Originally Posted By: Am_Fear_Liath_Mor
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Maximum Accuracy would typically be;

GPS - 8-10 metres with Selective Availability turned off

GPS + (WASS or EGNOS) - 5-8 metres

GPS + (WAAS or EGNOS) + GLONASS i.e. the Garmin Glo - 2-3 metres

DGPS - 1-2 metres depending on baseline distance

RTK GPS (phase measurement with small baseline distances) - 0.01-0.02 metres

In the UK the mapping accuracy for OSGB36 grid mapping is typically 2-3 metres for a OSGB map triangulation point so DPGS and RTK GPS would be rather pointless for general navigation.


Even 8-10 meters of accuracy is probably more than sufficient for most outdoor purposes. (Exceptions might be geocaching and a few other applications.) Back in the dark ages before GPS, we sometimes thought we were doing pretty well to locate ourselves within a 100 meters (depending on terrain). Ah.... but I am showing my age smile

Of course I'm a bit biased from living in Alaska. For many areas outside town, the best available topo maps date from the '50s and '60s, and are at 1:63,360. In really remote areas some of these were done with very sketchy primary geodetic control, and there are some serious accuracy busts in some places (this shows up when one tries to splice two paper maps together). Areas closer to major towns have been revised more recently, and in a few places we are lucky enough have recent 1:25,000 maps, but those are exceptions.
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