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survey tech

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Everything posted by survey tech

  1. Its true that in most localities there will be one year, or a few years, when most markers were set, because the work progressed across the country area by area. Generally, the progress was from east to west, so there will be fewer very old ones, pre-1900, in the west. In my observation, there was a surge of surveying activity in rural areas during the 1930s, when people were put to work on government projects during the depression. There was another surge, mostly in urban and suburban areas, during the 1950s & 60s, due to the post war development boom and the creation of the interstate highway system under President Eisenhower. Reduced government funding and changing technology have acted to limit the number of new stations created since then. Due to CORS technology, there will be even fewer created in the future, making the survivors all the more important in historical terms.
  2. The cairn probably was taken apart and put back up, perhaps a number of times over the years, when surveyors needed access to the point, but it would likely be a lot of work, so I would not recommend it. They had crews of several men who could do it fairly quickly and easily in those days, and the point may also have been left deliberately uncovered for a while when it was in frequent use. Of course, taking it apart and leaving it scattered now would be a disgrace and should not be a legitimate option.
  3. Zhanna Stamping and coordinates are not relevant for a true benchmark such as the one you found on the bridge abutment. The elevation or altitude is the one aspect of such a marker that has significance. As long as its still solid, and its setting remains unmoved, its as good as ever. So your find is as valuable today as the day it was set. I especially appreciate your dedication to finding all the oldest ones in your area, well done.
  4. The stationing number is a calculated point along the linear road alignment base line, which would be shown on plans, but is not likely to be physically marked, so its of little or no help without the plans. NBL stands for north bound lanes. So its somewhere along the north bound base line, probably in an area off limits to pedestrians anyway. (Never mind, EC beat me to it.)
  5. It appears that modern surveying techniques were used to attempt to recover the original marker, resulting in a positive determination that it is gone. Yes, it would have been one of the very oldest had it survived.
  6. Heliotropes and selenotropes were used in geodesy as superior long distance targets, with particular frequency in the southwest, due to the clarity of the atmosphere.
  7. Its not only illegal to park along an interstate unless you are experiencing an emergency, its also illegal for pedestrians to enter the interstate right-of-way, so you can be detained even for just walking along the interstate. The reason for this is that some drivers may be distracted by the sudden and unexpected appearance of a pedestrian, causing them to lose concentration on driving and resulting in a crash.
  8. Thats right, it has never been changed. It was intended to be severe, as $250 was a tremendous sum 100 years ago, but now its little more than a slap on the wrist. Congress just never has time to get around to it.
  9. The number given on the topo is typically the elevation to the nearest whole foot. The name or designation is sometimes given, but the PID never is. You could list all markers in your area by PID and then search through that list for one with an elevation that matches the one on the map when rounded to the nearest foot.
  10. NGS is within NOAA, so when you tell NGS you are telling NOAA.
  11. They had to know the elevation.....because its there.
  12. Its always been my understanding that they place spot elevations where they are most recognizable and useful, at more or less regular intervals, so there will be no large areas without any. Road intersections are typically the most recognizable spots in remote areas, but where a winding road runs for a long distance with no intersections, the bends in the road may be used instead. I think you are doing an outstanding job of pursuing this, and there is a good chance you are right about that spot elevation being on the concrete. I would doubt that you will find a disk there though.
  13. As far as I have been able to decipher, there are those who see some sort of government conspiracy, cover-up or major blunder in the fact that the difference in latitude, from the northern to the southern extents of the Fifth Principal Meridian region, and the difference in longitude, from the eastern to the western extents of same, do not precisely match the theoretical distance in miles that one gets when one adds up the total number of sections or townships in that region, even after correction for curvature of the earth is applied. Efforts to explain that no such relationship can realistically be expected, have thus far proven futile.
  14. An azimuth is a means of describing a direction. It nust employ some arbitrary line of reference to have any meaning. In land surveying, that line of reference has always been due north. Azimuths measured off that line are described as right north azimuths or left north azimuths, depending on whether they are measured clockwise or counter cloxckwise, respectively, clockwise being the norm. Geodetic azimuths, however, were formerly measured off an arbitrary reference line running due south, also right or left, as the above. Modern adjustments of geodetic data, since the major readjustment of 1983, have switched to right north azimuths, presumably to reduce confusion. This is in the northern hemisphere, in the southern hemisphere the reverse is the case.
  15. A tri-station atop Half Dome would have been superb for mapping 100 years ago, but now that the mapping of the park is all long completed, there would be no use for one there, since the park is, and shall remain, free from development, now and forever.
  16. They may have been marking something other than property lines. Surveyors lay out all kinds of structures, easements, setbacks, etc., so its impossible to tell what they are doing, or why they are doing it, without inquiring. Next time just ask for an explanation, if they have time they will probably be willing to explain what they are doing, how and why. If its your property, and you think something is being done wrong, you have the right to question it.
  17. Not all things are what they appear to be. If you find something 10 miles away from where it was supposed to be, you are probably finding something entirely different. The great majority of errors in the data are clerical in nature, such as typos, due to the massive amount of data that has been processed, and not the result of the survey data itself, which except for the most remote points, has been used and checked many times down through the years. Points listed in the wrong county, and other similar office blunders, not related to the actual mathematical data, are usually just ignored by surveyors, since they are so obvious that they are not likely to cause any problems for professionals who generally already know where the points in their work area are.
  18. Thats right, if you look exactly half a mile either due east or due west, assuming you are in an undeveloped area, you will find others similarly marked, the northeast and northwest corners of section 31 in that particular township. These are cadastral markers, not geodetic markers, though very similar in appearance and markings, right down to the $250 fine.
  19. You will find a great many sites like this, with remains of old surveys, in the west, where the wide open spaces are ideal for both long distance visibility on the ground and aerial mapping as well. Those in the east will rarely if ever find such a site. The fact that it took three hours off road to get there is the reason that the target pole is still there. They went to the trouble of settting it up that way so they would not have to visit the spot again to retrieve any equipment.
  20. The cairn is probably centered over the original point. The signal pole is intended to be directly over the spot, serving the same purpose to the surveyor as a tower or spire, which is a good long distance target. Its probably not extremely precise by modern standards, but in the old days, being within a fraction of a foot was considered relatively precise. Cairns last a long time in the southwest if well built. Many of them gradually become well known among the locals and being often visited, a trail is gradually formed, which encourages more people to hike that route, and a hking trail eventually develops. The cairn then becomes a landmark on the trail and some regular hikers of the trail take up the responsibility of maintaining it. Some also bring a stone of their own to add to it. Thus the more fortunate cairns are kept in good shape and some even grow
  21. Cannot see your pictures, but I would guess they are right-of-way markers, probably set by the state. If so, they would define the lines between public r/w and private land. This would be especially likely if one or both of the roads are state highways and/or if road widening is being done there. Not a stupid question at all, these things are mysterious to most people. Such points would not be in the NGS database.
  22. North Carolina is not a Public Land state, so USGS mapping is not likely to help. The property owner must have some idea of his boundaries, although it would be a good idea to also check with the surrounding property owners, to make sure they are all in agreement about where their boundaries are. Better to take the time to check now than get shot later.
  23. Very nice, the vista is excellent because this spot was chosen for its visibilty from great distances in several directions, making it an ideal point in the triangulation network. Arizona has a good many remote, well preserved, old points, compared to most other states. Points such as this were instrumental in the monumental task of mapping the Grand Canyon.
  24. Originally, the main purpose of geodetic surveys was mapping. In modern times, engineering design has become an equally important use of the geodetic markers and data. Whereas the Public Land system is a property boundary system, whereby property lines are determined, developed in order to efficiently parcel out the Public Land to individual owners, known as entrymen. It was intended to eliminate the chaos resulting from the absence of any such system in the colonial states. Mathematical connections are sometimes made by surveyors between the two systems for various reasons, and the science known as GIS, Geographic Information Systems, will combine the information from both systems in the future, but the two are separate and distinct in their origins and purposes.
  25. Thats correct. Also, a red "+" symbol shown at the intersection of the red lines indicates a section corner that was found at the time of the mapping. While some states do share initial points, most Public Land states have their own initial point, completely unrelated to any of the others. The first Public Land state was Ohio, not Louisiana. All of this, however, is completely unrelated to geodetic surveying, which is a different branch of the surveying profession and serves an entirely different purpose.
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