On the topic of benchmarks, I found this official site earlier this morning.
http://www.ngs.noaa.gov/CORS-Proxy/NGSDataExplorer/ Joe Gray W5JG On Mon, May 2, 2016 at 1:49 PM, Wes <w...@triconet.org> wrote: > Nothing to do with time but... > > Technically speaking, in surveying a bench mark is a vertical control point. > In playing with Geocaching I've located bench marks that were placed in the > 1930's and never found again (until I did). There were often a hundred feet > or more from where the description had them. (Great fun BTW) > > See: https://www.geocaching.com/mark/ > > > On 5/2/2016 9:13 AM, Chris Albertson wrote: >> >> A man with a GPS knows where he is. A man with two GPS' not not sure. >> >> I've always wanted to walk my self-survey GPS over to a brass USGS >> benchmark and see it the GPS matches to benchmark location. OK, I've done >> this with a hand held GPS and gotten readings within about 10 meters. >> >> But before spending a lot of time removing the lat 10cm of error I'd do a >> test at the nearest BM that is not in the middle of a street. >> >> What has stopped me from doing this is that a few years ago I had to have >> my lot lines surveyed. They got to better then 1/10 of a foot at each >> corner and shot some brass markers into the concrete. Google can see >> my >> house's roof ridge lines and the concrete so I can work out the exact >> location of the roof mount antenna to within maybe 18 inches. It seems to >> agree with the survey as long as everyone uses WGS84. >> >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.