[time-nuts] USGS Benchmark accuracy...?
dave.powers at att.net
Wed Sep 14 14:42:46 UTC 2011
It has been a few years since I went to school on these, and there have been
some changes. Basically, to find out the specifics on the benchmarks, you can go
to the USGS website, and search for the benchmark, from the info on the brass
plate. You can find the 'Order' of the benchmark, which will tell you its
accuracy. In my time, there were 1st, 2nd, and 3rd order benchmarks, but they
have since re-surveyed some of the benchmarks, now designated as 'High
Accuracy'. Good luck. -
From: Michael Baker <mpb45 at clanbaker.org>
To: time-nuts at febo.com
Sent: Wed, September 14, 2011 7:39:44 AM
Subject: [time-nuts] USGS Benchmark accuracy...?
There is a USGS survey benchmark on the side of the road
just a half-mile from my house.
Any guess as to how accurate these are?
I parked my pickup truck over the benchmark with the LH
box and antenna ( a 10 year-old Trimble surveyors antenna).
I only let LH run for an hour-- I am not sure how I could
leave a LH box out there for a long survey period without
running the risk of theft. The survey marker is about 20 feet
off the side of the road in a grassy area and marked only by a
4-foot-tall plastic USGS geodetic pole next to the buried
The head of the marker post with the brass plate on the top
is flush with the surface, but covered with grass. I had to
scratch around to find it. There is also a second concrete post
in the ground about 30-40 feet away-- apparently you line up
the two concrete markers to give you a true cardinal direction.
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