MARATHON.TXT MARATHONS AND APRS Document version: 8.3.5 10 Mar 99 Author(s): Bob Bruninga, WB4APR ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This file provides important notes about Field operation of APRS. The first part shows how even ONE station at NET control can provide a valuable service even with NO ONE ELSE on APRS! After that portion is some other lessons learned from the Marine Corps Marathon in 93 and 94. ONE-MAN APRS MARATHON USING DEAD RECKONING: All it takes is an APRS Display in front of the Voice NET operators. As long as they see the LEAD and TAIL runners and mabye the lead FEMALE and PACK, they can do their job well. But you can do this without even a TNC, Radio, or GPS as long as the race officials and Voice OPS can see these important ICONS moving along the map. Here's how to do it simply with only a laptop. Set the APRS operator off to the side with his laptop but its external display in front of the voice operators. He operates entirely from his own screen, placing the LEAD on the map with the correct course and a speed of 9 knots. The object magically moves along by dead reco=koning, and after the event proceeds for about 15 minutes, the TAIL is pretty well known and it too can be placed on the map with an initial speed of 6 knots. ALready the Voice Net operators can see the progress of the marathon. As the APRS operator overhears reports on the passage of the LEAD, or TAIL, the he simply uses the hook-INSert capability to update the positions of the main objects whenever the dead-reckoned objects stray from the course or are ahead or behind the predicted positions. If he is connected to a radio and TNC, then all other APRS stations within range can see the event too. The APRS operator still just sits in the corner with his laptop and LISTENS. Occassionally he may make brief announcemnts to the radio OPS, that the LEAD should be arrriving at.... or the TAIL should be passing.... etc.. but his job is to keep the display accurate. The POINT here is that sometimes we trip over our own high tech ambitions by trying to do TOO much and end up with nothing working. We now do our local marathon this way without any trackers. We didnt decide to do this marathon until 2 days before. ALthough 5 trackers actually showed up, this marathon is along a railroad bike trail where cars have no access, and even then CARS and TRACKERS are usually RARELY exactly where the LEAD and TAIL are, but seem to start and stop and wander around. On the otherhand the Dead-reckoned position of that LEAD object just keeps on trucking along at 9 knots, just like the runner that it represents. In my experience, the DR'ed object for the LEAD of a marathon will always work better than any other solution other than a helemet mounted tracker on the guy himself (which just will not happen). DETAILS AND LESSONS LEARNED. 1) The most important thing at net control is for the APRS station to transmit at extremely low power if at all so he does not QRM the voice ops. Set CONTROLS-XMT off. Use O-C-T to set your TNC DIGI OFF too. At one event, I used 100' of RG58 to further weaken my sigal and get it away from the OPS tent, but then put a beam on the end to get into the local digi. 2) If your event route is circuitous, and you do not have a good mind's eye for the 360 degrees of the compass, you may want to have some penciled in COURSE directions along major legs of the route. Also be familiar with the fact that the LEAD is moving .3 miles in 2 mins, and the tail is moving .3 miles in about 4 minutes. THink or make notes as to what these distances are on the 2, 1 and 0.5 mile map scales.. Depending on your map detail, at a one minute reporting rate, I found the 1 mile scale to be the most useful, providing a useful coverage for about a 10 minute period. 3) APRS DR's by the minute. But it only updates the screen when it XMTS or when the screen is re-drawn. WIth CONTROLS-XMT off, then you need to hit the space bar occassionally or set alt-S-OTHER-REDRAW to 60 minute or so automatically. 4) WHenever the OBJECT approaches a turn, hook his little anchor circle and move the cursor to his current position in the turn and hit INSert to give him a new COURSE. 5) Even on a straight-away, when you have time and he has moved a few minutes, hook his circle, and move the cursor to his current DR'd symbol location and INSert. Two reasons for this. FIrst, Remember that APRS is using a decaying timing period, so your updates to everyone on the net (if you were transmitting) are getting less and less frequent and since they only plot new positions when YOU transmit (unless they also have redraw on), you need to do this to keep their screens looking more alive. ALso, on your own screen it clears up the long DR lines and makes for a nicer display. These two steps 4, and 5, are where a good APRS talent really shines. Mess this up, and you will quickly lose the bubble and look real bad... This means that this APRS operator must have NO OTHER RESPONSIBILITIES. 6) One big problem is that with all the voice reports coming in of "first runner", some are in error or are confused. But since APRS is doing a good job of dead reckoning the positions, this can be used well to resolve confusing reports. The APRS LEAD symbol moving along at 9 knots never waivers in its progress. If we get a voice report that is more than a few hundred yards off from the DR'd report, NET control has learned to treat it with suspicion. In almost all cases, the APRS DR'd posit is right, and the observers at the check point were confused... and seeing the wrong runner.. 8) Understand Dead reckoning. As the race proceeds, drop the TAIL's speed to 5 and then eventually 4 knots. If you notice that your OBJECTS are running a little ahead or behind, especially the TAIL, then modify their speed. But the lead will always be 9 knots. At that speed, the lead is doing about 300 yards a minute. Even so, a 1 MPH error will still be within 100 yards even after 3 minutes! The Tail is much less predictable, so keep an eye on it closely. 9) Since the LEAD is done after 2.5 hrs, the rest of the day focuses on the TAIL as each check point is itching to close down, and is always asking where the TAIL is. Here is where the APRS operator can have a voice radio too, and can answer those questions direct without having to bother primary NET CONTROL. I am certainly not meaning to discourage having an APRS display at EVERY checkpoint, but recognize that if you do, the most important problem that you will have is QRM. THE BEST WAY TO DO ALL OF THIS, is to have RECEIVE only displays at NETCONTROL and all checkpoints. Then have the APRS operator 100 Yards away (or 5 miles away at home in his Shack). He LISTENS to all radio channels, and simply updates HIS display which in-turn updaes everyone elses. But he is TRANSMITTING from a distant location and causing NO QRM. ALso it is useful to have a separate APRS voice coordination net. The disadvantage of this is that you still need a GOOD APRS DISPLAY operator at the NETCONTROL, making sure that the big display is zoomed into to the focus of interest at any instant. The VOICE ops do not have time to move cursors and ZOOM. That is the APRS operators job. In that vein, use the MAP-SAVE to store up to 4 zoomed in maps in the HOT keys 3, 5, 7 and 9. I usually keep map 9 saved on the LEAD, and map 3 saved on the TAIL. Then I can save other focus areas in 5 and 7. In fact, the APRS operator can judge from hearing each voice communication what is the best map display to put infront of the operators. In fact, I was getting darn good! As soon as I heard the callsign of an incomming transmission, I would hit the appropriate hot-map so that the Voice operators just always had the "visual" on that guy's area as soon as he bagan speaking. WOW.. (this also had the benefit of forcing a map-redraw so that it was always current too). As the race proceeded, I was frequently re-saving new views in these hot-keys... to always present the best focus of interest. Do NOT think that you can just put up an un-attended display. It will look cute, but it will either be zoomed out too far so that you can see everything (all clutterd up) or zoomed in on the wrong area at the wrong time. PLAN ON HAVING A GOOD APRS OPERATOR DOING NOTHING BUT MANAGING the DISPLAY for NETCONTROL. Again, on race day, if you want to track STRATEGIC vehicles, water wagons food trains, VIPs, downed runners, pickup vehicles , etc.. even without GPS, just have an APRS operator (Anywhere, even at HOME) listening to voice freqs and UPDATING these objects. This can really spread out the work load. If you have more APRS volunters, assign each one a different net to "listen too" and to keep HIS objects current. This lets all APRS stations "on-site" operate in RECEIVE only for 0 QRM, but still show where everything is... on ALL displays.. MARINE CORPS MARATHON 1993,4 & 5: 1995: Had fewer GPS trackers and relied almost entirely on the DReckoning in APRSDR.EXE to move the LEAD, PACK and TAIL 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, (this is in contrast to actual GPS vehicles which often cannot follow everywhere that a runner can go. We also DR'ed the lead Handicapped, Woman, Special-Olympics and PACK. See DR.txt. MASTER-SLAVE. This year we also operated three AT-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! 14,000 runners, LOTS of hams, and our second year with APRS! In 93 we put 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: * Completely "sealed" GPS/TNC/Radio boxes should have drain holes! * 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. SUMMARY OF 1993 MARATHON! REPLAY MARATHON.hst to see how it went. To make sense out of it all, try playing back only one mobile at a time, and turning Callsigns off. WB4APR-9 was the lead Handicapped vehicle (started 15 minutes early, W3ADO-9 was the lead runner, and MOBILE-9 was the Tail. 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 transmitted. We counted about 115 in the file. (many could have been filtered out by APRS as duplicates). The result computes to almost an 80% success rate!