Max2769: RTK GPS for all?

Here we go again.

Like mp3 encoders before LAME, RTK GPS based on inexpensive GPS receivers & software has long been a dream that no-one has been able to get working.

http://gpspp.sakura.ne.jp/rtklib/rtklib.htm

For years, a Japanese team has used a discontinued uBlox module that costs just as much as a commercial RTK GPS solution. Now the latest hobbyist movement is to use just the GPS front end & do all the baseband processing in software. Unfortunately, we have no idea what to do with baseband GPS data to convert it into RTK corrected information.

http://www.maxim-ic.com/datasheet/index.mvp/id/5241/t/do

For years, Maxim has had a GPS front end available for $11 but only now has anyone tried doing anything with it. http://unreasonablerocket.blogspot.com/2011/02/gps-progress.html

It doesn't look like he's going to have enough time to finish it.

There are some notes on using a laptop for baseband processing but no actual sourcecode.

http://www.maxim-ic.com/datasheet/index.mvp/id/5241/t/do#Application%20Notes

The only remaining step is really getting data into the format RTKLIB needs. This is really a movement worth getting behind, since RTK GPS would eliminate the pressure sensors, sonar, pitot tubes, & guesswork VTOL flyers have become familiar with. Well, unless you're in the business of selling pressure sensors, sonar, & pitot tubes.

For converting the baseband data to navigation solutions, there's fastgps: http://sourceforge.net/projects/fastgps/

Converting the baseband data to a format fastgps expects & linking fastgps to rtklib are the obvious missing pieces, but probably lawsuit bait.

Getting enough CPU power into an aircraft to process it is still cost prohibitive. The most economical solution is to use a $40 uBlox 5 on the aircraft & just run fastgps + rtklib on the ground, to generate DGPS corrections. That should give highly accurate 4Hz navigation. The problem is getting RTCM messages out of rtklib, & then fighting the lawsuits.

An RTK GPS system for under $100 is the kind of disruption that drew lawsuits from Fraunhoffer, in the 1990's, over mp3 encoders. Nobody wants to put any missing pieces in the libraries that might awaken Novatel or uBlox.

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Comments

wahaha686 April 11, 2011 at 12:35pm

For hardware, are there any dual frequency GPS RF front-end on the market?
Simon Wood April 11, 2011 at 11:34am

Remember that RTCM is just a compression scheme for the Psuedorange/Phase/other data, you could just as easily send uBlox binary protocol over a link (of sufficient bandwidth/reliability).

RTKLib does have a future feature of RTCM out... just needs to be coded ;-)
wahaha686 April 11, 2011 at 11:18am

@ Jack Crossfire

Could you explain why RTCM specifically would incite lawsuits?

My wild guess is that Novatel or uBlox has some patents on the process or technology.

Finding a LEGAL way to distribute such software to the open source community might be worth investigating. Just an optimist.
Jack Crossfire April 10, 2011 at 11:05pm

For converting the baseband data to navigation solutions, there's fastgps: http://sourceforge.net/projects/fastgps/

Converting the baseband data to a format fastgps expects & linking fastgps to rtklib are the obvious missing pieces, but probably lawsuit bait.

Getting enough CPU power into an aircraft to process it is still cost prohibitive. The most economical solution is to use a $40 uBlox 5 on the aircraft & just run fastgps + rtklib on the ground, to generate DGPS corrections. That should give highly accurate 4Hz navigation. The problem is getting RTCM messages out of rtklib, & then fighting the lawsuits.

An RTK GPS system for under $100 is the kind of disruption that drew lawsuits from Fraunhoffer, in the 1990's, over mp3 encoders. Nobody wants to put any missing pieces in the libraries that might awaken Novatel or uBlox.
wahaha686 April 10, 2011 at 10:38pm

I think Max2769 requires "Spot" Software (GPS baseband processing software), developed by Royal Philips Electronics.

The first page of the following PDF on Max2769 brings up the "Spot" Software
http://pdfserv.maxim-ic.com/en/ej/EJ63.pdf

The following article also mentions this "Spot" software
http://www.maxim-ic.com/company/press_room/product.cfm/id/1124

Anyone know how where we can download this software?
My Google search didn't turn up anything.
bcr February 23, 2011 at 9:04pm

"Eliminate" iff the weather is perfect and you're in a wide open space with no multipath. In reality, you'll still want to fuse this with traditional sensors.
hamish February 23, 2011 at 4:25pm

i like not depending on GPS for when my foamie makes it to mars :P
Simon Wood February 23, 2011 at 1:03pm

Having 'spoken' with Tomoji regarding the SDR GPS, this is intended for the 2.5.0 release. If you refer back to about October last year you will see that the SDR GPS will take a fair chunk of processing power.

RTK GPS is currently obtainable with the Ublox and SkyTraq receivers, and of course the much more expensive commercial/survey GPS.

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