[What means HVxxxx, etc]

Check out this page

http://www.ngs.noaa.gov/PC_PROD/DDPROC4.XX/dformat.htm#A.11

 

There is a reference to PID numbers under 3.3.1 field 3. While it is not clear, they would seem to be assigned simply in alphanumeric order, AA0001..ZZZZZZ.

 

You have 'AA' in Virginia which makes sense since expansion in this country was east to west. Here in Sacramento, CA, I deal with a lot of 'JS' prefixes.

 

Just a guess... I may be wrong.

[Wyoming DOT benchmarks]

Here is some general info I found on the DOT website... for whatever its worth.

 

http://www.wfl.fha.dot.gov/design/manual/pddmch05.pdf

[Can new Benchmarks be placed?]

Here is an example of a survey grade GPS. I'm sure it costs big $$$.

http://www.leica-geosystems.com/gps/product/sr530.htm

[This is all very interesting.... BUT...]

Go to http://www.geocaching.com/mark/

Try searching by your zip code to start with.

[How do *you* find them?!]

Here in Sacramento, CA I will use the GPS if the benchmark is of fairly recent vintage, and has "GPS observations". The older benchmarks typically do not, and are just a guesstimate from a map, in which case I'll use the description to locate it. You can tell if a "GPS OBS" was made by clicking the "view original datasheet" link at the top of the benchmark page, and looking for GPS related info on the page. Here is an example-- http://www.geocaching.com/mark/bench.asp?PID=AC9233

The coordinates supplied by the GPS observations are extrememly accurate, as they typically use dual frequency GPS survey sets to obtain them. Our handhelds only operate on one frequency. Hope that useful.

[How do *you* find them?!]

Here in Sacramento, CA I will use the GPS if the benchmark is of fairly recent vintage, and has "GPS observations". The older benchmarks typically do not, and are just a guesstimate from a map, in which case I'll use the description to locate it. You can tell if a "GPS OBS" was made by clicking the "view original datasheet" link at the top of the benchmark page, and looking for GPS related info on the page. Here is an example-- http://www.geocaching.com/mark/bench.asp?PID=AC9233

The coordinates supplied by the GPS observations are extrememly accurate, as they typically use dual frequency GPS survey sets to obtain them. Our handhelds only operate on one frequency. Hope that useful.