This study investigates the optimal distribution and pattern of ground control points (GCPs) in aerial photogrammetric projects. Aerial triangulation (AT), also known as bundle adjustment, is the ...fundamental step in refining 3D reconstruction models and camera positions, thereby minimizing reprojection errors. The study utilizes data from a national project in Romania, employing high-resolution aerial images acquisition using photogrammetric sensors. The project has rigorous requirements of ground control points (GCP) placement and field measurements using GNSS and geometric leveling techniques. The study employs various scenarios, manipulating the number and distribution of GCPs, to assess their influence on planimetric and altimetric accuracy. Results indicate that the configuration and number of GCPs significantly affect the accuracy of photogrammetric products, such as dense image point clouds, digital surface models, and orthophotos. Moreover, the study underscores the importance of precise GCP determination methods, especially in regions lacking a precise gravimetric geoid model. In scenarios with inadequate GCP coverage the outcomes have inferior quality, emphasizing the critical role of GCPs in ensuring the quality of photogrammetric products. Overall, the research gives a clear view on the best placement patterns of GCPs and their influence on AT process evaluation performed in check points (CHKs).
The project of modelling a quasigeoid for the area of Romania will run in stages, based on the relative gravimetric measurements made on the area of every county, in gravimetric points from the 1st ...and 2nd order gravimetric network, GNSS and precision leveling measured checkpoints and also new designed points (determined with GNSS/RTK). “Remove-restore” algorithm will be used for compiling the geo-gravimetric quasigeoid, used prior in the pilot project of modelling a quasigeoid for Bucharest area and also the method of collocation/minimum curvature for generating the anomalies grid.In this article are presented the main activities that took place in 2016 for creating the pilot projects in three counties of Romania and the results obtained till now as well as the perspective for the next years.
