Survey marker

Bronze disc set in concrete — Marker for triangulation station, indicated by triangle in center

Bronze disc with inscribed arrow, set in concrete — 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.

In surveying and geodesy, a marker (also called a mark, monument, or station) is an object firmly installed to indicate points on the Earth's surface with known coordinates. A benchmark is a type of survey marker that indicates elevation (vertical position). Horizontal position markers used for triangulation are also known as triangulation stations. A set of interrelated geodetic markers form a geodetic network. An active station or reference station is occupied permanently with a measurement instrument, such as GPS/GNSS continuously operating reference stations (CORS). Benchmarking or trigpointing is the hobby of searching for these marks.

A USGS bench mark disk embedded in bedrock at 37°10'45.3"N 86°06'32.0"W, Mammoth Cave National Park, Kentucky; the blank elevation field and "Write the Director, Washington D.C." inscription indicate a late 19th or early 20th century marker, predating standardized pre-stamped survey disks.