On Properties of Automatically Measured Tie Point Observations

In this article results of an investigation concerning usage of automatically measured tie point observations in aerial triangulation are given. Especially the effect of amount and accuracy of tie point observations on the block quality has been concerned. Simulation and empirical techniques have been used. Simulation study proved that increase in the amount of tie points improve the quality of aerial triangulation, provided that correct functional and stochastic models are used in the block adjustment. The quality improvement was especially seen as increasing accuracy of orientation parameters and decreasing sensitivity of orientation parameters on the tie point measurement errors. Based on simulation, suggestion for sufficient amount of tie points in typical conventional photogrammetric cases was derived. Empirical investigation showed that when using large amount of automatically measured tie points a high accuracy can be achieved. However, results of the empirical test blocks gave an indication that proper handling of systematic image deformations and the stochastic model of adjustment may get more importance when more observations are used.