With DGPS we get about +-10cm for our non-military robotics project. So this isn't really true. We use a paid subscription but the free WAAS signal brings the accuracy to about +- 1m which is already pretty friggin good.
I wonder what justified this (probably expensive) upgrade?
It took me a while to find out why they are more accurate, I eventually found this quote: Greater accuracy is a product of advanced atomic clocks in the new satellites, Torok said. I think it's safe to safe that tiny atomic clock technology advanced in the decade between the existing satellites and this round.
They added a new military signal, presumably jam resistant. (It has a "spotlight" antenna that can provide a 100 times more power to a fighting theater. I'll see your alibab.com gps jammer and raise you 20dB…)
They also added another civilian signal (L5 - safety of life) which presumably has a purpose, but darned if I can find it. Probably related to different frequency, more power, different coding, something about the ionosphere… my guess is that it won't crap out at the same time the other one does from interference.
Some states, like Iowa (http://www.iowadot.gov/rtn/), also have real time information you can access to reduce the margin of error.
True RTK + IMU positioning systems will get you 1-2 cm 95% of the time (see Applanix, Novatel).
Omnistar refers to the HP accuracy as "real-time"[1] and:
> [it] will usually have a 2-sigma (95%) horizontal error of about 6 centimeters and a 99% horizontal error of less than 10 centimeters
Do you happen to know what kind of movement this is based on? For example, if it was attached to an RC car (assuming that the equipment is this compact, it may not be?) would you still be able to get this level of precision? Or is it designed for more consistent movement patterns?
OmniSTAR in particular and DGPS in general will operate under assumption that errors due to ionospheric and tropospheric effects change slowly in time and space. If this assumption is correct, then dynamics of the vehicle won't affect the corrections themselves.
My point with all this is that 99% of the corrected GPS solution should theoretically be within x cm of some point on the true path of the vehicle no matter how it moves in a plane. The question is, if you're interested in real-time solution, how far will the vehicle be from that point by the time you get this fix, and if you're interested in capturing vehicle's travel, how well will the curve fit through these points match the true vehicle path.
Also the error grows with distance. So if your bot is navigating off of objects 200 meters away, yeah you'll be more off. But you can use points closer to it and you'll get better results. Look around and you'll see that the velodyne has been made to work. Nobody loves it though.
The riegl has very low beam divergence, is beautiful, survey accurate, not waterproof and $300k+.
Don't forget the workhorse SICK scanners. They are cheap and have their pros and cons.