Guy's I've been long interested in running an experiment using the GPS Front End form a radiosonde to get real-time speed and position data. Here is a teardown of one of these sondes
The reason I got so interested in these is the software program Sondemonitor http://www.coaa.co.uk/sondemonitor.htm With this software and a typical radio scanner you can process the data from these sonde's in realtime.
What I find really interesting is the simple GPS Front End used in these sonde's
There are several DIY GPS receivers that are extremely cool (and difficult) I have a great deal of respect for the guy's that where able to do this. http://www.holmea.demon.co.uk/GPS/Main.htm
This one is a more modern version of the original done by http://lea.hamradio.si/~s53mv/navsats/theory.html
My goal here is to use the radiosonde front-end and using a raspberry pi or VR Nuron along with an algorithm similar to the Sondemonitor program to get realtime GPS position and speed from the "Doppler Measurements" that the sonde's collect.
I know that the Sonde's use SPI interface so I've ordered a Bus Pirate to help out along with the new 200Mhz DSO we just bought.
If there is any interested in helping with this project please comment!
Sondemonitor uses ephemeris data from the internet and the doppler measurements from the sonde's to get the fix and what we need is an algorithm to streamline the process.
Wow that's very interesting project ... but for develop this kind of app is not possible to use SDR application ? I see that with this kind of new technology is possible to develop a lot of application .
Yes! It is indeed possible to use SDR and I have a TV dongle to use for experiments if anyone is interested in that type of experiment. BUT! It requires a great deal of processing to do realtime positioning in software with it. Right now it can be done with high-end video cards (GPU's) but we don't have that kind of processing power on our UAV's :)
I have another project to record the raw signal (not the raw GPS data) and post process it that can be done after the fact and get very precise data.
But this project is to use only the Doppler measurements provided by the radiosonde's front-end which is very much like a (Half-GPS) this allows a 2 Hz position fix if prior to launch you provide the software with ephemeris data (obtained from the internet) a description from the manufacture