m&h
-
Posts
282 -
Joined
-
Last visited
Posts posted by m&h
-
-
We see your
, so we figure you actually know that there's a good reason, not a mere excuse. Off-center punch marks are probably more plentiful than on-center punch marks. The point is surveyed, the pipe driven and capped, and then the precise point is measured again and found to be not in the exact center of the disk. They punch it where it is. -
The Principal Meridians and Base Lines of the Public Land Surveys, as far as we know, rarely or never coincided with the shorter meridian lines discussed above. Their purposes are different. The short meridian lines were laid out so that surveyors in the locality could calibrate their compasses. The PLS meridians and base line parallels of latitude established intersections from which the townships, sections, and smaller divisions of sections could be numbered and located. The PLS required regular astronomical checks of the meridian lines, rather than much use of the compass. Nevertheless, this map is a great help to anyone concerned with the history of the Public Land Surveys.
-
More on the Nantucket meridian markers.
The older set is a pair, surveyed and placed in 1840. They are not in the NGS database. They are handsome but worn marble obelisks about three and a half feet tall; one is on the north side of Main Street opposite the intersection with Fair Street, and the other is about 340 feet south up Fair Street on its west side. A few years ago, local astronomers checked it out with a K&E transit and found it to be 3.5 plus or minus .8 minutes off, which they considered too big an error for a skilled operator in 1840. They guess that construction disturbances caused the error.
The more recent set was placed in 1887, and consists of three octagonal stone posts originally about two feet high. They are in the NGS database; south to north, they are LW4252, LW4251, and LW4184. Fiddling with their coordinates with one program or another will demonstrate that they are not dead on true north either; the data sheets put the error at 28 minutes. It should be noted here as elsewhere that the south stone was broken off below ground level many years ago, but its base is still in place about nine inches from the surface of the ground. The south and north stones are 132.7776 meters apart, and the middle stone is a little over a meter north of the mid-point.
-
We looked at the photo announcing Robespierre's find of this cache. A fabulous object! We suppose your guess about who has the key is as good as ours, but if we were in that area we would be all over the phone trying to find out. It's tempting to think that occasional checks of the azimuth have been made and then recorded for placement in the box. (This is assuming that the other mark is still extant somewhere within a few hundred feet.)
There are two sets of meridian markers on Nantucket Island, one in town and one out on the south side of the island. We'll be back in a little while with more info about them; getting it together right now might take long enough to time us out.
-
As always, a superb combination of usefulness and elegance. Many thanks.
-
Holograph--
Another fabulous piece of work. Many thanks.
-
P.S. Take a look at mloser's great photos in the thread "what does the disk look like beneath its setting?"
-
When you say "take," do you mean "log," or "pick up and abscond with"? If the latter, the short answer is that you can't. Now for something a little longer:
If a mark's whole setting, such as a bridge abutment, has been removed, the destruction is obvious and the mark has vanished. But say instead that the abutment has begun to crumble around the setting of a disk, and the disk itself has worked loose, maybe heaved all the way out of its setting. So it exists, and in that sense is not "destroyed," but its value as a precise mark of an exact point on the earth's surface is now zero. That is the kind of destroyed mark that appears to be available for the taking. HOWEVER, it remains the property of the NGS, and they don't want you to just walk off with it, even if it's lying on its side several feet from where it was set. If you notify Deb Brown of its condition, and document it with photos, she may well offer to let you have the disk. That is not taking it, but rather accepting it as a gift.
-
There is a fairly extensive website maintained by the Lower Colorado River Authority <www.lcra.org>. A cursory flip through it turned up no information on survey markers, but they have a Contact Us page.
Good hunting!
-
The persuasive group above includes some people whose expertise we’ve respected and benefited from since we joined the forum. The legs of the square are obviously indented, no matter how the photos look to us, and that’s the salient point. Our caution, which may sometimes have kept us from reporting good finds, does want to remind us that the data sheet is unusually reticent: it’s easy to locate the correct bridge, and its north end, but it would have been nice to have a little more: East rail? West rail? Measurements from the roadway center line and one or two durable points along the railing would be good to have in the recovery report.
-
This strikes us as a pretty long shot. It is not always easy in digital photos to distinguish raised and depressed parts of a close-up object, but the three remaining sides of the square you found have a raised or molded look, rather different from the usual chiseled square, which is carved down into the surface, and is rougher around the edges. What you have here could conceivably be some molded portion of the concrete block. The description on the NGS data sheet is vague as to what part of the bridge the mark is on; “north end” narrows it down some, but there are still plenty of questions. Furthermore the coordinates are scaled. It is possible that you and your predecessor have made a nice find, but if the pictures are showing what’s there, we would probably not have reported this even to this site, let alone the NGS. We may be over-cautious sometimes.
-
And you still found time to advise and encourage newcomers like us. Bravo!
-
A note or two from our experience, which is less extensive than that of many others here--
To report a mark destroyed to this site, be sure you are correct, and include some persuasive photos. If the mark was a disk, get as close as you can to where it was and take shots that demonstrate why it couldn't be there any more. Be aware that a new sidewalk poured over the old one, or poured where the old one was, may only have covered up the mark and rendered it completely invisible and useless. This is not the same thing as destroying the mark. In that case, you can't know whether the mark is still there or not, even if something where it should be talks to your metal detector. And if you can't know, it's Not Found.
In the case you mention, the removal of an entire building, a few photos with information about position from which taken and direction in which camera is aimed, might be sufficient for this site.
For the NGS, the standards are fairly stringent, and it can be useful to add to the above some information from the local building or zoning officials, who can tell you, if you can find them, when such and such a building was taken down.
Destroyed marks are reported to NGS in e-mails to Deb Brown, not on the recovery form.
-
Sometimes these non-NGS marks are in online databases maintained by states and even counties. This doesn't help with logging the mark here, but if you want more detailed information about the mark itself, you can try the state and county where this mark is located. Of course there are still plenty of areas where the records are only on paper in a DOT or county surveyor's office. We have no experience pursuing things into such dens as those, but our little collection has several marks in it with info from state and county websites. Quite a few of us log these marks on the Waymarking site.
Cheers,
-
As always, fabulous and beautiful work. Many thanks.
-
In datasheet descriptions, the term "standpipe" usually denotes a cylindrical water tank set directly on the ground, without legs. They were used as stations to be observed, not occupied, and since the ascendancy of GPS, professionals don't use them any more. The NGS is no longer interested in hearing about them if they are in good condition. If their destruction can be documented, NGS will gratefully remove them from the database. Of course as long as they are in the database here, we suppose they continue to count, if you're counting.
-
Splendid. A joy to read and to look at. Thanks!
-
U.S. Geological Survey disks are very rarely included in the National Geodetic Survey database. A second point to bear in mind is that PIDs almost never coincide with stampings or designations. In other words: there's probably no PID for this particular mark, but if there were, it would be in the database, not on the disk.
-
Tough to say. We can't tell from your posting how you located the object you photographed. How many of the reference items remain? Were you able to take any of the specified measurements? The coordinates are scaled, and therefore not tremendously helpful. According to the current NGS data sheet, a professional survey team reported in 1999 that they could not find the mark. By the way, what is the darker gray rectangle in the center of your photo?
-
edit: m&h, I see that your geocaching.com stats were shown as zero. It turns out that the ampersand in your name was causing problems. That has been corrected and the stats have been updated.
Thanks!
-
As always, we're grateful and awestruck.. This time, though, we're having to guess that your update doesn't include Geocac listings.
Cheers,
-
We encountered data sheets for buried-bottle monuments in 2005, when we were looking for marks on the island of Nantucket. Few of them have been recovered, none by us, but the reason has more to do with the surface than the buried bottles, which may in some cases still lie undisturbed. Nantucket has always had a shifting shoreline, and development there has verged on the irresponsible, so a stake in a dune with a tack in the top of it is not likely to have endured since 1875.
It’s interesting that, as old as these marks are, there was in some cases enough information about them to enable calculation of adjusted coordinates. One or two of these now plot offshore, thanks to beach erosion.
A good example is LW4177, which is now perhaps further inland than it was when placed. The original description is interesting for its use of a movable reference point. We might add that the dwellings in the vicinity of the coordinates are no longer small.
LW4177'DESCRIBED BY COAST AND GEODETIC SURVEY 1875 (JAS)
LW4177'STATION IS ON THE BLUFF DIRECTLY IN RANGE WITH BUG LIGHTS, WHICH
LW4177'ARE BETWEEN THE FOOT OF THE BLUFF BELOW THE STATION AND THE SHORE.
LW4177'THE BUG LIGHTS ARE IN SMALL BUILDINGS ON WHEELS AND ARE DESIGNED
LW4177'TO BE SHIFTED AS THE CHANNEL CHANGES. THE SURFACE MARK IS A STAKE
LW4177'WITH AN ORDINARY WIRE NAIL IN THE HEAD, THE NAIL IN THE STUB
LW4177'BEING 21 METERS (69 FEET) FROM THE NE CORNER OF A SMALL DWELLING
LW4177'AND IN RANGE WITH THE E SIDE OF IT. THE UNDERGROUND MARK IS A
LW4177'BOTTLE EMBEDDED IN EARTH 3 FEET BELOW THE SURFACE OF THE GROUND,
LW4177'IN AN UPRIGHT POSITION.
LW4177
LW4177 STATION RECOVERY (1949)
LW4177
LW4177'RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1949 (ERM)
LW4177'STATION NOT RECOVERED. ORIGINAL POSITION OF BUG LIGHTS CHANGED.
LW4177
LW4177 STATION RECOVERY (1955)
LW4177
LW4177'RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1955 (EHK)
LW4177'STATION NOT RECOVERED. ALL REFERENCES ARE GONE. UNDERGROUND
LW4177'MARK IS PROBABLY BURIED DEEP IN THE SAND AND LOST.
-
Did you notice what agency set the mark? That is, what entity's name was incised around the outer edge of the disk? It could be among the thousands of US Geological Survey disks that aren't in the NGS database. However, there are some features of the stamping that make us think this could be a tidal bench mark set by the National Ocean Service/NOAA. The stamping you provide seems not to appear among the tidal bench marks listed for Woods Hole. Those seem mostly to be on the laboratory grounds. Tidal Bench Marks have their own database, though several of them also have NGS PIDs.
See http://tidesandcurrents.noaa.gov.
Cheers,
-
We use a Filemaker database for our benchmark finds. The form needs a little tweaking, as for example in resetting tab order, so it's not really in shape for sending out. But we figured out what data sheet info we wanted on it, and added a comment box and four photo boxes. We usually don't have more than two photos, but once in a while something comes up, and the form has to be ready for it. We set up the form so that in form view the whole thing is visible in a laptop screen.
We just entered the form-design page and went through a few data sheets. We're still learning the program, so many of its capabilities remain for us to discover.
A potential issue is file size, we guess, but we have just over 200 records in just under 300 mb.
, so we figure you actually know that there's a good reason, not a mere excuse. Off-center punch marks are probably more plentiful than on-center punch marks. The point is surveyed, the pipe driven and capped, and then the precise point is measured again and found to be not in the exact center of the disk. They punch it where it is.
Braille benchmark disc?
in Benchmarking
Posted
GEO--
The issue in the above posts is not that your instruments can't get you to the same point twice, though that is indeed a matter of skill, delicacy and steadiness. It is rather that, once the point has been located, it is a very great physical challenge to drive a pipe into the ground and put a cap on it, such that the very center of the cap is exactly at the point you located. Same goes for disks in drill holes, or even in wet concrete.