[aprssig] 20th century radio (was: APRS MileMark data base)

Stephen H. Smith wa8lmf2 at aol.com
Thu Apr 17 18:13:50 EDT 2008

Pentti Gronlund wrote:
> Ehhh...what exactly are these mile marks? We have streets and
> street numbers here in EU.
> 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 either, it would be good for both of us to do
> a little of travelling instead of dry specification work :)
> Benjamin OH3BK

In the U.S. the major cross-country highways known as the Interstate 
Highway System (high-speed 4-lane or more divided highways similar to 
autobahns) have a serially-numbered marker along the side of the road 
each mile. 

Normally these start at zero at the western end of (approximately) 
east-west routes and at the southern end of north-south routes.   The 
value counts up to a maximum value at the other end.   On routes that 
cross several states, the counter resets each time you cross a state 
line into a new state.    Interstate highway exit ramps are often 
identified on signs and on maps by the mile-marker number they are 
closest to.   More recently, these mile marks show on many car 
navigation GPS devices; they show prominently on my Garmin Nuvi 680 
mapping GPS.

One of the first mass high-profile uses of the mile markers was in the 
1970s when long-haul truckers starting using them to report the location 
of highway police over the then-new  CB radios. 

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.    Entering a mile mark number into the APRS 
apps that suport this then interpolates where that mile approximately is. 


Stephen H. Smith    wa8lmf (at) aol.com
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