I looked over and over again at some of the products that I saw online. None were meeting my needs.
So this is how I made my decision:
Need: I need a GPS tracker to retrieve the Payload
Optional Bonus: Working above 60K ft ASL would allow me to:
- Follow it in real time
- Record the Flight Path and Max Altitude Reached
Facts:
What if the payload lands in a zone without signal coverage?
- I cannot trust GSM.
Why using GSM in the first place?
- Because it’s way cheaper than any other technology.
Does it work above 60K ASL?
- The GSM transmissions won’t work above a couple of miles high but it doesn’t mean that the GPS of the phone will stop working.
(Additionally It’s illegal to operate a cell phone in the air)
Will the phone be able to record the flight path and altitude?
- That’s the great unknown. Some people claim it did.
I am skeptical but have no other solution.
What if the phone dies (bug, cold, battery, hard landing, …)?
- I want a backup system that doesn’t use GSM.
Why not using only the backup system then?
- Because it’s the most critical feature of the payload. For my first flight, I must have a backup tracking solution.
Will the backup system work above 60K ASL?
- Ideally yes, but I haven’t found one able to do it so far.
It only needs to work once the payload has landed.
Conclusion:
I need two autonomous and independent tracking systems. Each system must have its own power source, GPS and a different communication technology.
Primary system: GPS Phone + Battery Charger + External Antenna (optional)
Backup system: SPOT personal tracker + Track Progress
Details:
An Apple Iphone/Google Nexus One would be a first but they don’t meet the environmental requirements. The GPS Phone can be any GPS Phone that can be powered by lithium batteries. Most people have used the Motorola i290. Activated with Max Cache Size, it seems possible to record the whole flight path.
I will use the SPOT personal tracker for 4 reasons:
- It uses Globalstar’s communication satellites, it’s not limited by cellular coverage;
- It works under tough operative conditions (-45C, shockproof, waterproof, floating)
- It uses lithium batteries
- I can personally reuse this device for my next adventure.
Both devices should be trackable online through instamapper and spotadventures.
Total Cost: $300
Next: The Camera and Stabilization System!
What’s up with this project?
Sorry I got busy lately but my project is still moving forward.
More to come soon. Thanks for the follow-up!
Phones can indeed record flight path and altitude, but beware of the 60k problem – and also of the fact that phone GPSes are tailored to ground operations. We used an Android phone (G1) which refused to believe that we were climbing as fast as we actually were, so the track shows periodic 1500 foot jumps as it gives up on “smoothing” the track and starts again from the real altitude.
However, you’ll be glad to hear that the phone reacquires GPS when dropping below 60k feet and continues to work fine – we wrote software that would send position reports via SMS, which we’ll be putting in the Market.
http://dichro.blogspot.com/2010/02/declaring-weeks-advance-notice-of.html for the story.
Hi Mikolaj,
My roommate actually forwarded me your story a couple of days ago!
Thanks for your message and congratulations on your launch!
I have a couple of questions for you that would greatly help:
-Did your G1 logged some GPS locations above 60K ASL?
If so, I believe that it couldn’t send them through the GSM network at such an altitude. Did you manage to store them to get the Max Altitude?
If not, How did you determine the Max Altitude reached?
-What APRS Beacon, Radio did you use and how did you link it to the G1 GPS?
-Did you figure out what went wrong with it?
I am looking forward to hearing your feedback.
Thanks again.
The G1’s GPS stopped delivering valid data above 60k feet (just returned 0s for lat/long/alt), but we lost wireless signal a long, long time before that – it looks like we only had wireless signal for about 2000 feet above ground level.
Our APRS gear came from argentdata.com – we had a (separate) Garmin GPS, OpenTracker+ and PX-777 radio. The G1 was a standalone unit; we had no connection between it and the APRS gear. And it looks like we just screwed up antenna mounting and were radiating with the wrong polarization – mount your antenna vertically instead of horizontally and your chances of success will be much higher
Mikolaj,
Thanks for your answer! Your explanation with the G1 makes sense. Not knowing much about APRS, I am a little bit uncomfortable going into this technology. Connecting the GPS to the APRS beacon doesn’t look too hard, I still need to program it though (but that sounds doable).
However getting a call sign, finding a correct radio and setting the whole thing to get data through VHF sounds a little overwhelming. I just had a glimpse at the PX-777 radio and I have no idea how to get the data out of it.
The whole system is cheap though and with a 5MW radio, I should have no problem following the balloon … (if it actually works).
I may use your solution with SPOT messenger as a backup tracking device.