survey tech

All tri-stations have names, so try searching for it that way. If its not in the database it was either misfiled or its not a tri-station. Not all disks with a triangle symbol are tri-stations, the disks are sometimes used for other purposes.

Such notation indicates that the point was used at night. The light was the target set up over the point. The reason for mentioning it is so that others will know what conditions they may expect to have to deal with when they use the point in the future. The higher the light, the more obtacles, usually trees or buildings, are likely to be near the point.

Various countries may be less inclined to provide free public access to their data than the US, but all but the most primitive must have some form of control network without which mapping would be impossible, so its a matter of determining whether or not the data is available to the public in your country.

You would be looking for an antenna, about the size of the proverbial bread box, usually in a dome shaped or cone shaped housing to protect it from the elements, typically mounted on a high building with 360 degree visibility, often in a secure area, such as an airport, easy to spot from a distance, but for obvious reasons difficult to get close to. There are currently about 2 dozen in your state of Texas.

Excellent examples. The stem is made thicker and stronger than the disk in order to defeat any attempts to pry the disk out of its setting. Under enough pressure the disk will crack and break, disappointing the vandal, and leaving the stem and the remainder of the disk in place.

All the above comments are correct, except where Rog says that a tower is not a control point. It is a control point, known specifically as an intersection station, because it was created by intersecting lines and cannot be physically occupied by an individual with surveying equipment.

The fact that there is no elevation stamped on the disk does not mean that the benchmark has no elevation. In fact only a small percentage of all benchmarks have the elevation stamped on them. It has been found in recent years that stamping the original elevation on the disk can cause problems, since elevations can change due to adjustments, so the practice of stamping elevations was dropped.

I agree that this area of history can be very interesting. In fact, there are several other state boundaries that have also been the source of long running litigation and some have been resurveyed many times over, which usually only results in even greater confusion, such as California/Nevada, Texas/New Mexico, Texas/Oklahoma, Tennessee/Kentucky, Tennessee/Georgia, New Hampshire/Massachusetts, New Hampshie/Maine and others.

King county has one of the most extensive control nets in the country. A lot of them may be gone, but there are still enough to keep you hunting for years.

The NGS uses the word recovered in the sense that any marker, having been put in place and left to the mercy of fate for some length of time, must be visited and seen to confirm that it has survived. It is not intended to imply that the marker has been removed, although it is understandable that people are often confused by this use of the word recovery. I have never heard of a marker being retired. If the information pertaining to a particular marker is determined to be inaccurate, the coordinates and/or elevation data is adjusted or revised, but the marker is left in place.

I imagine your concrete pillars are the equivalent of our tri-stations, which were also set using trigonometry.

If you are saying that they are running parallel to the road, and they are all the same distance from the road, then they are probably a type of right-of-way marker. If the numbers on them are all different, then that number is probably just a computer point number, although it is unusual to find this number stamped on a point. If the number includes a decimal point, it could be the elevation of each point in either feet or meters.

This is an entirely different use of the word reset. In boundary surveying, which is at issue in this example, the goal is always to reset the point in question at the original location or as near as possible thereto. In geodetic surveying, however, there is no reason to reset the point in the same place if it is not convenient to do so, and therefore that is seldom done. Sadly, this is a good example of why many surveyors justifiably fear the publicization of historic or unique points, since it does often attract the unwanted attention of vandals.

I know from personal experience that it is possible to prevent at least some inadvertent destruction of benchmarks, though obviously not deliberate destruction, through increased awareness of the significance of such points. Particularly in cases where property owners are unaware of the presence of markers on or near their land, informing them can often increase their respect for the points, turning them into protectors rather than potential destroyers of the markers. On the topic of national security, although GPS does have military applications, I have to agree that only pananoid conspiracy theorists and other such outriders on the lunatic fringe could be foolish enough to imagine that benchmarks have any relevance at all to our national defense or that benchmark hunting poses any threat whatsoever to our national security.

Sounds like very recent points, bearing the id # of the land surveyor. They will probably not appear in any national database.

Try searching a small radius centered on the oldest institution in a given community, typically a courthouse, church, school, etc. Also focus on old rail lines, as many long bench level runs followed these routes in the early days, and development has often bypassed them, so many of the oldest markers are along old railways or what remains of them. Where they have been turned into trails or greenways, however, the markers will usually be gone.

Benchmarks in rapidly developing areas seldom survive long. One of the many tasks of the surveyors involved in such projects is to locate any markers that are in areas to be demolished and transfer the coordinates and/or elevation from the doomed marker to a new point or points nearby before the demolition occurs. This is standard operating procedure, so the network is preserved and even multiplied, although the original markers gradually pass away.

Logscaler I appreciate your attitude of understanding and respect for the value of survey markers of all kinds, which is exactly the kind of attitude I have attempted to promote in my messages. I hope geocachers, by sharing the knowledge they have gained through this activity with those they meet along the way, may help to prevent incidents of needless destruction, such as the one you mention. Yes, there are thousands of former markers now serving as paperweights and ornaments all around the country, mostly on the desks and shelves of engineering and surveying professionals. However, these markers were victims of accidental or unavoidable destruction, which is an inevitable aspect of development. This was foreseen by those who began the control network in the nineteenth century. It was anticipated that local professionals would expand the network and perpetuate it by replacing markers, which has indeed occured as expected. So it is not a crime to save a disk found lying amidst construction debris or to remove and keep one that is about to be bulldozed, once it has been replaced, usually by the surveyor in charge of the project. Of course, the removal or demolition of any marker by a private party, such as a homeowner building a new driveway, as you pointed out, without first informing a surveyor or engineer, thereby providing an opportunity for the point to be replaced or an alternative location for the driveway to be proposed, is unfortunate, but not a crime unless done willfully, which is the distinguishing element of vandalism

Broken Arrow You are correct that many brass caps inform the visitor that disturbing the marker is a felony. Im also quite sure you are correct that far more markers are destroyed by construction than by vandalism. However, these facts are irrelevant, since there is no way that one can legitimately compare accidental or inadvertant destruction to deliberate destruction. When a marker is destroyed in the process of building or rebuilding a road, bridge, school, hospital, etc., that is a shame. But when a marker is destroyed because somebody feels like it would make a neat souvenir, that, as you have noted, is a crime. Perhaps the most important contribution geocachers can make to the preservation of our control network is to help reinforce this distinction by sharing their acquired knowledge of the significance of these markers with everyone they meet while benchmark hunting, thereby promoting respect for these points, which represent the accomplishments of several generations of surveyors.

Rusty is right, except where he implies that GPS is making benchmarks obsolete. Surveys, even those done using GPS, are begun from existing benchmarks, checked against other existing benchmarks, and result in the creation of new benchmarks, although relatively few ever reach the NGS database, so those found in the NGS database are still as useful as ever, and will remain so. Unlike property boundary markers, which are set at specific locations, sometimes forming a grid pattern, benchmarks are set at random locations chosen by the project surveyor, primarily for convenience and, if possible, permanence. For example, a concrete culvert is a common setting for a benchmark because its a very solid object, in close proximity to the road, likely to remain in place for years, and therefore very useful for any projects along that road. Church buildings are also often chosen as benchmark sites, since they are usually centrally located, easily accessible, easily identifiable, and less likely than most other buildings to be destroyed during future development. The NGS website assumes the user has some knowledge of surveying and therefore has little fundamental information, aside from that of a historical nature. A conversation with a local surveyor or civil engineer would be the quickest and easiest way to get your specific questions about surveying practices in your area answered in detail.

While there are many cases where a benchmark disk may be set at or near the base of a building or other prominent structure, there would be no point in setting a disk on top of a dome, steeple, water tower, radio tower, smokestack, lighthouse or any other object of that shape. When a surveyor uses a horizontal control disk in his work, he must set up some kind of target directly above it, in order to be able to observe it from a distance. The idea in using these high points as stations, and the very reason they were chosen to serve as such, is because they are already good targets. When a surveyor observes one of these objects through the telescopic element of his instrument from a great distance, often of many miles, it looks like a needle, and therefore makes a perfect existing target, saving him the trouble of visiting the object to set up a target. So anyone attempting to climb one of these things in hopes of finding something on top will be disappointed.

Most markers, particularly triangulation stations, which are usually on or near peaks, already have a discernable trail leading to them, so I would not expect additional damage to the environment, resulting from increased foot traffic to such sites, to be an issue, even in our parks. The idea of placing man-made non-biodegradeable objects in the parks without permission may be a cause for some concern among park officials however.

Lost means gone without a trace and is equivalent to destroyed. Obliterated means gone but some related evidence remains and is equivalent to not found. However, these are boundary surveying terms, which are not typically used in geodetic surveying, so they are not really relevant to benchmark hunting.

BDT The main reason the concept of azimuth marks was developed is due to the fact that most triangulation stations are very far apart and they are usually not intervisible from the ground. So, in order to save local surveyors from having to go to all the trouble of using towers to see from station to station, an azimuth mark was set for each station, at a spot convenient for local visibility. The local surveyor can then set up a surveying instrument on the station and sight down to the azimuth mark and immediately orient his work to the network. You are right that the bearing system of directions, while mathematically identical to magnetic compass directions, is actually an entirely different system, free of magnetic fluctuation, based on astronomic north, as determined by astronomic observations on Polaris and/or the other observable stars. You may also notice that bearing/azimuth directions between points on the NGS datasheets are given in both absolute and grid form. Each portion of each state has its own grid system, based on either Lambert or Mercator projection, used to minimize the distortion introduced by the curvature of the earth. The difference between absolute azimuth and grid azimuth at any given point is known as Theta, which is a function of how far the point is from the center of the projection area. The significance of this, of course, is that surveyors typically work on a surface that is treated as a plane, rather than an arc, so the Theta angle is used to convert from absolute directions to grid directions. Pretty technical stuff, but you asked for it.

I would hope anyone operating without a full understanding of the different types of points would appreciate being educated, rather than feeling insulted. In fact, I suspect they might feel embarrassed after realizing the truth and wonder why no one had advised them about it. I doubt that anyone would prefer to continue acting under a mistaken premise. After all, life is for learning.