{"id":5077,"date":"2015-07-25T04:30:22","date_gmt":"2015-07-25T09:30:22","guid":{"rendered":"http:\/\/gisgeography.com\/?p=5077"},"modified":"2025-03-29T08:44:52","modified_gmt":"2025-03-29T13:44:52","slug":"survey-benchmark-monument-location-geocache","status":"publish","type":"post","link":"https:\/\/gisgeography.com\/survey-benchmark-monument-location-geocache\/","title":{"rendered":"Survey Benchmark Monument Locations"},"content":{"rendered":"\n
\"Geodetic<\/figure>\n\n\n\n
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What Are Survey Benchmark Monument Locations?<\/h3>\n\n\n\n

Survey benchmark monuments are brass or metal disks in the ground that provide latitude, longitude<\/a>, or orthometric height.<\/p>\n\n\n\n

They give surveyors a point of reference because they use them as part of a set of survey observations.<\/p>\n\n\n\n

Some benchmarks also provide a reference for elevations. These types of benchmarks indicate the height above or below sea level at that location.<\/p>\n\n\n\n

A “benchmark”<\/em> is a generic term sometimes referred to as survey marks, geodetic marks, and control stations<\/strong>. Each has a slight difference in meaning<\/a>.<\/p>\n\n\n\n

However, survey professionals prefer the terms station<\/strong> or mark<\/strong> rather than “benchmark” to describe horizontal control marks.<\/p>\n<\/div><\/div>\n\n\n\n

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Developing a Datum Using Triangulation<\/h3>\n\n\n
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\"Geodetic<\/figure>\n<\/div>\n\n\n

Example of a survey benchmark monument. More recently, surveyors have used markers to set up a GPS receiver antenna in a known position for Differential GPS surveying.<\/p>\n\n\n\n

In surveying and mapping large areas, surveyors must take into consideration the curvature of the surface of the Earth and sea-level surface. This is why geodesists developed the geodetic survey network extending across North America. They serve as a basis for North America\u2019s horizontal control data.<\/p>\n\n\n\n

With 2 benchmark locations, surveyors use triangulation and trigonometry to measure the direction, distance, and elevation between them. Geodetic leveling<\/strong> can help understand the area and volume of the Earth.<\/p>\n\n\n\n

Horizontal control data provide a rigid framework for map makers, engineers, and land surveyors in North America. It makes it possible for greater precision for surveys and to locate national, state, county, and private boundaries with greater precision. Benchmarks are important to surveyors because they help accurately measure the positions of all land boundaries and modern infrastructure.<\/p>\n<\/div><\/div>\n\n\n\n

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Who is Responsible for Survey Benchmark Monuments?<\/h3>\n\n\n\n

In the United States, NOAA\u2019s National Geodetic Survey (NGS)<\/a> is responsible for managing approximately 240,000 stations<\/strong> gathered over the last two centuries. The National Geodetic Survey Data Explorer<\/a> makes this data available to the general public.<\/p>\n\n\n\n

NGS developed the North American Datum of 1927<\/a> which used the Clarke spheroid of 1866 and a point of origin at Meade’s Ranch. Then, NGS developed the more accurate North American Datum of 1983 (NAD 83)<\/a>. The United States, Canada, Mexico, and Central America use this horizontal control datum based on a geocentric origin and the Geodetic Reference System 1980.<\/p>\n\n\n\n