I use Google maps. At full zoom a position can be located to within 10m in most parts of the civilized world and in most of the US for that matter.
Right now I am sitting at 52.143392N,0.117095E and my car is parked at 52.143390 0.117336E.
The difference in latitude is .000002 degrees and at 60 nautical miles per degree, or 111.12 km, that is 22cm. The difference in longitude is 0.000241 degrees but that must be divided by cos(latitude) to convert to an angular separation. The conversion factor is 0.613254320 according to my good old Chambers 7-figure log tables. Performing the division and multiplication yields a linear separation of 44m. In reality the car is about 1m north of me but the east-west distance is actually about 18m.
Good enough for me. Note that one arcsecond is 112120 / 3600 = 31m so my co-ordinates are good to an arcsecond or better.