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Everything posted by Bill93

  1. A quick search found some relevant info, although I'm not sure it answers the "when" question. Old thread: https://forums.geocaching.com/GC/index.php?/topic/325390-benchmark-in-germany/ These have pictures with German labels. https://commons.wikimedia.org/wiki/Trig_points_and_benchmarks https://commons.wikimedia.org/wiki/Category:Wienblickwiese_Grenzstein
  2. I've seen yards many times in BM descriptions. See QK0329 for instance. It is almost never used for anything that was measured carefully, but not uncommon for "ballpark" distances to get you in the vicinity of a mark. The other place yards are used almost exclusively is golf.
  3. That's what I was complaining about. If they had converted to whole meters it would be fine, only a slight change in precision from +/-a couple yards to +/-a meter. But to decimeters??
  4. I reported a bunch of recoveries in the last couple months, and as I look at the results I see someone is editing them to provide dual units. I submitted one that gave an approximate tie from a field drive crossing the RR tracks. I put it in yards so no one would think I had taped it to the nearest foot. See what I got: 120 YDS (109.7 M) NORTHEAST OF A FIELD DRIVE Aarrgg! Take heed; do the conversions yourself in your recovery reports so the result doesn't look idiotic.
  5. Not for the Destroyed report, but I did submit NF saying "probably destroyed" before going back and spending more time with the metal detector to find the actual disks. So it is pretty easy to guess who actually reported it. I "removed the mark from the area to prevent confusion by someone putting it back near where it was." One of them was discussed and pictured here. I'm guessing that "Deb Brown" is now a job description and no longer the original person who handled it 15 years ago, and the present person performing that duty just did it differently.
  6. They are now marked destroyed. It's a bit different from ones I submitted years ago in that it says "Reported by Deb Brown" instead of having my name associated with the report.
  7. The data base has been updated with recovery reports I submitted via web form on Nov 22. That's quite up to date, about 5 working days ago! What's missing is action on a couple of destroyed marks that I sent in pictures of in July and August and, after seeing no action, duplicated in October. They have my NF reports, but in each case I went back and spent time with the metal detector and found the disk, one in part of the broken post and the other on its pipe laying horizontally under the grass. I'm pretty sure my photos are good enough to be sufficient for a Destroyed.
  8. That site has changed so the link above no longer works. There are new and informative posts to the thread. See https://rplstoday.com/community/gnss-geodesy/best-tool-for-calculating-distance-between-two-points-over-very-different-epochs/paged/1/
  9. You can always go look at the NGS data base for current information. Find the link for Benchmarks, choose your search method, and pick text, not shapefiles. https://www.ngs.noaa.gov I quickly tired of finding (or not) green match holders in conifer trees, and decided that while geocaching occasionally took me to interesting places I wouldn't have noticed, it wasn't otherwise a useful activity. Bench mark hunting (once I got a feel for what the professionals were interested in and how they described positions) lets me make a useful contribution by posting recoveries both here and to NGS, is still treasure hunting outdoors, sometimes involves historical research, and teaches me about geodetic science. I also like playing with some technical toys I acquired for that, including metal detector, magnetic locator, obsolescent theodolite, and now a rather old professional GPS receiver to submit files for GPS on Benchmarks that I've posted about.
  10. An interesting thread (and links) on the professional forum talks about Michelson's measurement of the speed of light in the 1920's and the assistance the US C&GS gave him. They ran a very long baseline to better accuracy than I can imagine, and triangulated to marks on two mountains. Michelson sent light from one to a mirror on the other and measured the round-trip travel time. https://rplstoday.com/community/threads/best-tool-for-calculating-distance-between-two-points-over-very-different-epochs.332509
  11. I agree, but ... You aren't always concerned with lat-lon. I've been doing OPUS Share submissions that I hope will be accepted for the GPS on Benchmarks program, and wondered if there would be some way to use those vertically mounted disks, for height only and not lat-lon. If you set up the GPS antenna say 50 ft away in the clear, and use an automatic level set at the height of the mark to set the ARP at the height of the mark, anyone who knows how to use the equipment should be able to match within a millimeter or so, well within the expected 2-4 cm accuracy of a 4-hour GPS session. I don't see any way to tie elevation only for the share submission to the PID in the NGS system. A procedure like this would improve the availability of stable points for GPS vs Leveling comparisons (the point of GPS on Benchmarks), because the other stable old marks are too often not suitable for use. They tend to be on railroad bridges too close to an active track (unless you have the budget for a RR flagman), or on culverts and bridges near a stream with a lot of trees, with more trees when the RR line is abandoned and thus easier to access. I looked at the data for 25 marks used to create Geoid12B in my area, and was shocked at how many concrete posts they used as opposed to more stable mountings. Only 3 were Stability B. The above paragraph may explain why-posts are more often out in the open. A side issue is that poured-in-place concrete posts are called C stability, and precast ones are D. I'd have to see evidence before I believed that was warranted. From what I've seen, the precast ones (if they don't get broken) at least guarantee a depth, whereas poured ones that I've seen out of the ground aren't necessarily as long, leaving me wondering about frost heave.
  12. Anybody can paint a triangle around a point for whatever meaning they want to give it for their own purposes. I don't see a 2-letter, 4-number PID there, which is the format used by NGS. I'd suggest that you not pursue the route of finding some mark and then trying to figure out what it is. Look in the geocaching data base for some marks that have been found by others and locate them yourself to get familiar with what is typically in that data base and the environments where the were typically set.
  13. It's almost certain these nails do not have high-accuracy geodetic coordinates, and won't be in the NGS data base so you can log them. They are either cadastral (property corners or reference marks to find those) or for construction (e.g. upcoming road work). A curb is not stable enough over decades, and a nail in a crack less so, but are useful in the shorter term. The painted numbers you see near those nails are the point identification the surveyor uses on this project, and won't be part of any larger scheme. It is rare to find the NGS PID (like AA1234) marked on an NGS point. Their procedures do not call for marking a PID, just a DESIGNATION. Sometimes a user will paint the PID on the concrete or a stake to help find it during their work in the area.
  14. Were they measured for inclusion in the data base? That's really what matters for logging here. Generaly, don't bother trying to put them in Waymarking if they weren't in the data base. A nail is usually a temporary mark unless set in a very solid mounting. You won't find many nails in the NGS data base and the geocaching list of benchmarks is an old snapshot of the NGS data. I HAVE seen a few nails in the data base, but they were part of US Geological Survey work that included disks and got added to NGS, but those nails (usually in wood) weren't really permanent enough and probably shouldn't have been included.
  15. I found this magnetic station in 2011 and got a short article in the county newspaper. I wanted a commemoration that surveyors might notice also, so I took several hours of GPS data and submitted an OPUS Shared Solution. These stations were used to measure magnetic declination and to let local surveyors calibrate their compasses by sights to landmarks. My submission: https://www.ngs.noaa.gov/OPUS/getDatasheet.jsp?PID=BBFS77&style=modern Find shared solutions: https://www.ngs.noaa.gov/OPUS/view.jsp
  16. No one can give you permission to keep the disk, so don't ask. Somewhere on the NGS site it says they should be sent back to NGS, but I've never heard of anyone doing that. There is a procedure for doing a RESET to a nearby position before the old one is destroyed, and reporting the new elevation, but I think it takes a digital level instrument that relatively few surveyors have to get data that NGS will accept. If this is in a local area with concerns about flooding, you might want to contact a local surveyor who does elevation certificates to alert them about the upcoming destruction. They might want to do their own unofficial reset if that was one they depended on. It is important to take photos proving the destruction, such as the disk in hand (if you aren't going to be there at the time or get hold of the disk try before and after photos of the site). Send those to deb.brown@noaa.gov so she can mark the data sheet as destroyed. It IS important to remove a destroyed disk from the area so no one creates confusion by putting it back near "where it used to be," although of course that won't happen to the one you are looking at.
  17. Good post. I would say though that the demise of passive bench marks will be gradual, and not all at once in 2022. Much existing work on older datums will stay on them and even be extended on them. There are city sewer systems and (I think) Corps of Engrs projects,even flood insurance maps on NGVD29, almost 3 decades after publication of NAVD88.
  18. The data base has been updated with recovery reports I submitted via web form on July 5. A couple from a week before that haven't appeared. I'll give them a little more time before assuming I screwed up the submission.
  19. If you have a smart phone, the app BenchMap is similar and color codes whether the last report is a found or not found.
  20. I have a lot of NF reports, but it's rare to find proof of destruction. This one appears to have been struck and cast aside when a fiber optic line was installed. I sent these pictures to NGS so they can mark it Destroyed. I'd never seen pictures of this pipe and spear point anchor design. It is an aluminum pipe with the aluminum cap and point having shafts driven into the pipe and a rivet to retain the cap. Overall length is about 30 inches. It has magnets on the top of the spear point, but they are too deep to produce a distinctive response in a magnetic locator.
  21. The NGS data base has been updated with recovery reports submitted June 12, and perhaps beyond.
  22. The way I read the current NGS data sheet, NGS probably has only one set of measurements for this mark. The superseded elevation is in NGVD29, the adjustment done shortly after 1929. The old measurement data for many bench marks plus that for some new marks were fitted in an adjustment with different assumptions/measurements for gravity around 1988 to get the NAVD88 datum elevations. This disk apparently didn't have enough data to suit them or some other problem so it was not actually fitted in the adjustment. Its updated elevation was computed using a generalized VERTCON model of lower accuracy to convert from NGVD29 to NAVD88. Also note the newer elevation estimate is higher than the old one, due to differences in the underlying model, so certainly those numbers do not reflect subsidence.
  23. For anyone interested in what goes on in making a coordinate reference frame deal with tectonic motion, NGS has a recent paper about the upcoming 2022 redefinition that will replace NAD83. It won't obsolete our handheld or car GPS receivers. But in order to work at cm level, there are many factors to consider. No fixed model can remain that accurate over time, due to not only the main tectonic motion, but distortions in the tectonic plate itself. The first part of the paper is very readable without a math background, although later it does get dense. I found the first few figures quite interesting.
  24. If you are looking for more search targets because you've pretty much exhausted your local area, you could try this list https://www.ngs.noaa.gov/OPUS/view.jsp This is a secondary list maintained by NGS, which accepts submissions of 4 hours+ of data from professional GPS units along with descriptive material and pictures. It takes much less effort than getting one into the main NSRS data base. This list includes submissions for the "GPS On Benchmarks" program which provides checks on GRAV-D. There aren't a lot of them in my area. I've mentioned in other threads (e.g this) how I have been using a nearly antique professional GPS receiver, and now I've submitted a few sessions to this data base. The one I consider most important fills a gap in their coverage of stations having both old leveling data and GPS observations. I also did a check on a point submitted by DOT, one on a reset disk that probably isn't so important, and got a new point entered for a USGS disk I happened across that's in a very nice accessible place so others might want to use it.
  25. I think Kayakbird has it: "it appears to me that the original 1934 has been slightly modified to 1954. My idea is that the post earthquake visit saw no reason to do a full reset" Compare the stamping of the 3 on N 46 KQ0340 The pictures have to be of the same disk. Someone didn't bother to figure out which mark they found when they went to log. Nobody has actually logged RM1 on geocaching.
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