Fixed point in geodesy a survey point is called, which fulfills the two following conditions:

• The point is coordinatively well-known from a preceding measurement (situation and/or height)
• The point is durably marked out in nature (stabilizes).

Depending upon that, which coordinates of the point are indicated, one speaks of a Lagefestpunkt, a or a combination of both. The determination of the coordinates must have taken place via a measurement (not graphic). In addition geodetic methods can, like e.g. Government inspection department measurements, net measurements, polygonal traverse drafts or methods of single-point determination used its. A can have been determined also by a leveling.

The coordinates and/or heights of the points are stored for the later use in further measurement work in a fixed point file.

Stabilization

The stabilization of the fixed points takes place in very different kind, which of the ground condition, which necessary durability and on legal questions depends. Frequent methods of stabilization are:

• Stake (usually 4x2 cm 50 cm long) with nail, particularly within the range of building sites uses
• Steel tube with 8 - 50 cm length, 16 or 22 mm in diameter, usually with red plastic cap
• Metal mark (metal plate with shank, 20 - 40 cm long)
• Plastic mark (plastic plate with shank, 30 - 60 cm long)
• Natural stone, particularly for boundaries
• Behauener stone (at the best granite or cast stone (12 x 12 x 50 cm or 20 x 20 x 60 cm with eingemeisseltem cross
• "“Bitumen nail"” (large nail or pin with Schaftdurchmesser of approx. 0.5 cm, head diameter 1 - 2.5 cm, 5 - 15 cm long)
• "“Cross in the rock"” (Eingemeisseltes Kreuzzeichen in natural rock)
• "“Carrots"” (plastic or clay/tone cones)
• Tower or elevator pin for (brass pin with 15 cm length and 3 cm diameter, in church tower or Hauswand, e.g. grooved, immured).

With fixed points of the official land surveying the expenditure is higher for stabilization, in order to avoid a damage or a distance of the point and a necessary new measurement:

• Several stabilization are brought mm-exactly centrically one above the other into the soil - e.g. a steel tube, over it a clinker plate and zuoberst a cast stone
• Additionally to the actual point in the distance from some meters to decimal meters "“points of insurance"” are marked out, which are likewise coordinate-moderately determined. In case of the loss of one point these can be used as replacement and/or for the re-establishment of the lost point.

Documentation

Nearly everyone in the soil of marked out fixed points is covered after some time to over-grow or by earth and/or sediment. In order those provided exactly and cost-intensively fixed points even after longer Nichtverwendung again to find, to documentations over them are made:

• Description of point or Punkttopografie: Sketch of the direct environment of the point. It contains salient elements, which remain unchanged in all probability in next time, above all of buildings, larger trees and edges of road. To some these elements clamping mass are measured, in order the point also some centimeters underground or grass scar to find to be able (with road construction or by winter dispersion to be able fixed points to 20 cm into the depth "“to come"”). These descriptions of point are administered (on paper or in digital form) in a fixed point card index.
• Fixed point overview: Over the fixed points some km of a large area a general map is provided, in which the points are marked by small circles as exactly as possible 0.3 mm). Depending upon size of the area and solidity of the points the point overview has yardsticks between 1:5.000 and 1:50.000.

Articles in category "Fixed point (geodesy)"

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