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NGS datasheet iinfo


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I've notice on several datasheets for benchmarks that they have "HD_HELD1" coordinates instead of the usual scaled coordinates.


Here is an example of a datasheet showing it: http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=PH0307 More marks along that line are the same way. Please note that the only history on the sheet is from 1942.


Anybody have any ideas on where NGS might have come up with the data on the sheet?



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HD_HELD1 = Differentially corrected hand held GPS observations. (Lat,Lon Rounded to 2 decimal places.)

HD_HELD2 = Autonomous hand held GPS observations. (Lat,Lon Rounded to 1 decimal places.)


Apparently someone's been to the mark, just didn't bother to log it as a recovery

Edited by gpsblake
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Here are five PIDs to make you scratch your head..... PH0195, PH0201, PH0211, PH0214, PH0227.


They are all for benchmarks and are showing a HD_HELD1 coordinates. AND all five datasheets are indicating that they are "MARK NOT FOUND" in the 1970s. And of course they don't have a "FOUND" status on Geocaching website.



Edited by kayakingphotos
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A bench mark does not have to be found to have either an HH 1 or HH 2 position. First note that the NGS description of an HH 1 position is "The horizontal coordinates were determined by differentially corrected

hand held GPS observations or other comparable positioning techniques and have an estimated accuracy of +/- 3 meters." Many marks were positioned by "other" positioning techniques. During my final three years at NGS I made an effort to harvest horizontal positions determined by the U.S. Geological Survey (USGS) for many bench marks for which NGS had only a scaled position. These data had never been submitted by USGS to USC&GS/NGS for inclusion into the national network but were none the less of at least third-order accuracy which more than meters the requirement for an HH 1 position. Unfortunately I was probably the last one at NGS who even knew these data existed and could still be of some use. Another set of marks that often had scaled positions were Reference Marks for triangulation stations that were also bench marks. It was a rather simple process to compute the position of RMs from the azimuth and distances provided on the NGS datasheets. These values also more than meet the requirement for HH 1.

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