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I am probably backward thinking, but GPS (sat) and DGPS (land and naval) combination for precision applications is pretty good. I pinpointed a euro coin on a cl

I am probably backward thinking, but GPS (sat) and DGPS (land and naval) combination for precision applications is pretty good. I pinpointed a euro coin on a closed circuit of several hundred meters with an ordinary Trimble receiver which accepted DGPS corrections, and it was about 15 years ago. If Galileo eliminates need of DGPS around the EU, and is more cost-effective, its fantastic! UPD: also, I read back then that GPS signal is very accurate, submeter accuracy locations by default, but signal is artificially roughened, with clear data available for military use only.

UncleSlacky 10y ago
You're thinking of "Selective Availability", whereby a (random walk IIRC) was added to the signal to deliberately reduce accuracy. It was turned off in 2000 (though it could be turned back on at any time): https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...
- pacificmint 10y ago
  > though it could be turned back on at any time That's true right now, but the new GPS-III satellites do not have that feature anymore, so in the future it will not be possible to turn SA on again. The link you posted explicitly mentions that.
tinus_hn 10y ago
A large source of GPS inaccuracy is atmospheric variations that cause the signals to bend and delay. The data sent by the satellites contains information that can be used to correct for this but it is encrypted so only approved parties can use the resulting accuracy. Using a fixed nearby station as in DGPS is another way to correct for this.