Target height

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The target point height is a technical measurement term and refers to the height of a point aimed at with a theodolite or tachymeter . The point on which the measuring device stands is called the instrument position , the points that are recorded from there are target points. This distinction is important for evaluating the measurement data from a survey. In today's measuring devices with automatic data flow , the target points are defined using code.

Occasionally the term target height is used only for the reflector or signal height on the measuring stick .

Admission procedure

Any number of target points can be measured from one point of view. A modern instrument ( total station , digital leveling device) records these points as raw data in an internal coordinate system, the zero point of which lies at the intersection of the vertical standing axis and the horizontal tilting axis of the device. In order to calculate the target point height, i.e. the Z coordinate of the point, the vertical distance between the tilt axis of the device and the marked ground point (tilt axis or instrument height ) and the vertical signal height (reflector height) at the target point must also be noted or saved once for each target point to perform the following calculation:

H ZP = Target point height
H SP = Position height
H KA = Tilt axis height
H = Difference in altitude
H S = Signal height

The position coordinates ( X and Y coordinates ), height (Z coordinate) and directional orientation of the point of view do not have to be known during the measurement; they can also be calculated afterwards if target points or fixed points are also included in the measurement, whose coordinates (X / Y / Z) are known. The internal coordinates are converted into the reference coordinate system by transformation . The transformation constants thus apply to all target points that were measured from one point of view.

evaluation

After the target point coordinates have been calculated, it is no longer necessary to differentiate between stations and target points in the total station. It only serves to create data groups during the evaluation that are assigned to the current transformation constants of a point of view. In the case of sequential storage of the data, however, only the viewpoints need to be identified explicitly. Target points are all subsequent data records up to the next station entry or the end of the file at the last station. After the evaluation of the measurement data, all points are equivalent in terms of point data management, as they are available in a uniform reference system.

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