Other Types of Survey Marks
Triangulation points, also known as trig points, are marks with a precisely established horizontal position. These points may be marked by disks similar to benchmark disks, but set horizontally, and are also sometimes used as elevation benchmarks. Prominent features on buildings such as the tip of a church spire or a chimney stack are also used as reference points for triangulation. In the United Kingdom, triangulation points are often set in large concrete markers, which as well as functioning as a triangulation point, have a benchmark set into the side. With the increasing use of GPS and electronic distance measuring devices, the same techniques and equipment are used to fix the horizontal and vertical position of a survey marker at the same moment, and therefore the marks are usually regarded as "fixed in three dimensions".
Read more about this topic: Benchmark (surveying)
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