Comments on: Using Radiosondes as cheap GPS trackers

By: Dave

Dave — Thu, 22 Jan 2009 23:40:35 +0000

I dont know if anyone is stilla ctive here, but did anyone ever get this worked out?

http://www.getstock.co.uk

By: Dan

Dan — Sun, 16 Jul 2006 04:52:28 +0000

Possible application – tracking ground movement relative to a stationary benchmark. This could be useful to scientists remotely tracking glacial movement, seismic displacement near volcanoes and fault lines, etc. The shift in coordinates could be recorded at a central unit on the benchmark, and remotely phoned in once a day. I know nothing about what systems are already out there, or how to put the whole thing together – I bow to your collective expertise. It seemed like a good idea.

By: Wim Ton

Wim Ton — Wed, 12 Jul 2006 22:59:53 +0000

I have some of these sondes. The GPS is send as a satelite number + AFAIK a 24 bit velocity, not that difficult to see on a protocol analyser. So I guess to use the signal, one uses a stationary reference receiver and an ephemeris, to see where the various satelites are. Then integrate the speed to find the position. The LORAN sondes seem to modulate the raw LORAN signal on the 403 MHz carrier (what I saw on an oscilloscope) I picked up 24 of these on eBay for about

By: Nick

Nick — Mon, 10 Jul 2006 20:27:16 +0000

Thanks for all the comments / suggestions, looks like there is actually a relatively simple solution to the problem (although I have not currently managed to get it working).

Follow-up article is now available at: http://www.digitaldawgpound.org/nick84/post=133

By: obm

obm — Fri, 07 Jul 2006 15:45:31 +0000

Ok, since I do not have that device (the first I have heard of) and the protocol it uses, following will be purely theoratical (exactly what I do for living!):

You can use convolution theorem to obtain particular speed relative to the sender sattelite if you can overlap the incoming signals at different times, if you have exactly the differentiation at a specific interval, the process is even easier. Convolotion programs are cheap cpu-wise and source code can be found for example in numerical recipes in c. Then what you need to do is have a lock on at least 3 different sattelites and triangulate your coordinates using simple vector texel geometry. This is also very cheap. If you want error correction
then you can connect one or more sattelites depending on your algorithm. If you do not want complicated electronics, all these steps can be done using analog components (ever heard of analog computers?)

The problem is decoding of the signal I guess.
Is there a possiblity that the outcoming signal is analog or some ADC data?

By: Andres herrera

Andres herrera — Tue, 04 Jul 2006 18:20:38 +0000

hi, nice post, i will try, get a aerosonde on ebay, im developing a u.a.v system, but i use a expensive maxstream to get the telemetry data, maybe it could be sheapest :) .

Andres Herrera.

By: Taylor Alexander

Taylor Alexander — Tue, 04 Jul 2006 08:16:07 +0000

the best cell phone GPS solution is mologogo: http://www.engadget.com/2005/10/11/mologogo-adds-tracking-to-any-nextel-gps-phone/
it uses nextel phones, because most (all?) nextel phones have real, actual gps chipsets in them, and you can get their location without using minutes.
last i heard it had a good following, and they had developed the software pretty well.
-Taylor

By: Michael Dwyer

Michael Dwyer — Tue, 04 Jul 2006 03:02:23 +0000

My understanding is that the CDMA cell phones don’t have full GPS receivers in them, either. They simply transmit the doppler measurements to the network, and the NETWORK does all the hard work of figuring out what location a doppler reading corresponds to.

This is good because the network is a lot more powerful than your phone, so can get a location from a single reading, instead of taking a number of minutes to get an initial fix — an advantage for a battery-limited device.

So anyway, cell phone GPS might be a good avenue to explore after all…

By: Standard Mischief

Standard Mischief — Tue, 04 Jul 2006 00:08:11 +0000

{bold]
E911 != GPS
[/bold]

There are a number of cell phones out there that have real, true to life, honest to god, GPS receivers inside of them. Here’s one press release from March 2001:

http://www.forbes.com/2001/03/28/0328tentech.html

not all E-911 phones use GPS, (some triangulate off of cell towers), but some do.

Again, the GPS receiver is connected to the microprocessor, which is connected to a radio transmitter. All you would need is a firmware upgrade.

By: Botty

Botty — Mon, 03 Jul 2006 22:23:52 +0000

This may not be all that helpful, however, if someone does manage to figure out how to interpret the signal, perhaps with a computer, I’d recommend conscidering an fpga for the actual processing.

Fpgas can do things in parralel, making up for their mediocre speed. Decryption, analysis, perhaps involving FFT on a binary stream (you have to have an A-D converter) are all very parralizable. You can have the fpga manage stuff like position smoothing and deltas through doplar and such.

Fpgas are also rather low power.

Anyway, good luck!

By: danger mouse

danger mouse — Mon, 03 Jul 2006 16:26:34 +0000

@Standard Mischief:

E911 != GPS

On CDMA phones it might be possible, I would like to see a hack to get the A-GPS information out of them.

By: OrbnLgnd

OrbnLgnd — Mon, 03 Jul 2006 14:08:29 +0000

If the sonde is the one mentioned from Sippican, then right there on the data sheet most of the information needed is presented to fetch the data. Now, calculations.. another story.
He has the radio reception, but he mentioned hoping there would be a chip that would decode the audio.. well.. not so much a chip as an OLD MODEM. Certainly some hacking would be needed on the modem, but 400 baud digital biphase over an audio circuit is about as simple as it gets for an old telephone modem! The audio from the receiver should couple straight in? All my knowledge of radio systems is theory and no practice so I could be way off here.

And.. if all he wants is the GPS itself, then that talks to the micro that puts everything out over radio by RS232 (again, stated right there in the datasheet).

By: mentor

mentor — Mon, 03 Jul 2006 00:48:47 +0000

hi,

By: furtim

furtim — Sun, 02 Jul 2006 23:50:54 +0000

You can find formulas on the web for calculating location from the doppler signals. The math is fairly hairy, though. On the other hand, that sondemonitor program, for one, will do the math for you. There’s bound to be some other GPS calculating software out there.

By: Standard Mischief

Standard Mischief — Sun, 02 Jul 2006 23:33:57 +0000

sed ‘s/powered/controlled’