![]() ![]() Specific purpose in mind such as 'traverse station', 'triangulation station' (classical horizontal control), 'benchmark' (classical vertical control), etc."Īnyway, hope you find the above information helpful. On the other hand, USC&GS/NGS uses 'monuments' embossed with a With 'benchmark' or 'BM' embossed on the 'monument'. In the comments section of " by Survey1989" I read this " In a nutshell, USGS uses a generic 'monument' type for all its surveys, The guys that make maps, USGS placed survey disks for awhile too. I believe the ational Geodetic Survey did most of the surveying of the USA. NGS defines the official geodetic datums for all federal mapping activities in the U.S. They are set so as to be visible which means often they are at, on, or near the highest point which ever is the most visible. A geodetic datum or reference frame is an abstract coordinate system with a reference surface (such as sea level) that serves to provide known locations to begin surveys and create maps. Survey Disk are not typically concerned with being place on the highest point. Once the primary mark is found and the surveyor sets up his gear in order to make accurate measurements he needs a known point of reference, and that then is the second function of both types of Reference Marks – they allow the surveyor to know the exact direction in which he is looking. First they provide a point from which a surveyor can locate a primary mark. Reference Marks, including Azimuth Marks, serve two purposes. Unlike a normal Reference Mark which is typically located within thirty meters (one tape length) of the primary mark, Azimuth Marks are set typically between one quarter of a mile and two miles from the primary mark, give or take. An Azimuth Mark is a long Reference Mark. A Triangulation Station is a specific type of a control station having had its position determined by measuring distances and angles from other stations. Whereas technically monuments concerned only with horizontal positioning are called horizontal control stations or simply control stations. ![]() For example, a bench mark is a point of precisely measured elevation, but some might call a monument concerned only with horizontal positioning a bench mark since they are both marked with metal disks. There are technical reasons for these names, but surveying is a complex discipline and terms end up being used interchangeably even if not strictly correct. These names might also be proceeded with terms like survey, horizontal control, control, or triangulation – as in “triangulation station”. Coast and Geodetic Survey and, later, the National Ocean Service). Survey marks are known by various other names, such as monuments, points, bench marks, and stations. The first leveling route in the United States considered to be of geodetic quality was established in 1856-57 under the direction of G.B. Reference Marks are stamped in the center with a crossed arrow symbol, and are always set with their arrow symbol accurately pointing toward a primary mark. Disks stamped with an equilateral triangle symbol in the center are horizontal control marks and they pinpoint a spot for which the latitude and longitude has been accurately calculated. Vertical control marks are those for which a measured accurate elevation above sea level has been determined, and they are stamped at the center with a crossed slash symbol. Both types of marks use the same sized disks, made of either bronze or aluminum, and stamped with text, numbers, and a symbol. Additionally other survey marks (non-primary) are disks which point to a primary mark, and these are known as Reference Marks. Here is what my other reading seem to agree on: A primary survey mark is a point on the earth for which an accurately measured location, either horizontally or vertically has been determined. With that said, I think it is worth noting though, that strictly speaking a lot of the metal disks in the photos are not bench marks. Some of it might just be a matter of terms being used colloquially in one situation and formally in another. Great idea, and a fun photo album to look at.Īs I read more and more on this topic of Survey Marks I find again and again that the terms are not defined hard and fast. 5.Vanman798 - 12:50 pm - Hasn't voted Terminology.3.8 A Nonlinear conservation law: shallow water equation in 2D.3.5.2 DG for the acoustic wave equation.3.5.1 Operator applications for Discontinuous Galerkin discretizations - linear transport.3.2 Incompressible Navier-Stokes equations.Symbolic definition of forms : magnetic field. ![]()
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