Altitude points (use heights)

Wherever precise height specifications are required, height fixed points have always been used for surveying tasks and solutions in the context of construction surveying, map production and land surveying. The height fixed points serve in their entirety the physical realization of the height fixed point field and thus the height component of the geodetic spatial reference within the meaning of § 2 paragraph 2 of the Hamburg Act on Surveying (HmbVermG) of 20.04.2005 (HmbGVBl. 2005, p.135). in the field of the Free and Hanseatic City of Hamburg (FHH). The altitude values are given in the official height reference system of the German main altitude network as normal heights in "Meters above normal altitude zero" (NHN). The associated coordinate reference system (CRS) has been the DE_DHHN_16_NH since 01.12.2016, whose height horizon is 14-17 millimeters lower than the values of the CRS DE_DHHN_92 from 1992 valid until 30.11.2016. The FHH's high-altitude fixed-point field consists of hierarchically structured high-altitude networks from I to IV. Order. While the first three orders serve to secure the elevation reference, the IV. Order, the use height network (use heights), as the last compaction stage with around 2,600 height fixed points, the basis for all surveys with official height reference. The height fixed points are determined by the regional operations Geoinformation and Surveying via geometric levelling elements and at a demand-oriented point distance to each other. The last area-by-area check or re-determination of the altitude values took place in 2010. If necessary, individual remeasurements take place. The height is given in millimeters. Metal bolts on house facades or bridge foundations are mainly used as permanent markings. In peripheral areas with little development, for example, granite or concrete blocks introduced into the ground can also form the basis for marrowing. The markings of points in the fixed point field are survey marks within the meaning of § 7 of the HambVermG. They may only be introduced, modified, restored or removed by surveying bodies (i.e. the State Geoinformation and Surveying Company and the publicly appointed surveying engineers in Hamburg). They must not be impaired in their recognizability and usability. Anyone wishing to take measures which could jeopardise survey marks, in particular their stability, recognisability or usability, must inform the competent authority in good time. If survey marks are to be relocated, the polluter must bear the costs for this. The information on the height fixed points of the user height network can be called up free of charge by anyone as a ‘point of reference for height fixed points’ at www.geoportal-hamburg.de (search term ‘points of reference for height fixed points’). In individual cases, it may happen that height fixed points no longer exist locally or the ‘point of reference for height fixed points’ are no longer up-to-date. In these cases, feedback is requested from the named contact person. The LGV is not liable for damages resulting from the fact that the content shown, in particular height information, is not up-to-date.