Adjustment of 3D Net (ACN)
Prior to the complete spacial adjustment, both the level and the planimetric nets must be preprocessed and optionally adjusted. The 3D adjustment is comprised of both total station and electronic level measurements. The following observation types are picked in chronological order.
Slope distances
Included if both the horizontal distance and elevation difference were measured from total stations. If the horizontal distance was measured from a total station, but the elevation difference was measured using only a level, they are included as separate measurements.
Preprocessor
Observed slope distances are computed as
then, to find their TSDs, the partial derivatives of the function are computed:
Partial derivatives
Adjustment
The slope distance function is defined to return the distance in space between points and
Model matrix elements
Zenith angles
Similarly to the slope distances, included only if both planimetric and altimetric quantities were measured from total stations.
Preprocessor
Partial derivatives
Adjustment
The zenith angle function is defined to return the zenith angle between points and
Model matrix elements
NOTE
This implementation of the complete 3D adjustment is partially flawed, due to the fact that it does not account for cases where only a zenith angle or slope distance may have been measured between an instrument and a prism, which excludes valuable information from the adjustment.
Level lines
Typically only constructed from electronic level measurements, though in case TS measurements are included only in the 1D net, they might be averaged alongside them.
Preprocessor
The preprocessor averages all electronic level measurements according to their TSDs and includes any TS measured elevation differences, for whose points zenith angles were not computed.
Adjustment
Model matrix elements
Horizontal distances
Included unless a slope distance has been included between the points.
Preprocessor
The preprocessor uses data from PSD.
Adjustment
Model matrix elements
Horizontal angles
Added from each station according to its measured angular directions. If a station has measured directions, angles will be included, going in clockwise direction.
Preprocessor
The preprocessor uses data from PSD.
Adjustment
Model matrix elements
Control point coordinates
Optionally included in module options. Useful if the accuracy of the measurements is considered higher than that of the control points since it allows them to be moved slightly to fit the network better. Enabling this option is encouraged even for adjustments containing high class control points.