MARATHON.txt 7.4 APRS at the Marine Corps Marathon 1993,4 & 5 1995: This year we had fewer GPS trackers and relied almost entirely on the Dead Reckoning features in APRSDR.EXE. This program can dead reckon objects along the marathon route without operator intervention except when needed to correct for long term drift between the runner and the Dead Reckoned object. The LEAD runner goes about 9 Knots and the Tail goes about 4 Knots. Also, these tracks DO follow the exact course, where GPS vehicles often do NOT reflect the real path of the runner (where vehicles are not allowed). We also DR'ed the lead Handicapped, Woman, Special-Olympics and PACK. See DR.txt. MASTER-SLAVE. This year we also operated three 486 color laptops and two larger VGA displays all connected to the single APRS TNC. Only one laptop was operated by the APRS operator as MASTER, and all other laptops were placed in SLAVE mode in front of the other voice net controllers, so they could independently zoom in to areas of their immediate interest. If we had had more VGA monitors, each laptop could have also driven an extra large display. The small size of the laptops fit unobtrusively at the operating positions. See OPS.txt. APRS LESSONS LEARNED @ MC Marathon, 1994! Its over! 14,000 runners, LOTS of hams, and our second year with APRS! Last year we had GPS on the LEAD, LEAD Handicapped, & TAIL chase cars. It was great, but predictible. This year we let APRS dead-reckon the predictible movements of the chase cars and built 11 Trackers for the ambulances. Lessons learned: * Completely "sealed" GPS/TNC/Radio boxes should have drain holes in bottom! * Maritime GPS units withstand immersion in water. TNC's don't * You can't duct-tape GPS trackers to vehicles in the pouring rain * New Marine Corps Tents (made by lowest bidder) leaked everywhere! * 14,000 runners, vehicles, etc + RAIN = MUD * Mag-mount GPS trackers wont stick to aluminum HUM-VEES. * Tracking ambulances, which are parked for 99% of the event is BORING! * Ambulances with emergencies are under such close control by the ambulance direction net control, that he knows EXACTLY where they are anyway. Of 11 units, 2 never quite got finished, one just couldn't be attached in the rain, one leaked, flooded and died, the tinyest (running on AA cells) lasted 6 hours. It rained from 5 AM until 1400. Now for the good news: + We got double milage out of most APRS mobiles. They put their GPS's in stand alone trackers for the ambulances, but kept their LAPTOPS and used the INPUT-MY command to manually report their position. + The alt-SETUP-MODES-sPecial command let the entire event operate on 145.79 while ignoring ALL other non-participating stations. THis keeps all APRS pages free of non-participants. Many stand-alone trackers are XTAL controlled, so you MUST plan on using the normal APRS freq for special events. CONCLUSIONS: Next year, we will probably go back to tracking the high-profile chase vehicles and HAM mobiles that are always moving, rather than ambulances. These 11 trackers now are permanent HAM radio assets in our community in addition to the other 6 HAM mobiles that are permanently configured for APRS. SUMMARY OF 1993 MARATHON! The complete event can be re-played from MARATHON.hst to see how it went. To make sense out of it all, play back only one mobile at a time, and turn Callsigns off. WB4APR-9 was the lead Handicapped vehicle (started 15 minutes or so before all runners), W3ADO-9 was the lead runner, and MOBILE-9 was Tail-end-Charlie. Statistically, we did very well. W3ADO-9 was turned on at 0827 but did not move until 0902. It was removed from the vehicle at about 1127. Transmitting at once a minute, there should have been 145 posits trans- mitted. We counted about 115 in the file. The missing packets could have been either colisions, or bad GPS fixes (masked by buildings) so that the same posit was transmitted more than once (and therefore filtered out as a dupe by APRS). The result computes to almost an 80% success rate!