bench mark

Well-defined, uniformly fixed point on the
land’s surface that is used for a reference point from which
other measurements can be made. It is generally marked by a
circular bronze disk with a 3.75-inch (10-cm) diameter
embedded firmly in bedrock or other permanent structure. In
the United States, bench marks are installed and maintained
by the U.S. Coast and Geodetic Survey and by the U.S. Geological
Survey. The elevations of many benchmarks were in
the past established by a surveying technique called differential
leveling. Now it is more common to determine elevations
using satellite-based differential global positioning systems.
Bench marks are marked on topographic maps using the
abbreviation B.M., and they are used for determining elevation
and for surveying and construction
Post a Comment

Post a Comment