[aprssig] 20th century radio (was: APRS MileMark data base)
bruninga at usna.edu
Thu Apr 17 19:48:32 CDT 2008
>> Bob, I think you have a too narrow perspective
>> with these mile markers and other odd proposals
>> of yours. I've never been to _North_ America...
> In the U.S. the major cross-country highways
> known as the Interstates have a serially-numbered
> marker along the side of the road each mile.
Actually, because of their value, almost all states now have
markers every 0.1 mile. This places a marker in view of ANY
stranded person within 250 feet. And gives him a coordinate
system to report his postion to the nearest 250 feet anywhere
along an interstate that can be 700 miles long (California).
This is as good as GPS (with SA on) and requires abslutely
nothing of the traveler.
> The database in question for APRS is a list containing
> the lat/long coordinates of the beginning, mid-point
> and end of the Interstate segments in each state.
Actually, it is just the ends of every more or less straight
line segment of every road. Some interstates take dozens of
segments, others take only a few.
And all 7,350 data fields was manually entered by me over years
of manually gathering data points from maps, overpasses, exit
numbers and so on...
I don't think you should trivialize that effort, since back in
1995, it allowed APRSdos operators to pinpoint any ham radio
interstate traveler to the nearest 250 feet or so anywhere in
the 4,500,000 square miles of the USA. Just as good as GPS
It is still useful for pinpointing the 99.99% of interstate
travelers that don't have APRS.... (99.8% are not hams, and only
5% of hams use APRS).
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