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Bill93

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Everything posted by Bill93

  1. Don't confuse USGS (US Geological Survey) who made the maps versus the NGS (National Geodetic Survey, formerly called US Coast and Geodetic Survey). NGS maintains the master control network of lat/lon and elevation references. USGS worked off of those and set many additional disks or other marks as needed for mapping and water monitoring. If NGS happened to find a USGS point convenient they may have measured it to their standards and added it to their data base, but that is a minority of USGS marks. USGS never computerized their data sheets, and most are only available from filing cabinets.
  2. I did this once some years ago. See the first log for MH0134. The ties hadn't checked out, which I later blamed on changes to the RR, grading of the adjacent lot, and widening of the street. The mark was beside a RR signal building and I thought it likely construction would have disturbed it. On a hot Sunday I did a 1-way run with my wife holding the rod. I wasn't up to closing the loop in the heat. Calculations showed it checked better than I had reason to hope, so reported GOOD. Sadly, in 2018 i went back to it to do a GPSonBM session and found fresh tracks where equipment had hit the post, breaking it and possibly driving the base deeper. DESTROYED. That session would have filled a big gap in the GPSonBM coverage, and every other mark in the neighborhood has poor sky and/or would risk trouble with the RR.
  3. The only time a mark is worse than disturbed is when somebody puts it back "about where it was" so it doesn't look disturbed when a surveyor tries to use it.
  4. The ones I referred to are disk on rod set in a clay tile. There is no sleeve on the rod. The tile is partially filled with gravel to attempt to drain water away, but I doubt that is fully effective.
  5. The Power Squadron had a lot of volunteers with little training, and their reports are not to be taken as authoritative. If they found something that looked like it could be the bench mark they usually reported GOOD. A report of NOT FOUND could sometimes mean little effort was put in to looking for it. And rarely do their reports add or update the to-reach description. So their reports are helpful but not great.
  6. I'd say POOR with the description of what you saw. A side view photo would be a good addition. Has the location settled with the rod remaining at its original height? Is the cover surrounded by dirt or set in concrete? I have seen a lot of USGS rods (short ones, I think) sticking above the surroundings in Iowa. A rod with no protective sleeve can get lifted by freeze-thaw cycles. But your area doesn't get deep frost, does it? Is the rod bent or the ball scored by a pry bar? Did someone put something other than the original steel ball on the rod? Just trying to consider all possibilities.
  7. NGS has occasionally updated the wish list, but I wouldn't have a lot of confidence they would in response to a few missing in an area. Very few on their list are going to get sessions submitted by volunteers with the equipment. NGS has to work with whatever they get that is useful. If someone does submit sessions on suitable replacements I think they will use them even though those weren't on this list. The replacements may not be as optimally located, which is why they weren't chosen for the list. In the earlier round . I looked on Google Earth for every disk location along a former RR line for 50 miles for ones without tree cover, went out and found only three existing stable and with suitable sky to submit, and those weren't all on the list but they used them.
  8. There are many marks on their list that just need a recovery report so someone with the equipment might have more incentive to submit sessions on them. The GPS requirement is L1+L2 (non-squaring process), which is beyond recreational and mapping receivers. It takes a professional grade receiver with an antenna model having NGS calibration data, centered and height measured to mm precision, with minimum of 4-hour session. The data is processed through OPUS. In 2018 I submitted 27 sessions using an antique but sufficiently capable Trimble 4000sse receiver. There was a lot to learn and lots of hours put in, but an interesting project. Maybe again next spring.
  9. Each country may have a few across the border, but it seems their data bases don't overlap. Even though the BM at Father Point is the reference for all of our NAVD88 elevations and has an NGS PID, you can't get an NGS data sheet for it.
  10. If you are in Cary, do you know Paul, a real estate guy who used to be very active in this forum as PFF?
  11. Looks like a reference tie (see words on tag) to a nearby bench mark that is harder to find, or possibly a temporary bench mark itself if the tag was all the crew had to label it with so the words don't really mean it. I see nothing cadastral about it, as it isn't labeled as a property corner might be. If it were for horizontal position measurements on a project, folks around here probably would have called it Control Point CP1. Did you see any evidence of nearby construction? Is this a location where a flood plain elevation certificate might be needed for a nearby building?
  12. Well, I guess it's better to have no data than to have the wrong data. My favorite wrong marks have always been the three which were carefully reset from marks number 5, 8, and 12 (possibly county or USGS numbers?) and new NGS data sheets made. The trouble was that those 5, 8, and 12 weren't in the NGS data base, and the resets were calculated from 5, 8, and 12 in another county so they were most of 100 feet off in elevation and scaled coordinates maybe 60 miles off from where the To-Reach took you. At least one (Geocaching) (NGS aa3904) would be a really nice location for a GPS mark.
  13. I don't see it as a big deal, but a small step in a good direction. The only places it matters in practice are State Plane Coordinates, and also very long projects like highways and pipelines if they don't use SPC. SPC typically involves millions of feet from the grid origin, so the wrong foot is a serious discrepancy there. For somebody doing a survey in a square mile laid out with a chain in the 1800's and perhaps remeasured with a steel tape in the mid-20th century, it doesn't matter. NGS and the states will define new plane coordinate systems for the 2022 datum in meters, and anybody who wants feet will consistently convert to International feet. If referring to older work, people will still need to know which foot was used for the coordinates.
  14. The original disk in the wall must have gotten removed and somebody decided to replace it in 1992. Since then it was not based off of the original I5, it couldn't be a reset, but would have to be measured from other bench marks. Indiana does have a 370 line, so although that did not fill out the alphabet I can see why they went to 371. I'll bet more 371 disks could be stumbled across in that vicinity. But the 371 series measurements seems to have not been completed or the measurements rejected for procedures and quality so no data sheets.
  15. Minnesota crew submitted quite a few GPS sessions on marks in northern Iowa as part of their very extensive height modernization. I found one mark that had two PIDs, one with data from each state"s agency: ON0828 AE2132 And they didn't agree by almost exactly 1 meter in one of the XYZ coordinates. After I pestered NGS and the agencies for a while it got corrected. The incorrect redundant data sheet was deleted. I learned from that exercise that PIDs are not really permanent, because the PID of the deleted data sheet got reassigned to a new point a long way from there. That left an incorrect cross reference in my recovery report for the good one.
  16. Someone undoubtedly got the abbreviation for Montana wrong, as it isn't far from that state, and it is common to check a little way into adjacent states.
  17. While I agree most of the advice is good, this seems a bit too restrictive. If you can update the To Reach information in a meaningful way, then certainly do so. If the coordinates on the data sheet are SCALED, a sport GPS or a GPS app on a smart phone (HH2 accuracy) can be a worthwhile improvement. Never try to change ADJUSTED or GPS coordinates.
  18. It depends on the area. I have often dug for bench marks in rural road right-of-way after probe and/or metal detector hit, sometimes just sweeping off a thin layer of vegetation, usually only a few inches down, but occasionally more. I have also been chased away a couple times while looking (not digging) in such areas by suspicious owners of adjacent land. If it looks like a lawn or there are structures nearby, then you need permission. Digging too close to active railroad tracks is very definitely a way to get in big trouble. I once got permission to dig for triangulation station LE0530 out in a field and found the underground mark 27 inches down (surface mark long gone) after careful measurement from reference marks.
  19. Geocaching has the options Found, Not Found , Note, and Destroyed. The focus there is on your activity, with the option to also alert others to the likelyhood it is destroyed or to note something of interest. NGS has options that focus on the bench mark, not your experience looking for it. Thus the options are Good, Poor, and Not Found. Also Destroyed is an option available by sending conclusive evidence to NGS; they don't want to risk people marking Destroyed just because they couldn't find it. There is really no need for a Note option for their purposes. It appears NGS has greatly expanded the list of agency codes. GEOCAC appears under Miscellaneous.
  20. It's a land survey corner. Those are only very rarely measured as benchmarks, so I'm not surprised you didn't find it in the list.
  21. A measuring tape is more important than a metal detector, but after you have measured to a likely spot and don't see a disk, a metal detector is useful. The sequence should be: 1. Pick a mark using the Geocaching site and read any logs for clues. 2. Look at the NGS site data sheet for the latest logs. 3. Use the GPS to figure out where to park the car. 4. If it is a triangulation station (ADJUSTED horizontal coordinates) or has been measured by GPS, use your GPS to get closer. Look over the situation and figure out if anyone will object to your search. 5. If you don't see it, use the to-reach description and tape from any objects it lists that are still there. 6. If you find a disk in the vicinity of a triangulation station, look carefully at the marking to see if it is the station or a reference mark. The tri station is often buried and its reference marks not. 7. If you think you know about where a disk should be and don't see it, try probing with a long screwdriver or other tool. Often an elevation bench mark will be covered by decades of accumulated vegetation turning into soil. 8. If all else fails, get out the metal detector and search. 9. Before digging, look around the area for signs of buried utilities. The last thing you want to happen is a cut line. 10. If you have to dig, a hand trowel is safer than a shovel and usually fast enough for the depth your metal detector works. 11. If you find something, make very sure it is the one described on the data sheet. There are too many FOUND logs where they saw a reference mark, a RESET instead of an original or a different agency's disk. The metal detector is only occasionally needed, and then any working machine is usually adequate. You don't need a top of the line coin hunter to find a 3-inch bronze disk at 6 inches. Practice with whatever detector you have before going out to look for bench marks so you know its capabilities. Have fun and good luck.
  22. Azimuth marks were sighted from triangulation stations. Line of sight would use the great circle. Fortunately, that is going to be easier to compute than rhumb. There probably are few if any such marks far enough north that it will make a serious difference, especially over the distance of an az mark. For moderate distances spherical calculations will be close enough. For miles to hundreds of miles, depending on desired accuracy, you need to work on the ellipsoid model of the earth. For precise calculations you need to consider height above the ellipsoid, changing your local earth radius and thus the length of a degree. NGS has a toolkit on their site that helps with calculations. You should look at FORWARD and INVERSE. Long boundary lines run on the ground (e.g., public land surveys dividing up a state into mile-square sections) were run as a series of sights of whatever length worked, up to a mile, nearly always N, E ,S, or W. Over a longer distance they were thus close to thumb lines. Some state boundaries were specified to be a parallel of latitude, and thus a thumb line.
  23. There are many USGS disks that were not included in the US Coast and Geodetic Survey (now National Geodetic Survey) data base that is on line. USGS data was never computerized. They were not included because either the data was not submitted to US CGS, or only collected to mapping accuracy and not to geodetic accuracy standards and methods.
  24. But if you put one too close to a bench mark some geocacher will still claim a find for it.
  25. Sorry, I haven't researched this. I was just struck by the irony of what looks like a survey market that says it isn't.
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