> 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. At present SA is set to '0', a good single frequency receiver will get you about 1m accuracy with good reception. 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). Simon _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
