Elevation network
In geodesy, an elevation network is understood to be a surveying network whose points only show the heights above sea level, but not the horizontal coordinates . The position of the points is generally only recorded on a sketch ( point description ) or a plan.
The points form the basis for height measurements of further points. Their demarcation takes place - similar to the three-dimensional control points - through metal marks in the soil by the tower bolts on buildings or (more rarely) by frost introduced in the floor stones. A systematically laid out, area-wide elevation network for an entire country is called an altitude fixed point field.
Measurement methods
The basic network of official height networks is mainly determined by precision leveling . Its grid-shaped lines are laid out at intervals of about 50–100 km (see picture above). They run along higher-level transport networks (railway lines, roads) and have an accuracy of a few tenths of a millimeter . The calculation from the measured height differences - or from additional GPS leveling - is carried out through network adjustment .
Densification networks are inserted into this basic network of precise intersections , the points of which are approximately kilometers apart, even closer in built-up areas. In addition to leveling, trigonometric height measurement is also used here.
The heights above sea level ( geoid ) in Central and Western Europe refer mainly to sea level (Amsterdam) or to the levels of Marseille , Turin or Trieste . Your theoretical basis can be orthometric heights (physical level surfaces) or normal heights (with regard to quasigeoid ).
See also
- Height measurement
- Above sea level
- digital elevation model
- United European Leveling Net
- Communicating tubes
literature
- Bernhard Heck: Calculation methods and evaluation models for national surveying . Wichmann-Verlag, Karlsruhe 1987 and 2003.