# ILRS Reference Point Determination Using Close Range Photogrammetry
## 3 Satellite Observing System Wettzell
### Analysis and Results  
The seven experiments of the measurement campaign given in Table 1 are individually analyzed to evaluate the influence of the different configurations onto the measurement results and to prove the repeatability of the estimates. The proprietary software package Aicon Studio 3D, which is part of the DPA measurement system, is used for preprocessing and analyzing the campaign. During a measurement experiment, the camera is connected to the software and transmits the captured images on the fly. Coded and uncoded black-and-white markers are automatically detected by pattern recognition ([16] p. 479 ff) and image coordinates are derived. Moreover, approximation values of the exterior orientation parameters, i.e., the spatial coordinates and the orientation of each camera position, are estimated. Having the approximated exterior orientation parameters and the interior orientation parameters, which are approximately known from an external camera calibration, the image coordinates are transformed by Equation (1), and approximated spatial object point coordinates are obtained. As a result of these in-process preanalyses, approximation values for all required parameters are available.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**DOY** & **Img** & **Az** & **El** & **_n_ & **Conf** \\ \hline
255 & 1336 & 6 & 7 & 478 & i \\
256 & 1793 & 6 & 7 & 485 & i \\
257 & 1659 & 6 & 6 & 431 & ii \\
258 & 1685 & 6 & 6 & 432 & ii \\
259 & 1129 & 4 & 6 & 286 & iii \\
260 & 1284 & 4 & 6 & 284 & iii \\
264 & 1799 & 6 & 7 & 588 & i \\ \hline \hline \end{tabular}
\end{table}
Table 1: Performed experiment configurations (Conf) w.r.t. to the number of telescope orientations in azimuth (Az) and elevation (El), the number of analyzable images (Img), and the effective number of marker positions \(n\). The day of year (DOY) relates to 2020.  
Figure 6: Horizontal distribution of the resulting point clouds for the three measurement configurations having: **(a)** six azimuths, seven elevations (i); **(b)** six azimuths, six elevations (ii); and (c) four azimuths, six elevations (iii). Grey ellipses depict the 1\(\sigma\) confidences derived by the fully populated dispersion of the bundle adjustment.  
Aicon Studio 3D package also provides a bundle adjustment module as described in Section 2.1. Beside the estimated parameters and the related standard deviations, parameters to evaluate the configuration and the reliability of the network are provided. However, the fully populated dispersion matrix of the estimated parameters, which is essential for a rigorous data analysis [51], is not provided [personal communication, [PERSON], 2018]. For that reason, the in-house software package JAiCov [52] was developed. The goal of the software is to readjust the final network based on the preanalysis results obtained by Aicon Studio 3D. JAiCov allows an independent verification of the adjustment results and provides the fully populated dispersion. Due to appropriate approximation values provided in a robust manner by Aicon Studio 3D, step-size control algorithms like damping, line search, or trust region approaches are currently not implemented. For numerical stabilization, the system of normal equations is preconditioned (cf. [53] p. 541 ff).