On Tue, Jan 25, 2011 at 11:19 PM, <si...@mungewell.org> wrote: > >> Didn't Clinton turn the encryption off some >> of the accuracy bits of the GPS signal at some stage (making military vs >> consumer less important)? > > Yes SA was turned off. This is where 'they' deliberately added a random > offset to the position, so that it would 'confuse' consumer grade > receivers. Another arm of the US government then spent a lot of money > setting up reference stations (DPGS) so that this 'error' could be > correct. ... > The survey grade equipment will be using dual frequency receivers, where > the L2 frequency helps the receiver compensate for atmosphere conditions. > A dual frequency receiver will be able to average a position to get 1cm > accurate positioning. > > Usually in surveying you will tie everything back to a known point using > too receivers and just measure as the deltas from this point. Rover > measurements can be done with Real Time Kinetic (data link between base > and rover) or post-processed (work with files after the fact).
I was under the impression that you still need those reference stations for doing surveys, because of those atmospheric conditions you mention. _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
