Benchmark (surveying)
A survey point or short measuring point is a stable in the ground or on a building marked point, the geodesics serves as the starting point or destination of surveys.
However, the term is not uniformly defined. Part of it is close in the sense understood by the fixed point: A position and / or in terms of height and certain usually permanently fixed point, connect to the itself topographic data collection, engineering or land surveying.
Survey points are calculated as the Trigonometric point ( TP) by means of triangulation. Height of fixed points are determined by geometric leveling.
Survey point in the sense of fixed point
Survey points are distinguished by fixed points of the position, height and gravity of fiducial points. For ground control points (LFP ) coordinates are calculated in a location reference system and they are mostly suitable as installation point for a surveying tripod with theodolite. Height of fixed points (HFP ) are used for determining elevations above sea level while for gravity control points (SFP ) data refer to measurements and gravity are calculated.
With the increasing importance of GPS surveying these formerly separate fixed-point fields, more and more suitable Vermarkungen to three-dimensional fixed points. A line of sight over a long distance is not required now.
Overview of the survey points since 1820 resulting in Germany
- Geodetic ground control points of land surveying - with stable above and underground demarcation and typical position accuracies of 1-5 cm particular points of a triangulation (definition, a plate and TP- pillar), the measurement pillar panel with signal
- Particularly marketed Nivellementpunkte ( such as masonry bolts (MB) or height marks (HM) churches ( mostly on the church tower ), train stations (usually the side of the track ) )
- Such as technical control networks, measuring consoles, First points in the mine or tunnel
Other stable marketed survey points
In the language of most surveyors are among the survey points also
- Well certain controlled " points of detail " that are clearly defined and stabilized on buildings or limits - for example house corners, wall and border points
- Well certain immovable points in nature - for example, marks on rocks or large blocks in geodynamics measurements on mountain slopes or glaciers
- Soil marks in the solid road surface or on sidewalks - mostly bolts or nails with the inscription " survey point " or " measuring point "
- Schraubmarken or stable embarked pegs, if possible with reference peg or protective scaffolding
- Other permanent marketed points
Height fixed point ( landmark ) in a forest in Berlin- Spandau
Survey point, this version is also called " Ulmer cover ".
Triangulation Gisliflue, Jura / Switzerland, 772 m above sea level
Historical height mark ( Bad Saulgau - Church of St. John )
Height brand " Royal Prussian land survey " (height not more readable) at the church in Siebleben
Height brand " Royal Prussian land survey " in Stradaunen, Masuria
Surveying storm sketch
Points and units of measurement in database
In the era of IT, the survey points are verspeichert in almost all work in databases. Beyond providing the name and coordinates, if possible, the " genesis " and the context of the points is noted, so that the exact location of each survey point can be updated based on new measurement data at any time. Such measurements are mainly:
- Cuts with rays ( directions) and distances ( distances), so most forward section and Resection
- Polar points ( direction distance )
- Lock dimensions (control distance ) between points, definition of circular arcs, etc., and
- Traversing (polygon ) and Resection for establishing points of the theodolite
In geographic information systems, individual elements are often associated with survey points to perform, for example, a transformation of local coordinates in a parent frame of reference. The information, on which points such links exist, is usually stored in the geometry of the GIS element.
' See also: Lookout, eccentric, geodesy, high level, steeple, power first-order control point, plumb, Struve Geodetic Arc, triangulation ( geodesy), Survey Office, centering