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m&h

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Everything posted by m&h

  1. Kurt-- Thanks for showing us that view! When we found this station in January of 2006, we were a little puzzled to see that it had been found many times by geocachers, but that the latest report on the data sheet was in 1905. We still haven't really figured out why that was. Enjoy your trip! Cheers,
  2. Traverse and triangulation are not the same thing, but the USC&GS carried out both kinds of survey and on several (or many?) occasions used traverse disks at points which the data sheets call triangulation stations. We don't know why a traverse disk would be used at a tri-station, but yours is an instance. If you read the prose description at the end of the data sheet as found on the NGS site, you find it plainly stated that the station is a traverse disk, but up in the marker type area it's labeled DS = Triangulation Station Disk. VERY briefly and oversimply, a triangulation is a network of connected triangles laid out trigonometrically between baselines measured to almost unbelievable tolerances of accuracy. A traverse is a sequence of lines not interconnected, established by measuring angles at end points and linear-measuring to the next end point. A traverse could be open, going zigging and zagging along from here to there, or it could be closed into a large polygon so that additional checks could be brought to bear on the angles and distances. The CGS had standards of accuracy for both kinds of survey, and determined that traverse was sometimes preferable in areas where it was very hard to locate points that were far enough apart to be useful, yet still intervisible. Flat and timbered country, for example. Not like southern Arizona, where we would imagine the station was in fact triangulated, as the data sheet indicates that it was. We hope we're in deep enough to encourage expert comment, and not so deep as to scare it away.
  3. Thanks for the kind words. Yes, it was the blank whiteness of Curry County that drew us to look for something along our southward route in January.
  4. Holograph-- Many thanks, as always, for the amazing work you do for all of us. As for the westernmostness, well, we hadn't realized that possibility. So thanks for that too. Cheers,
  5. This thread should probably be in the Benchmarking forum. Anyway, is there any identifying material on the witness post?
  6. Some further thoughts. BDT--our own practice is to send an e-mail to Deb Brown when we are confident of a mark's destruction, and not to log it at all, but just to wait a while and see how NGS responds. But we believe we have seen on other threads the argument we describe for not reporting destruction. Bill93--The above would probably be our approach to (1) and (2), even though we found the mark, as you say. You are quite right that only the pros can decide for sure whether a mark has any use left in it, but we feel that it was ignorance that led us to doubt the destruction of PE0286. We photographed it in a piece of its original setting which had been moved from a seawall to the top of a hill. As to E 55, maybe somebody is experimenting with a new stability classification.
  7. The mark's geodetic position is the issue. If it is not where it was set, then by NGS standards--or any other surveying standards we know of--it is destroyed, because it is useless as a point from which to take any measurements, linear or angular. It is not immediately obvious to all that a mark you can see, whose stamping is legible, is destroyed, but if it isn't where it belongs, it is destroyed. For a good example of our own early failure to grasp this, see PE0286. So (1) and (2) meet the criteria for destroyed. In our opinion, (3) also does, because the post is broken off far enough below the level of the disk that the best you can do for a position is pray that the disk was set above the center of the remaining piece of the post. For most purposes this will not be sufficient, to put it mildly. There is disagreement about how to log these. One school of thought holds that for an NGS report, checking the not found box and saying in the comment box that destruction appears likely is a procedure preferable to sending Deb Brown compelling evidence of destruction. One reason is that potentially useful information about the disk remains as readily accessible as that in any other active data sheet. True, data about destroyed marks can be extracted from the NGS site, but that requires a few more keystrokes and the awareness that it can be done. For a Geocaching log, we can think of no argument against logging a mark as destroyed except doubt in one's own competence to make the call. Cheers,
  8. Geo-- We were exclaiming over this feature ourselves a few days ago. Of course in each locality there may be some variation in the available dates of imagery. Just a couple of days ago we were able to use it to find out where the center-line of a road was when it was still only one two-way lane, and which side of the original road the new lane was built on. And as you say, it's just a lot of fun even when you have no specific question to ask it. Cheers,
  9. Apologies for above post, which was made in haste. We see that you want disks OUTSIDE the dates in the list. Sorry.
  10. Monumented 1935 Photographed 5/19/2005 Massachusetts AJ4075
  11. One reason that often accounts for the difference between adjusted and scaled coordinates is that horizontal control stations are located with maximum attention to horizontal accuracy, and vertical control, or leveling, stations are located with maximum attention to vertical accuracy. These latter are the stations that are most correctly referred to as "bench marks." They are set during leveling runs, and their horizontal location often need be no more precise than what will serve to get you there. Cheers,
  12. A clarification that has often been made in these forums might be useful again here. The U. S. Geological Survey and the National Geodetic Survey are separate agencies. Quite a few Geological Survey disks meet the NGS accuracy standards and may be found in the NGS database, but the vast majority do not and may not. Cheers,
  13. The marks in this database are limited to those that meet the National Geodetic Survey's accuracy standards for either horizontal position or elevation. Furthermore, there are quite a number that meet those standards, and are in the NGS's files, but not in the Geocaching database, which is eight or ten years old. Untold thousands of other marks are out there, having been set by states, counties, cities, or by individual surveying firms marking property boundaries--among other possibilities. Is the stamping you quoted all there is on the mark? Is there no agency information around the outer edge? Can you get reliable consumer-grade handheld coordinates? A photo? These additional pieces of information could help you, and readers of the thread, figure out where to head with inquiries. Cheers,
  14. A postscript, after several minutes of fiddling around. The oldest available shot of this location on GE Pro is dated February 12, 1996, and appears to show the same tank as the most recent shot, though from a slightly different angle. Not fiercely sharp, but four legs still looks right. Another by the way: the historical imagery feature may be available in the latest free version of Google Earth. We haven't checked that. Cheers,
  15. Google Earth Pro usually includes an "imagery date" as well as the more recent copyright year. Its shot of this tank, which indeed has four legs, carries an imagery date of March 8, 2006. This imagery date feature, incidentally, enables GE Pro to do chronological slide shows of all the different shots of a given area. Cheers,
  16. Would this be another hint? Tighten up those stretch marks! Get out and hunt for bench marks! The sedentary, passive life leads from light to massive. Very great finds, by the way. Wonderful to read about. Cheers,
  17. Bill93-- Thanks for the tips. We'll use them.
  18. We apologize for the multiple posts above. We were getting "server not responding" messages that led us to keep trying.
  19. The database of NGS marks maintained here was obtained in about the year 2000, and has not been updated since. For more on this topic, see the FAQ in the Benchmark Hunting page. Strictly speaking, the term "bench mark" (usually two words) denotes a vertical control mark, an elevation. On this site the one-word term is used to denote both vertical and horizontal stations. Both kinds are included in the database. Cheers,
  20. The database of NGS marks maintained here was obtained in about the year 2000, and has not been updated since. For more on this topic, see the FAQ in the Benchmark Hunting page. Strictly speaking, the term "bench mark" (usually two words) denotes a vertical control mark, an elevation. On this site the one-word term is used to denote both vertical and horizontal stations. Both kinds are included in the database. Cheers,
  21. The database of NGS marks maintained here was obtained in about the year 2000, and has not been updated since. For more on this topic, see the FAQ in the Benchmark Hunting page. Strictly speaking, the term "bench mark" (usually two words) denotes a vertical control mark, an elevation. On this site the one-word term is used to denote both vertical and horizontal stations. Cheers,
  22. Paul-- A P.S. after doing a little more nosing around. You've found six or seven times as many marks as we have, so these observations are offered with diffidence and respect. If the decimalized coordinates in your forum post are changed to 34.217889, -77.81225 then the data sheet that matches is EA0624. The vicinity photo in your Geocac log for that mark appears to match the photo you have posted on Google Earth somewhat to the southeast.
  23. Thanks for the clarification, Paul. Next question: Why does a radial search on those coordinates not pull in an NGS data sheet closer than 0.2 miles? (We converted your decimals to DD mm ss.ss, and checked them on GE to make sure they still landed on your spot.)
  24. "If you use GoogleEarth, copy and paste this in the "fly to" box, and look in the foreground: 34.216170, -77.793345" Where is the foreground in an aerial shot?
  25. The only Eccentric mark we ever found was a disk. It is UT0565, SANKATY LH ECC 1979Details for Benchmark: UT0565, on a catwalk of the Sankaty Head Lighthouse on the east end of Nantucket. The Lighthouse itself was an intersection station (UT0553)Details for Benchmark:UT0553, but obviously no instrument could occupy it. Several months ago,incidentally, we read news reports of the lighthouse's removal to a safer place, west of the eroding shoreline. So both marks were thereby destroyed, however intact they may appear. We haven't reported that to NGS, though we sent in a couple of the urls for the news reports, because we haven't revisited the site.
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