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Shotgun!
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Discussion Starter #1
So its a system that has been around for quite some time. But I am not up to speed with the real world limitations.

Could a APRS tracking unit be put in each car for an event and then monitored by organizers?
(from my understanding the signals from each car would bounce off the every other car (beacon) in range until it gets to a internet connected station.)

How many radios transmitting before everything gets plugged up with traffic? (could you have 40 or 50 radios?)

As long as it is not used for commercial purposes its legal? (as in the organizers of the event being non-profit. CARS is non-profit but RA is for profit)

How often can the radios be setup to transmit their position?
 

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Dramamine is for DramaQueens
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"The Micro-Trak RTG is a transmitter only, and may ocassionally send very short packets coincidentally with other transmitters."

Looks like it won't relay data.
 

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Most mobile trackers are not typically configured as "digi-peters" due to the fact that you can create a huge traffic crush in relatively short order.

An Example:
Car 1 Transmits and is able to be heard by 4 cars (2 ahead and 2 behind it)
If each of these cars is a digi-peter, then car 1's report is repeated by 4 other radios
Each of these 4 radios may be heard by 2-4 other radios each of which then also repeat the report of Car 1
etc....

Now you can control how many "layers" the repeating is done with the path of the packet, but if your goal is to use the cars to guarantee it reaches an uplink point, then the path would need to be long (Think Wide3-3 or worse)

The generally accepted method is to limit your packet paths to something like Wide1-1 or Wide2-1 to limit the number of repeats as it is the expectation that in most areas, you should be able to hit a high-power digi within 2 hops that will then get your traffic out to the larger area, or an i-gate which will port the traffic to the APRS-IS (Internet).

We have used APRS in several tests at our events in MN for purposes of tracking lead cars and sweep vehicles to try and cut down on some of the "housekeeping" traffic on the voice net. Typically it involves adding a second radio at Net Control to act as a receiver/digi-peter with a laptop attached and mapping software running. This gives the Net operators visibility into location of these course assets and also provides a way to repeat the traffic from a high-power antenna so it can be received by one of the local i-gates in the area. Our experience thus far has been that it is useful, but still intermittent due to the fact that it is a simplex system between the object being tracked and the Net station. There are places where the APRS packet may not get out to be received.

This could be remedied by installing a few more mobile digi setups, but as of right now, the quantity of APRS operating HAMs is still low, so hardware and operational skills are at a premium.

Brad
 

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Shotgun!
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Discussion Starter #7
Thanks for the reply Brad. Your answer is what I feared. :( You would almost have to have a APRS crew to ensure that the stage(s) are covered and that the tracking of the cars is covered. This= more volunteers and worst of all, very specific trained individuals. This then is not feasible for our application.

The search continues to find an economical (relatively) way of keeping track of cars on stages...
 

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pressing on tirelessly
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Kris Marciniak and I fiddled with this a couple of years ago at various events in the southwest. He built a number of inexpensive trackers to put in cars - a pelican box with an OpenTracker and an HT. I worked at it from the other side - I built several inexpensive digipeaters from 2m radios and TNC-X's. I deployed the digis at North Nevada Rally for a couple of years. They were about $200 ea, most of which was the antenna and the battery. (And I inadvertently drove up the price of certain 2m radios on Ebay for a few months.)

You get collisions, but it's not really that much of a problem. You need to make sure people have their settings right though, so they don't transmit too often, or with too high a WIDE setting so you get useless extra repeats. And don't let the cars digipeat, for the reasons mentioned above.

</rant on>The main reason I gave up on APRS is because I got frustrated with it. It offended my networking sensibilities. It's a really really really stupid protocol that was fine back in the 80s when it was invented, but really has no place in a modern world of auto-routing, self-repairing networks. I did build a digipeater board that plugs into a TNC-X with that uses OLSR, but it only ever got to the prototype stage.</rant off>
 

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Couple of random thoughts.
Is the goal to pinpoint where someone is on stage, or just that they are on a particular stage? Transponders as they exist would work in terms of who is on stage or not, but not pinpoint. Basic access control. automate timing to a certain extent.

If the goal is to pinpoint lost crews, would an avalanche beacon be usable tech? Something along the line of putting timer on it. Set it for x minutes before it broadcasts, so if you safely exit stage, you hit the reset or off button. If you are incapacitated, it starts to broadcast when the timer expires. Or it can be actively turned on if the crew capable of hitting the switch.
 

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Shotgun!
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Discussion Starter #10
The goal is to know where every car is at as close to real time as possible. From my days of avalanche beacons (please correct me if I am wrong or some new tech is available) they are a hide and seek kind of device that broadcasts a signal that can be tracked back to its source.
 

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Not knowing much of anything about networking or radio things. Could an app on a smartphone take advantage of GPS and broadcast that? Granted we are sometimes in the middle of nowhere, but my GPS always seems to still work. Could just take a bunch of old cheap phones with GPS built in and do something?

If I am talking out of my ass, carry on. :)
 

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That tech already exists via smartphones, but I think the cell technology is what will let you down in many of the remote locations that rally tends to be permitted. You'd also have to constantly power the phone, as the gps in most phones will exhaust the battery pretty quickly. I suppose you could get folks to join google latitude for those rallies in cellular coverage areas. That will triangulate from cell towers as well as use in phone gps. However, i suspect that isn't as elegant as the original poster is looking for.
 

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pressing on tirelessly
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Actually I don't think it's the GPS that kills the battery, it's having the display on. My android seems to be able to go for a couple of days with the GPS on, but lighting up the screen will kill in a few hours. That and searching for service.

But yeah, the problem with doing it with a smartphone is getting service.

Bryan, what exactly are you trying to do? What's the 2m coverage like in your area? Do you have someone that can drop off digipeaters? What kind of budget are you facing? APRS *does* work for this sort of thing.
 

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pressing on tirelessly
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Oh, and I'd like to point out that if you build/acquire trackers, you can issue them to non-hams as long as they don't change the settings. The trackers are considered remote transmitters under your control.

Well, here in the US anyway. Not sure about Canada, eh.
 

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No, your other left!
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Actually I don't think it's the GPS that kills the battery, it's having the display on. My android seems to be able to go for a couple of days with the GPS on, but lighting up the screen will kill in a few hours. That and searching for service.
The active type gps kills the battery. It's not always working even if its active though. So if you have GPS enabled but you don't have Google Maps open, it's not actively tracking the satellites.

Cell service is terrible. At STPR and NEFR this season, I could *barely* get texts out at service. Forget it on stage.
 

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Put the steering wheel back on
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In desert racing we use something called the IriTrack tracking system from International Racing Consultants. These trackers are mandatory in SCORE and Best In The Desert competition. The units operate via satellite and don't rely on the cellular networks, using GPS for location (collecting data every 5 seconds) and satellite phone communication to transfer the data (location and speed), which they relay to the event's IRC Control Center (and the internet) in two minute intervals. Additionally, the unit senses g forces and inclination. If it senses a high-g impact (over 5g) or a roll an alert goes off at the control center. The control center will then call the vehicle (unless it's still moving) via the IRC unit (it has a built in microphone and speaker) to ensure everyone in the vehicle is ok. They also sometimes call if the vehicle stops on course. In the open desert where the next competitor may not come along for another half hour or more and rescue is anywhere from 15 minutes to hours away this extra level of safety is definitely comforting. Unfortunately it isn't cheap, as the rental cost for one of these units is $275 per race. I don't think these would work for rally, but I think the concept is good. If there were a version with fewer bells and whistles and a rental cost below $100 (ideally $50 or less I'd say) I could see competitors going for it. Something like a Spot tracker would be great if it were possible to view all the trackers on a single map.

EDIT: I realized I thought I remembered seeing one of these in Antoine's car at 100 Acre this year so I went back and checked my photos. Sure enough he had one mounted on the fuel cell behind Nat. No idea if they ever ran it at another event.
 

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I looked into sat comms awhile back, and I suspect that the majority of that $275 price is just for that. Satellite bandwidth is spendy!

The rest of it is pretty straightforward. Good GPS chips can be gotten for about $30, and a 3-axis accelerometer is only a couple of bucks. A microcontroller (PIC or ATMEGA, etc) to talk to those, check for extreme cases, and compose data messages is only about $4. The tricky part is the comms.
 

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I looked into sat comms awhile back, and I suspect that the majority of that $275 price is just for that. Satellite bandwidth is spendy!
I suspect that satellite bandwidth may well be a significant part of the cost, but I am not sure it is as high a percentage of the cost as you might suspect. Stuff like vehicle ID, GPS position, heading & speed can likely be encoded into packet bursts of around 20 - 30 bytes. If you want the unit to transit very 2 mins, that's 30 packets per hour, so for a 24 hour race, just as an example, that's 24 hours * 30 packets * 30 bytes = ~ 20KB per competitor. I think the balance of the cost is the amortized cost of development of the system, amortized hardware cost of leasing the units for the race (& repairing broken or lost units), setting up & maintaining the back office servers to collect & process all the results, analyze results for each competitor to make sure they didn't deviate more than the allotted amount from the course, personnel to actively monitor system for triggered alarms e.g. high G impact detected by unit & call the competitor's vehicle to make sure they are okay, as well as trying to make a profit at the same time.
 

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I've been looking into using the CC1125 radio chip from Texas Instruments, paired with a cheap GPS module, RF amplifier and a microcontroller to create a tracking system running at a much higher update frequency than APRS. Like what has been said before, we can do so much better with modern tech in terms of receive sensitivity and bandwidth. I have started designing a prototype but haven't built it quite yet. At this point it looks like I could do a 5W 70cm transceiver with battery for maybe $160ish, and since the radio chip has a low-level interface I could built a custom protocol or try to integrate it into existing APRS systems. At this point I'm not sure if I can dump the money into it (college student) but I think it has potential to have a high enough sensitivity to still work in rally conditions. Certainly with a relay mesh system it could probably do even better than simplex.
If anyone has any suggestions, info, or interest in this, please feel free to contact me.
 
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