I'm thinking about building a gps system for a tractor. The gps receiver can be placed on the roof of the tractor to minimize interference. Regular GPS receivers are accurate upto "a few meters". (https://www.adafruit.com/products/746) I found you can correct your position with a base station. (RTK)

I have seen the Starfire gps receiver getting a good precision (a few cm i think) without basestation. I wonder how they work.

Are there other ways to get a more accurate position?

  • \$\begingroup\$ You're not going to get that kind of accuracy without local augmentation. \$\endgroup\$ – Matt Young Apr 8 '16 at 18:37
  • \$\begingroup\$ Is there free gps correction data on the internet? \$\endgroup\$ – MatMis Apr 8 '16 at 18:39
  • \$\begingroup\$ With CPGPS and DGPS (not exactly something you can buy from your corner store), you ought to able to get within 40cm. However, DGPS requires a beacon, which may not be feasible. Data fusion with an IMU (and possibly additional ground truth) is the typical solution. \$\endgroup\$ – uint128_t Apr 8 '16 at 19:00
  • \$\begingroup\$ Sub-metre accuracy is possible without a nearby reference station, using a PPP receiver. You need to sit still and average your position for several days for best results... \$\endgroup\$ – tomnexus Apr 8 '16 at 21:45
  • \$\begingroup\$ for that kind of accuracy, you would basically have to invent and launch your own constellation and supplement with ground stations, and/or just build your own ground stations and receivers. but that takes the g out of gps as it wont be global. it would be an LPS <grin> local positioning system. anything more accurate than the current gps is a local solution. \$\endgroup\$ – old_timer Apr 9 '16 at 2:37

There are few commercial products designed to do exactly what you are planning. They usually use RTK, with a known local reference station, up to 30km radius, and rovers installed on the tractors. Correction data is transferred via cellular or local ISM band radio. Multi constellation (GPS + GLONASS etc) receivers can provide improved performance even without RTK, but not to sub meter precision. And, since you don't have access to mil spec receivers, that option is also moot.

  • \$\begingroup\$ What do you mean with "mil" spec receivers? \$\endgroup\$ – MatMis Apr 8 '16 at 19:22
  • \$\begingroup\$ @matmis a military GPS has access to their higher precision signals, which are encrypted. Also, they have a second frequency band, only available as an encrypted signal, which allows them to remove the effect of the ionosphere. \$\endgroup\$ – tomnexus Apr 8 '16 at 21:40
  • \$\begingroup\$ many years ago they stopped mangling the gps results to allow military gps to be more accurate than commercial. granted I think the new constellation is finally going up (just in time!), and other or at least one other is putting their own up. no doubt the american one will again have miltary vs commercial accuracy for the new constellation (part of why it has taken so long, getting the air force and navy to agree on features and protocols) \$\endgroup\$ – old_timer Apr 9 '16 at 2:35
  • \$\begingroup\$ They stopped adding noise to the civilian signal, the military signal remained the same. \$\endgroup\$ – Lior Bilia Apr 9 '16 at 5:56

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