[aprssig] APRS MileMark data base
bruninga at usna.edu
Sun Apr 13 08:59:21 CDT 2008
> WHat is this MILEMARK database you mention?
> What APRS clients support it? What...format?
It is MILEMARK.DAT that was distributed with APRSdos. I developed it manually over the years and evntually it covered most milemarks in most states int he USA. The original presentation method was that it would draw a vertical or horizontal line across the interstate to show where a requested mile mark was. Roger used my file to support a mile mark display in UIview as well.
The advantage of that file (since it was hand generated for every milemark in the USA) was that I only had to enter a LAT or a LONG for each point, instead of both, since you could find the mile mark by the intersection of the line with the road.
But after a few years, I expanded the APRSdos display to actually draw the milemarks on the map every 10, 5, 2 or 1 mile depending on what zoom scale you were on, so that you didnt have to enter a mile mark, just hit "MM" and it would overlay these milemarks on the map. THis made it much easier to place a non-APRS mobile on the map simply by cursor.
This was another big effort, since I had to go back through a manually enter the additional LAT or LONG at each point. This file was named MM-DATA.DAT Converting over to this new format was on Roger's list, when poor health overtook him and so it never got into UIview. But the original method is still there.
Again, it is VERY powerful, when combined with the fundamental APRS dead-reckoning. This lets an APRS operator maintain a track on non-APRS stations whenvever they report their position by mile mark. You just place them on that point, give them a speed of 65 MPH or so and the direction they are headed, and then their DR position will be updated every minute as they move down the road. Of course, the APRS client has to proplly distinguish these DR'ed objects from other ones. This was done by the symbol color atribute (CYAN), and an "anchor line" drawn back to the last reported position, indicated by a small "anchor circle".
Every DR'ed object on the map was updated every minuite. The length of this line gave a good indication of the amount of time that has passed since that position was last reported.
After 10 to 30 minutes if you hear the non-APRS operator again report his milemark, and if his DR track is too far off, you can click him, move him where he is now, and adjust his "speed" appropriately if needed...
In fact, his speed could be fixed automatically, but I never got around to it, siince it was so easy to do by click and drag.
APRS operators need to get into the mindset that their job at their ARPS display is mostly as INPUT-OPERATORS, inputting objects about everything going on in the event area right now. This is so that all APRS displays can present to everyone what is really going on.
If no one is inputing all the non-APRS objects in real time, then all you get is what we have.. a few APRS mobiles driving around... ho-hum. that is, APRS representing only about 5% of what is really going on in ham radio in that area...
The file is a text file, so it is very easy to use. Too bad many other clients have not included it. THough, I honelstly assumed that they would use much better data, from all of the GIS systems out there that cover so many more roads than just the interestates.
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