Comparison of SpatialAnalyzer and Different Adjustment Programs

Net adjustment is one of the basic tools for various surveying tasks. Among transformation of coordinates or the analysis and comparison of geometries, the adjustment of geodetic networks is an important part of the surveyor's work. The market offers a number of software solutions, both commercial and freeware.

All the programs have the ability to process terrestrial observations (distance, zenith angle, horizontal direction) in common. Apart from that, the programs differ in various aspects, which are important for the customer's choice. For instance, the net dimensions are not the same with each piece of software. Some programs do not offer a proper 3D adjustment. They handle horizontal position and height separately and therefore ignore the mathematical dependencies between the two components.

Seeing the range of software solutions, the question arises, whether the programs give equivalent results. Earlier evaluations of net adjustment programs, including New River Kinematics' SpatialAnalyzer (SA), revealed on the one hand almost identical adjustment results for the classic programs. On the other hand, the evaluations showed that SA, using a different mathematical model (bundle adjustment) yields clearly distinguishable deviations. ... mehrHence, in this paper the authors focused on SA with the classic programs as reference. The first part of the comparison deals with the results of evaluating a terrestrial network. Due to the fact that the programs do not account for the earth's curvature in a standardized way, the network is of small size to overcome the need of pre-processing.

The second part of the paper compares the results of the evaluation of basic geometries (plane, circle, cylinder, sphere) using SA and other software packages with the least squares solution obtained in a rigorous Gauss Helmert model.