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Ngs's Data Basement

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I was intrigued by noticing files of nonpublished PIDs.


To access them, start with the NGS datasheet page.

Click on Archived Datasheets, Yearly_Archives, select as state, click on Get Misc Files, click on the last option, the unpublished stations, and download the file.


I recommend importing the resulting file into a spreadsheet and sorting it by H and v columns. Ignore all rows except the ones with code D (No Descriptive Text Available). Also, ignore all the marks except those whose horizontal coordinates have 0.1 second precision.


In the group that's left are a weird collection of PIDs, with coordinates, some of which are Azimuth marks. In many cases, the datasheet of the azimuth mark's primary station doesn't include the PID of the azimuth mark and never the coordinates of the azimuth mark. Usually the main station's datasheet includes the azimuth mark's to-reach description, but not always, and the description may be so out of date as to be unusable. So, here's another resource to find some of those trickier azimuth marks with a GPS receiver. An example is HV8814 with its azimuth mark HV8815. (Yes, the datasheet for HV8815 has the coordinates, but HV8814 doesn't give its PID.)


Then, there's the rest of the marks in the list of D-code and 0.1 second coordinate precision. A real challenge here! Not coded destroyed, so possibly findable. So I wrote to Deb Brown at NGS, asking her about these D-code marks, and whether she'd like us to submit any recoveries on them. She replied that, for these marks, they simply didn't get a complete description for them. She also said that yes, if we could provide complete descriptions for any of them, to send them to her VIA EMAIL (not via the mark recovery page), and they'd add them by hand in the office. Of course, since there is no description of the mark to work with, finding a disk with the proper designation on it would be required. Of course, there's no assurance that any given PID in these lists even has a disk. Good luck!

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The NGS Datasheet Retrieval mechanism works in mysterious ways. Lets use the aforementioned HV8815 WEST HAYMARKET AZ MK as an example. If you try to download the Datasheet directly using the following link:


you get this result:

 Pid    Name                           Lat        Lon         Elev     O o Hv
 ------ ------------------------------ ---------- ----------- -------- - - --
>HV8815 WEST HAYMARKET AZ MK           38 48 49.4/077 37 52.9          3   D 


So, it looks publishable if you can get some Descriptive Text.


But now try this. Go to the NGS DATASHEET RETRIEVAL PAGE .

Click on Station Name. (This works for the other retrieval methods too.)

By Station Name type in "WEST HAYMARKET", Choose Virginia as the state, and check the little box at the bottom that says Browse Mode before you submit. It will return this page to you:

|Dist|PID...|H V|Vert_Source|Approx.|Approx..|Stab|Designation

|----|------|- -|-----------|-------|--------|----|-----------

|....|HV8814|2 .|29/GPS OBS.|N384901|W0773818|C...|WEST HAYMARKET

|....|HV8815|3 .|29/VERT ANG|N384849|W0773753|....|WEST HAYMARKET AZ MK


Click on WEST HAYMARKET AZ MK and then click GET DATASHEETS. It will return this:

 Pid    Name                           Lat        Lon         Elev     O o Hv
 ------ ------------------------------ ---------- ----------- -------- - - --
>HV8815 WEST HAYMARKET AZ MK           38 48 49.4/077 37 52.9          3   D 
>HV8815 WEST HAYMARKET AZ MK           38 48 49.4/077 37 52.9          3   NN


The letter "N" means "No geodetic control at this mark ". This is true for both Horizontal and Vertical.


What is the precise meaning of "No geodetic control at this mark "? Doesn't this mean that no precise measurements by NGS standards are on record? Therefore, even with Descriptive Text, it is still unpublishable. Or does it mean something else?

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To answer my own question (in part), I think it must be true that there was Geodetic Control done on HAYMARKET AZ MK, because it is listed in the above chart as Horizontal Order 3. So my question is, why is it listed as "No geodetic control at this mark "? Is the Geodetic Control still in a paper file somewhere, just never entered into the computer database?

Edited by TerraVador
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