[time-nuts] Averaging Location for Position Hold

Chris Albertson albertson.chris at gmail.com
Wed Sep 14 14:50:03 UTC 2011

On Tue, Sep 13, 2011 at 11:22 PM, Don Latham <djl at montana.com> wrote:
> Just looked up all USGS maintained benchmarks within 30 mi radius of my
> home. One, at about 1.7 mi is a class A. the search site is
> http://www.ngs.noaa.gov/cgi-bin/ds_radius.prl
> Took me less than 5 min to find it via Google.
> Don

The USGS also makes good topo maps and now they have all those maps
scanned at full resolution and on-line.  (Googlle will find them.)
THe makes are very large scale and show all the benchmarks, section
markers and so on.   All of them were ground checked too.  The maps
tells you if the benchmark is in a reasonable place before you go and
look.  For example the one nearest me is on the center of a four lane
road with much traffic.

I hear that there is a hobby where people photograph these and collect
the photos.  Seems pointless in the city but many are on mountain
peaks and other places with good views.  The hobby is more reasonable
if you find them without using GPS.  The USGS maps are good enough o
put you within 10 to 20 feet of the BM without using a GPS.

Chris Albertson
Redondo Beach, California

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