# The ULTIMATE GPS rocket locator

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#### plugger

##### Well-Known Member
So for years we've been talking GPS and how to best receive packets from your transmitter to tell you where your rocket is. Historically my GPS rocket tracking experiences have roughly followed this pattern.

1) receive packets from the GPS tracker/transmitter at a 1Hz frequency during descent.
2) lose radio line of sight at a few hundred feet AGL and no longer receive packets from the transmitter.
3) navigate to "last known good packet" location.
4) hope for an updated "final" on the ground packet OR continue the bearing I took to get the last known good packet location IF I don't receive another packet.
5) Hope I get that final packet that will tell me exactly where my rocket is whilst continuing the bearing.

As you can see the above process could easily be improved upon. Also, the higher you go the harder the above process is due to increased distances on the ground. So for a while now I've been wondering how we could improve our ability to get that final position packet. Boosting radio wattage on the transmitter COULD work but most likely the ground based interference would still absorb the RF and you'd drain your battery quicker. Improving your Line of Sight could help but I've never attempted to hoist my Yaesu VX-8GR on a tethered balloon or a quad copter. I'm not sure if I want too either. Cellular/mobile internet gateways COULD be of use BUT most likely where extreme altitude projects are launched there is little if any mobile data connections available.

This weekend the Outernet was brought to my attention and I assumed you might be able to integrate and APRS system to it. Sadly I was wrong. That said during the discussion I was pointed to one HELL of a unit called the RockBLOCK Mk2. Effectively it's a Iridium satellite modem. The units are $250 USD each from SparkFun. https://www.sparkfun.com/products/13745 I can't see any reason why a RockBLOCK Mk2 + Arduino Pro Mini (https://www.sparkfun.com/products/11113) + a uBlox 7 GPS chipset (https://www.sparkfun.com/products/13670) couldn't be leveraged to provide a GPS position reporting system that leverages the Iridium satellite network to provide an email every 10 minutes telling you EXACTLY where your rocket is regardless of location. The RockBLOCK Mk2 unit we'd want would most likely be the naked model with the SMA antenna connector to ensure the antenna has LoS to the sky regardless of final orientation of the unit on the ground. So my expectation is that the above process for locating a GPS position transmitting tracker would be as follows. 1) launch rocket and wait until it's back on the ground. 2) go to somewhere with mobile data network coverage (eg Bruno's in Gerlach) 3) drink frosty beverage whilst waiting for an email to arrive. 4) open email, finish beer, and plan excursion for rocket recovery in the comfort of a relaxed environment with no immediate urgency. You know where the rocket is within a meter or two so there's no real chance of losing it unless you can't get to it or someone steals it. The only negative of this solution is that you've got to purchase a data plan to get your once per 10 minute slot on the Iridium network. Cheapest cost is 45 pounds for 500 transmission units in a one month window. That should be more than enough for testing and usage. Comments? From what I can see this is a$300 USD solution (excluding power) that would allow us to find the final rocket location for extremely high altitude projects simply and accurately. Also, I do realise that BigRedBee has their SBD unit that seems to be a commercial version of this solution but I do suspect those units would be significantly more costly.

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#### bigredbee

##### Well-Known Member
Hopefully we'll do some testing using my version of the tracker you describe this weekend in an actual rocket flight. It's an Iridium 9602 with a u-blox 7 GPS, "Teensy" microcontroller, and some power conditioning circuitry. It all runs off of a single cell LiPo battery. The 9602 is nice in that it allows you to use a single antenna for both GPS reception of Iridium transmit / receive. The entire device is about 45mm square -- just much larger than the 9602 itself.

The normally used ceramic patch antennas are pretty directional, and don't perform well in all directions, especially if it were to land "face down". We're using a helical antenna (expensive -- antenna alone was > $100) inside the nosecone to avoid that problem. Preliminary testing shows it works well lying flat on the ground, as you would expect after landing under parachute. #### Adrian A ##### Sponsor TRF Sponsor TRF Lifetime Supporter So for years we've been talking GPS and how to best receive packets from your transmitter to tell you where your rocket is. Historically my GPS rocket tracking experiences have roughly followed this pattern. 1) receive packets from the GPS tracker/transmitter at a 1Hz frequency during descent. 2) lose radio line of sight at a few hundred feet AGL and no longer receive packets from the transmitter. 3) navigate to "last known good packet" location. 4) hope for an updated "final" on the ground packet OR continue the bearing I took to get the last known good packet location IF I don't receive another packet. 5) Hope I get that final packet that will tell me exactly where my rocket is whilst continuing the bearing. As you can see the above process could easily be improved upon. Also, the higher you go the harder the above process is due to increased distances on the ground. So for a while now I've been wondering how we could improve our ability to get that final position packet. Boosting radio wattage on the transmitter COULD work but most likely the ground based interference would still absorb the RF and you'd drain your battery quicker. Improving your Line of Sight could help but I've never attempted to hoist my Yaesu VX-8GR on a tethered balloon or a quad copter. I'm not sure if I want too either. Cellular/mobile internet gateways COULD be of use BUT most likely where extreme altitude projects are launched there is little if any mobile data connections available. This weekend the Outernet was brought to my attention and I assumed you might be able to integrate and APRS system to it. Sadly I was wrong. That said during the discussion I was pointed to one HELL of a unit called the RockBLOCK Mk2. Effectively it's a Iridium satellite modem. The units are$250 USD each from SparkFun.

https://www.sparkfun.com/products/13745

I can't see any reason why a RockBLOCK Mk2 + Arduino Pro Mini (https://www.sparkfun.com/products/11113) + a uBlox 7 GPS chipset (https://www.sparkfun.com/products/13670) couldn't be leveraged to provide a GPS position reporting system that leverages the Iridium satellite network to provide an email every 10 minutes telling you EXACTLY where your rocket is regardless of location. The RockBLOCK Mk2 unit we'd want would most likely be the naked model with the SMA antenna connector to ensure the antenna has LoS to the sky regardless of final orientation of the unit on the ground. So my expectation is that the above process for locating a GPS position transmitting tracker would be as follows.

1) launch rocket and wait until it's back on the ground.
2) go to somewhere with mobile data network coverage (eg Bruno's in Gerlach)
3) drink frosty beverage whilst waiting for an email to arrive.
4) open email, finish beer, and plan excursion for rocket recovery in the comfort of a relaxed environment with no immediate urgency. You know where the rocket is within a meter or two so there's no real chance of losing it unless you can't get to it or someone steals it.

The only negative of this solution is that you've got to purchase a data plan to get your once per 10 minute slot on the Iridium network. Cheapest cost is 45 pounds for 500 transmission units in a one month window. That should be more than enough for testing and usage.

Comments? From what I can see this is a $300 USD solution (excluding power) that would allow us to find the final rocket location for extremely high altitude projects simply and accurately. Also, I do realise that BigRedBee has their SBD unit that seems to be a commercial version of this solution but I do suspect those units would be significantly more costly. Glad to hear that Greg is working on his Iridium product. I have been tempted to go down that path myself. Instead I'm working on something that addresses the ability to get post-landing data in a smaller, less-expensive unit. The prototype hardware is mostly done but I'm slogging through the firmware. Hoping to do some testing at Balls this year. I'm going to try to avoid saying much more until we get some test flights in #### plugger ##### Well-Known Member Hopefully we'll do some testing using my version of the tracker you describe this weekend in an actual rocket flight. It's an Iridium 9602 with a u-blox 7 GPS, "Teensy" microcontroller, and some power conditioning circuitry. It all runs off of a single cell LiPo battery. The 9602 is nice in that it allows you to use a single antenna for both GPS reception of Iridium transmit / receive. The entire device is about 45mm square -- just much larger than the 9602 itself. The normally used ceramic patch antennas are pretty directional, and don't perform well in all directions, especially if it were to land "face down". We're using a helical antenna (expensive -- antenna alone was >$100) inside the nosecone to avoid that problem. Preliminary testing shows it works well lying flat on the ground, as you would expect after landing under parachute.
That's fantastic news Greg. Good luck with the testing! Would it be too much to ask that you let us know how the testing goes, either in a new Electronics thread or this one?

#### plugger

##### Well-Known Member
Glad to hear that Greg is working on his Iridium product. I have been tempted to go down that path myself. Instead I'm working on something that addresses the ability to get post-landing data in a smaller, less-expensive unit. The prototype hardware is mostly done but I'm slogging through the firmware. Hoping to do some testing at Balls this year. I'm going to try to avoid saying much more until we get some test flights in
I'm really quite curious about what you're going to bring to the table in the near future Adrian. Here's hoping your testing at Balls is successful!

#### ksaves2

Wow, Looks like tracking solutions are going to get a mite bit healthier on both ends of the spectrum. Economical
solutions for those on the lower end of the scale and increased reliabiity for very high flying projects that may drift
a fair distance from the launcher.
As long as the hardware is rock steady reliable, an Iridium based reporting system would be a heck of a lot easier than
setting up a "mesh" system with multiple ground receivers on the intended downrange path.
Bet something like this that you folks are planning would have been appreciated by Mr. Michealson with the
citizens to space project because if I recall correctly, it took awhile to find the booster. Ky probably would have had
an entertaining video of the rocket "phoning" him! Kurt

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#### plugger

##### Well-Known Member
Wow, Looks like tracking solutions are going to get a mite bit healthier on both ends of the spectrum. Economical
solutions for those on the lower end of the scale and increased reliabiity for very high flying projects that may drift
a fair distance from the launcher.
As long as the hardware is rock steady reliable, an Iridium based reporting system would be a heck of a lot easier than
setting up a "mesh" system with multiple ground receivers on the intended downrange path.
Bet something like this that you folks are planning would have been appreciated by Mr. Michealson with the
citizens to space project because if I recall correctly, it took awhile to find the booster. Ky probably would have had
an entertaining video of the rocket "phoning" him! Kurt
I agree Kurt, looks like tracking is going to see some good innovation in the near future. Exciting times. I'm really looking forward to the proposed SpaceX satellite Internet network, hopefully that will be rolled out on schedule. With that I suspect we'd be able to cut out Iridium and move over to SpaceX's offering which would provide a much higher bandwidth along with significant cost savings.