Survey marker in the context of "Geographical pole"

The International Boundary Commission (French: Commission de la frontière internationale) is a bi-national organization responsible for surveying and mapping the Canada–United States border and regulating construction close to the border. The commission was created in 1908 and made permanent by a treaty in 1925.

Its responsibilities also include maintaining boundary monuments and buoys, keeping the border vista on each side clear of brush and vegetation within three meters (about 10 feet) from the boundary, overseeing any applications for permission to build within the vista, and reporting annually to the governments of both countries.

A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical direction as a reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical datum. It is typically made of stone, wood, or lead, but can also be made of other metals. If it is used for decoration, it may be made of bone or ivory.

The instrument has been used since at least the time of ancient Egypt to ensure that constructions are "plumb", or vertical. It is also used in surveying, to establish the nadir (opposite of zenith) with respect to gravity of a point in space. It is used with a variety of instruments (including levels, theodolites, and steel tapes) to set the instrument exactly over a fixed survey marker or to transcribe positions onto the ground for placing a marker.

The North American Datum (NAD) is the horizontal datum used to define latitude and longitude (horizontal coordinates) in North America. A datum is a formal description of the shape of the Earth along with survey markers serving as "anchor" points for the coordinate system. In surveying, cartography, and land-use planning, two North American Datums are in use: the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83). Both are geodetic reference systems based on slightly different assumptions and measurements.

Vertical measurements, based on distances above or below Mean High Water (MHW), are calculated using the North American Vertical Datum of 1988 (NAVD 88).

The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future. These marks were usually indicated with a chiseled arrow – specifically a broad arrow – below the horizontal line. A benchmark is a type of survey marker.

The term is generally applied to any item used to mark a point as an elevation reference. Frequently, bronze or aluminum disks are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point. If an elevation is marked on a map, but there is no physical mark on the ground, it is a spot height.

Benchmarking, also known as benchmark hunting, is a hobby activity in which participants find benchmarks (also known as survey markers or geodetic control points). The term "benchmark" is used only to refer to survey markers that designate a certain elevation, but hobbyists often use the term benchmarks to include triangulation stations or other reference marks. Like geocaching, the activity has become popular since 1995, propelled by the availability of online data on the location of survey marks (with directions for finding them) and by the rise of hobbyist-oriented websites.

In 2022 Geocaching HQ informed that they will remove Benchmarking from the Geocaching.com website.