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G. Navratil, E. Unger:
"Requirements of 3D cadastres for height systems";
Computers, Environment and Urban Systems, 38 (2013), March; 11 - 20.

Three-dimensional (3D) cadastral systems can only be built if there are suitable height reference systems. However, the earth is neither homogeneous nor flat, and the plumb lines are curved and not parallel. Thus, the definition of height and the implementation of geodetic height systems are complex. 3D cadastres must connect to the existing national height reference. In addition, cadastral systems are designed to persist for centuries. Over such long periods, the earth changes, from plate tectonics, erosion, human intervention, etc. Changes in the technology of measurement equipment can also occur, allowing different definitions. These considerations are important in the design of a 3D cadastre. At minimum, the height system used for the cadastre must be well-defined, to enable adjustments from potential changes in the height system or even the actual point heights.
This study examines existing height systems and the determination of height in the context of cadastral tasks. Accuracy requirements for height in a 3D cadastre are analyzed using typical examples. The selected height system must support these requirements. This study also develops the questions that must be answered and highlights the problems that can emerge in some of the solutions. There is no height reference system that fits all needs, and each solution has advantages and disadvantages. Different systems may be optimal for different countries. It may also be beneficial to allow different geometrical qualities for different parts of a country.

Three-dimensional (3D) cadastral systems can only be built if there are suitable height reference systems. However, the earth is neither homogeneous nor flat, and the plumb lines are curved and not parallel. Thus, the definition of height and the implementation of geodetic height systems are complex. 3D cadastres must connect to the existing national height reference. In addition, cadastral systems are designed to persist for centuries. Over such long periods, the earth changes, from plate tectonics, erosion, human intervention, etc. Changes in the technology of measurement equipment can also occur, allowing different definitions. These considerations are important in the design of a 3D cadastre. At minimum, the height system used for the cadastre must be well-defined, to enable adjustments from potential changes in the height system or even the actual point heights.
This study examines existing height systems and the determination of height in the context of cadastral tasks. Accuracy requirements for height in a 3D cadastre are analyzed using typical examples. The selected height system must support these requirements. This study also develops the questions that must be answered and highlights the problems that can emerge in some of the solutions. There is no height reference system that fits all needs, and each solution has advantages and disadvantages. Different systems may be optimal for different countries. It may also be beneficial to allow different geometrical qualities for different parts of a country.

Height definition, Height system, Quality requirements, Cadastre

http://dx.doi.org/10.1016/j.compenvurbsys.2012.11.002