[GeoStL] Re: Unlisted Benchmarks?
- From: Roger Barnes <rogbarn@xxxxxx>
- To: geocaching@xxxxxxxxxxxxx
- Date: Mon, 21 Mar 2005 18:29:58 -0600
-
The generic term is benchmark even though they are used for many
different purposes. It sounds like what you found were land survey
markers (section corners or similar) and/or land boundary markers.
Section corners (or half corner or quarter corners) mark the corners of
the land survey system of ranges and townships. They are generally
placed by the GLO (General Land Office) and its predecessors. Boundary
markers could be set by any licensed surveyor. It is rare to find
either on GC. That is because GC took it's database from the NGS
(National Geodetic Survey). To be included in the NGS database, a lot
of survey work plus paper work must be submitted to meet their
standards. There are several types of markers in the NGS database, true
benchmarks that measure elevation, triangulation stations that measure
precise latitude and longitude for geodetic purposes and other similar
markers. They are placed by the NGS, it's predecessor CGS (Coast &
Geodetic Survey) and many public and private agencies. Another source
of markers is the USGS (US Geological Survey). A few but not many of
their markers are in the NGS database, usually because someone else
(possibly the NGS itself) used a USGS marker for themselves and the data
was submitted to the NGS database.
This is a quick and short discussion of benchmarks. If you have more
questions, please ask!
Roger
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