GNSS-Assisted Integrated Sensor Orientation with Sensor Pre-Calibration for Accurate Corridor Mapping

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 m, a centimetric accuracy is reached with one GCP. With the provided sensor pre-calibration, an accuracy of 3.9 normalcnormalm is achieved without any GCP.

Simulation and Analysis of Photogrammetric UAV Image Blocks—Influence of Camera Calibration Error

“…The single-height oblique-looking flight 50-ob is, on the contrary, interesting, but is not always easy to conduct. The multi-height nadir-looking flight 3070-na is a possible alternative to 50-ob, since it introduces different flight heights and eases the correlation between parameters on the vertical axes [24]. The acquired images were then processed with MicMac, a free, open-source photogrammetric software which has been developed at IGN since 2003 [25].…”

“…The processing accuracy was evaluated by the root mean square error (RMSE) on control points (CPs) and was 1 cm. More data processing details of the presented dataset are given in Reference [24].…”

“…By comparing with 2 flights cases, the inclusion of multi-height nadir-looking flights (3070-na) has negative influence when the acquisition suffers from thermal effect. This said, the addition of multi-height nadir-looking flights still brings improvements on other aspects, for instance, it eases the correlation between camera focal length, camera height and lever-arm for mapping of flat scenes [24].…”

Detection of Levee Damage Based on UAS Data—Optical Imagery and LiDAR Point Clouds

“…Therefore, airborne data can be used in this application in order to detect the hazardous areas [5,6]. Nowadays, levee monitoring can be successfully conducted by means of remote sensing techniques, and in most cases, aerial photogrammetric data is used-especially high-resolution aerial imagery [7,8] and LiDAR (Light Detection and Ranging) point clouds [9]. LiDAR data have many advantages in comparison to photogrammetric data.…”

“…Photogrammetric flights are usually performed every few years for the same area. For corridor objects, such as levees, acquiring data using the Unmanned Aerial System (UAS) may become a more cost-efficient alternative to high-altitude photogrammetry [7,8,11]. In the literature, there are some articles available that focus on using spectral information from UAS-borne images in order to analyse and detect vegetation [12][13][14].…”