|
Post by Malcore on Sept 5, 2007 19:30:46 GMT -9
While we were out at king mountain last weekend we tryed to find a few benchmarks in the area. Well we tryed to find TT1796 which should have been 330 ft. from our camp. But after looking all over we couldn't find it. After looking for another one a ways away and not finding it ether, we headed back to camp, about half way back we found a new benchmark along the way. After checking it out we found that it was what looks to be a RESET of F93. (TT1796) The question is, Is this a benchmark that would be logged on the original TT1796 page or would this be just another new benchmark that isn't logable? Here are some pictures: What do you all think?
|
|
|
Post by Malcore on Sept 5, 2007 20:01:42 GMT -9
OH, btw the new mark was found 580 ft. away from toe posted coords for the origonal.
|
|
|
Post by NorthWes on Sept 5, 2007 20:34:55 GMT -9
Unfortunately I think it's the latter case - a new benchmark that can't be logged on the 'old' gc.com database - even though it's stamped as a reset of F 93. It's clearly not the F 93 that was placed in 1964 and issued the TT1796 PID>
Funny you asked - a question similar to this was presented on the gc.com benchmark forum today, focused on reset triangulation stations. I'll paraphrase the gist of it here:
When a vertical control disk is reset, it is stamped with the original designation and the word RESET, and added to the database as a new PID. On triangulation stations, the "reset" mark is in the exact position as the original (reset above the subsurface mark), so there is no chance that there is an original AND the reset. It's a guess, but I'd suspect this is why the original PID is used--it preserves the history of the station.
Now, since the datasheet for TT1796 neither describes an underground mark (which we should never see, as they're set well below ground) nor calls the mark a 'triangulation station' we would infer that if the mark you found is a reset it would have a new PID (Permanent IDentifier, issued by the NGS). I did a search of the most current NGS database (updated for Alaska almost a year ago...) and found nothing within a five-mile radius of TT1796 that matches the description of what you've found and photographed.
I suspect you've found a mark placed by AK DOT using GPS controls which replaces the original TT1796 (F 93 1964), but which hasn't been submitted to the NGS for inclusion in the national database (probably for reasons of $). Since the NGS doesn't have a new PID listed which includes a description of the stamping on the mark you found (which would be the case for a 'pure' reset of a horizontal or vertical control station), I'm certain that although it's technically a reset for TT1796 it's not actually TT1796 - it's a state imposter! Tough to say it, but it's not TT1796 until the agency who placed it (re-monumented, or 'reset' the mark) submits a report to the NGS saying they've done so. Wierd that they didn't spend the extra e$$ort (er... effort) to make the report - the paperwork's cheaper than the money spent to reset the mark!
I'm just impressed you had the energy to benchmark hunt after that long hike!
|
|
|
Post by Malcore on Sept 5, 2007 21:15:32 GMT -9
That is a great explanation for the prossess and reason for it not being in the databace. From the location that we found it in I would say the people that placed it were doing it in conjection with the laying of burried telephone lines. Probibly the only reason they used the same id is it was the closest to the area. Thanks for the info and insite on how this works.
|
|