Permanent benchmark definition1/15/2024 ![]() ![]() In the U.S., survey marks that meet certain standards for accuracy are part of a national database that is maintained by the National Geodetic Survey (NGS). Occasionally, these buried marks had surface marks set directly above them. Some old station marks were buried several feet down (to protect them from being struck by ploughs). Reference marks also made it possible to replace (or reset) a station mark that had been disturbed or destroyed. These reference marks made it easier for later visitors to "recover" (or re-find) the primary ("station") mark. A triangulation station was often surrounded by several (usually three) reference marks (see second photo at left), each of which bore an arrow that pointed back towards the main station. It was often marked by a "station disk" (see upper photo at left), a brass disk with a triangle inscribed on its surface and an impressed mark that indicated the precise point over which a surveyor's plumb-bob should be dropped to assure a precise location over it. For example, in triangulation surveys, the primary point identified was called the triangulation station, or the "main station". Geodetic survey markers were often set in groups. Such surveys laid the basis for map-making across the world. Survey markers were often placed as part of triangulation surveys, measurement efforts that moved systematically across states or regions, establishing the angles and distances between various points. Survey markers in Nagoya, Japan, which bear stylized images of shachihoko, are noted for their elaborate design. These marks are intended to be permanent, and disturbing them is generally prohibited by federal and state law. Today in the United States, the most common geodetic survey marks are cast metal disks with stamped legends on their face set in rock ledges, embedded in the tops of concrete pillars, or affixed to the tops of pipes that have been sunk into the ground. In the 19th century, these marks were often drill holes in rock ledges, crosses or triangles chiseled in rock, or copper or brass bolts sunk into bedrock. Some markers have been used to designate tripoints, or the meeting points of three or more countries. Horizontal position markers used for triangulation are also known as triangulation stations.īenchmarking is the hobby of "hunting" for these marks.Īll sorts of different objects, ranging from the familiar brass disks to liquor bottles, clay pots, and rock cairns, have been used over the years as survey markers. ![]() A benchmark is a type of survey marker that indicates elevation ( vertical position). They are used in geodetic and land surveying. Survey markers, also called survey marks, survey monuments, or geodetic marks, are objects placed to mark key survey points on the Earth's surface. Coast and Geodetic Survey marker Corp of Engineer Survey Marker Marker for triangulation station, indicated by triangle in center Reference marker for triangulation station in upper photo A cotton spindle spike in Tel Aviv pavement, used as a marker for public area cadastral surveying. ( September 2022) ( Learn how and when to remove this template message)Ĭloseup of a U.S. You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate. The examples and perspective in this article may not represent a worldwide view of the subject. ![]()
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