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Improving GPS accuracy

Posted by ionut on February 12, 2012 at 1:00pm

It seems there are methods to increase accuracy of the GPS location to cm using a reference station network.

Real Time Kinematic (RTK) satellite navigation is a technique used in land survey and in hydrographic survey based on the use of carrier phase measurements of the GPS, GLONASS and/or Galileo signals where a single reference station provides the real-time corrections, providing up to centimetre-level accuracy. When referring to GPS in particular, the system is also commonly referred to as Carrier-Phase Enhancement, CPGPS.

Check this link:

http://en.wikipedia.org/wiki/Real_Time_Kinematic

accuracy, gps

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Comments

ionut February 13, 2012 at 12:20pm

Colin-Great, but how are the base and rover going to communicate to each other.Rtklib is a Linux or Windows library, therefor you will need at least 2 computers and 2 usb connected uBlox receivers to have a minimal test platform.Also you will need some kind of wireless communication between these 2 computers.Right?
MarcS February 13, 2012 at 12:20pm

Did anybody try rtklib on a plane/Copter? Whats the accuracy? Does it work in high dynamics?

I think all solutions apart from "real RTK" using L1/L2 will provide resolution in the meter domain, especially in altitude... Which means for the part of flight where high accuracy is needed, the landing (or other stunts close to the ground :-), it´s still not good enough.

So for me there are two options: I got the money and buy RTK or I look for alternatives like optical, sonar, radar etc...
Colin Bouriquet February 13, 2012 at 11:56am

Here is the list : http://www.rtklib.com/rtklib_releasenote.htm

RTKLIB: Release Notes
Colin Bouriquet February 13, 2012 at 11:52am

ionut > yes it does, any uBlox or SkyTraq that can output pseudo-range and carrier phase will do the job... now the big difference will be on the antenna used and the baseline length... with a cheap antenna and short baseline you can achieve something really good over a short time period... of course with a survey geodetic grade antenna much better in much less time...
ionut February 13, 2012 at 11:52am

Simon, I don't think that library rtklib will work with cheap GPS receivers like uBlox.It will work only with the survey ones.Maybe Dave is closer to a practical DIY solution with DGPS.
Simon Wood February 13, 2012 at 10:01am

It's been mentioned here before several times.....

http://www.rtklib.com

Just add a couple of (cheapish) uBlox and SkyTraq receivers, or if your budget stretches to it a survey grade receiver such as Trimble, Novatel or TopCon you can get better performance. If you're really cheap some Garmin receivers can output raw data.

RTKLIB: An Open Source Program Package for GNSS Positioning
Dave February 13, 2012 at 5:56am

Yes, indeed DGPS is really the only practical option and LF beacons like these http://www.effective-solutions.co.uk/beacons.html would be a good idea..

Making a reference station is not that difficult, just record RINEX data over say 24hrs and compare that to a known OSGB reference station data (that is free - well the last time I looked) bingo, you have your site within a few cms.. this can be done with some Garmin GPS, I've done it with a Garmin Vista.
SaadT February 13, 2012 at 5:32am

The one you've mentioned requires special antenna and GPS receivers (those that are capable of tracking phase as well), which are more expensive (and heavier).
A better, lower cost option, in my opinion is Differential GPS (known as DGPS). It uses normal antenna, normal GPS receivers...only RTCM corrections are sent from the base to the mobile units over a data link. This gives accuracy of within a meter, which is reasonable in many situations. This is from my knowledge working as a seismic engineer,..we use both RTK and DGPS out here on the field.
I'm myself thinking of implementing a DGPS scheme myself. Basically i'll fix my base station and then generate and send corrections to the mobile unit. One problem here is that either i know my base station position very accurately OR i keep all positions relative. Lets see how it works.
Dave February 13, 2012 at 4:44am

Or this https://www.youtube.com/watch?v=FATVNEB1_BY ;-)
Dave February 13, 2012 at 4:42am

I think so. You could always make your own reference station...