Map Overlays

APRS now has a MAPS-OVERLAYS command which can overlay any type of temporary data onto the maps. Each time you execute the command, the data file is read, and the objects are overlayed on the currently displayed map. You have the option of adding these objects to your P-List, so that they will remain on your maps as you zoom and drive... Because of the large volume of potential data, only a few files (*) are provided with the distribution copy of APRS as follows:

*DIGIS.POS SHows all known APRS digis natiowide with range circles
*GATES.POS Shows all known gates
*FREQS.POS Shows all known APRS Frequencies
*NWSPOSNS.POS SHows all NWS sites
*STORES.POS Shows all nationally advertised Ham stores
2M-VOICE.POS Shows locations of wide area 2M voice repeaters
WRECKS.POS Shows all CAP known crash sites. Important for SAR so that time is not wasted on old wreckages. There are several files CRASHE, W, SE, M, C, NW and CA.POS
RSHACKS.POS Shows all Radio Shacks in the country
ZIPS.POS Shows all Postal Zip codes. Get ZIPS1, 2, 3..., 9.POS

Once you donwload these additonal files for your area, if you COPY just the file for your area to the generic filenames of RSHACKS, WRECKS and ZIPS, then you can see them from the menu directly with a single key stroke. Otherwise you will have to enter MAPS-OVERLAYS-OTHER-FILENAME to see them...

If someone decides to combine all the files into single files (on big and fast machines) please do not name the original source file with the generic name, or it may be overwritten by someone elses customized file of the same name. That is also why the first line comment line appears when you load a file. This is so you can see whats really in the generic filenames. Keeping the files small for your area really speeds things up on older slow disk drives...

THese files must be placed in your APRSPOS directory. You can make these POS files for your own area limited only by your imagination. A file of all VOICE repeaters is important for the traveler. Use the freq as the callsign so that it shows on the map. Or you can make a .POS file of all your club members so that you can visualize your net.

FORMAT: The format is simple. Each line consists of a NAME up to 9 characters (variable length) followed by the normal FIXED station APRS position format beginnning with an exclaimation point. You MUST also add a single line descriptive comment at the beginning that will be displayed to the user when he executes the OVERLAY command. If you omit this first line, then the first line of data will be used as the comment line and it will not be plotted... Have fun!

BUILDING FILES: THis is easy. Just use APRS. Use the INPUT-ADD command to add as many objects to the map as you want. When you are finished, do a FILE-SAVE. Then load the file into a text editor and delete all of the date/times between the end of the object name and the beginning of the latitude. Replace all this with just the exclaimation point (!). Then save the file as a .POS file in your .POS directory.

Do not worry about exact lat/longs. Just use your eyeball on the most detailed APRS map that you have. The exact location will never matter, since anyone who is viewing the overlay data will be using the SAME map to VIEW it as you did to estimate the position in the first place. As you get more detailed maps, or as someone visits the site with a GPS, then clearly the posits must be updated. But you can do that later...

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Mail comments/corrections on content to Bob Bruninga and on HTML formatting to Steve Dimse