector), left-right in kilometers

100000N1750000W, 0, 479      Southwest limit of the scale, pixel X, pixel Y

800000N0450000W, 639, 0      Northeast limit of the scale, pixel X, pixel Y

C0503_V1200_W0101_S0114_T0108-R0508_R0312_H1008_H0711_H0108_R1000$H1000$

In this type, the final line is shorthand that gives GPSS instructions for plotting. For more detail on this, follow the link in the first sentence of this chapter.

By Dave Gehman
© Copyright 2004, Robin Lovelock
Send changes, suggestions to Dave Gehman