Abstract
With the development of unmanned aerial vehicles (UAVs) and global navigation satellite system (GNSS), the accurate camera positions at exposure can be known and the GNSS-assisted bundle block adjustment (BBA) approach is possible for integrated sensor orientation (ISO). This study employed ISO approach for camera pose determination with the objective of investigating the impact of a good sensor pre-calibration on a poor acquisition geometry. Within the presented works, several flights were conducted on a dike by a small UAV embedded with a metric camera and a GNSS receiver. The multi-lever-arm estimation within the BBA procedure makes it possible to merge image blocks of different configurations such as nadir and oblique images without physical constraints on camera and GNSS antenna positions. The merged image block achieves a better accuracy and the sensor self-calibrated well. The issued sensor calibration is then applied to a less preferable acquisition configuration and the accuracy is significantly improved. For a corridor acquisition scene of about 600 , a centimetric accuracy is reached with one GCP. With the provided sensor pre-calibration, an accuracy of 3.9 is achieved without any GCP.
Highlights
For traditional airborne photogrammetry with unmanned aerial vehicles (UAVs), camera poses are determined indirectly using the well-known method bundle block adjustment (BBA)
The accuracy was evaluated with check points (CP) and the root-mean-square (RMS) of residuals on CPs was used as the accuracy criteria
The photogrammetric accuracy and estimation results were given in two cases: without ground control points (GCPs) and with one GCP used in the BBA procedure
Summary
For traditional airborne photogrammetry with unmanned aerial vehicles (UAVs), camera poses (position and attitude) are determined indirectly using the well-known method bundle block adjustment (BBA). The photogrmmetric accuracy is strongly dependent on the acquisition geometry and the number of ground control points (GCPs) as well as their distribution within the image block [1,2]. Among different configurations of UAV acquisitions, the corridor mapping is of particular interest, for instance in dike surveillance, highway planning and power line surveys [3]. While the employment of a large number of GCPs prevents stereo model distortion [4], the field work of GCP establishment can be substantially expensive and time-consuming
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