Switch-on point
In surveying, switch-on points (EP) are a close-knit network of fixed points , which, however, have a somewhat lower accuracy than a trigonometric point .
Switch-on points were mainly measured terrestrially (with theodolites ) until about 1970 by laying a grid of polygons along subordinate traffic routes ( side streets , driveways , etc.) . Later it was for reasons of economic efficiency on the method of aerial - photogrammetry over. At medium altitudes, it delivers accuracies of 1 to 3 decimeters, while terrestrial (with greater effort) a few centimeters can be achieved.
The demarcation of the EPs is performed in urban areas predominantly by:
- Iron pipes with protective caps, special nails (in different materials)
- Bolts in the ground or in walls
- Fork points (double marks on walls)
- occasional stone marks (e.g. in green strips)
- isolated chisel cross , rock cross.
In rural areas especially:
- Iron pipes (often with a wooden stake to make it easier to find)
- Stone marks (in the manner of boundary stones )
- Pole signals (5 to 10 cm thick, 3 to 5 m high metal tube with high-contrast target mark)
- occasional wooden pegs
- and combined marking with height bolts .
The average distance between EPs is 200 to 500 meters (in Austria around 300 m), but the creation of new EP networks is no longer necessary due to the increasing use of GPS and dGPS .
See also: Fixed point field