An investigation into the integration of oblique photogrammetry into UAV based SfM surveys for the production of highly accurate models of near-vertical, vertical or sub-vertical surfaces.

This research aims to investigate the integration of oblique images into unmanned aerial vehicle (UAV) based Structure from Motion (SfM) surveys. With the recent proliferation of UAVs and the development of SfM photogrammetry, significant potential exists to advance our ability in capturing the 3D environment around us. Surveys can now be conducted at a much higher resolution, both spatial and temporal, providing the opportunity to see far more than the traditional platforms have allowed. Limitations, however, still exist and the continued reliance on vertical oriented surveys to capture increasingly complex 3D environments is not ideal. Oblique photogrammetry by contrast, offers significant potential to capture data from near-vertical and vertical surfaces, previously missed by nadir surveys. This study considers the integration of oblique images into UAV aerial surveys for the purpose of improving the capture of complex topography. A systematic approach is taken, whereby variables such as the oblique angle and horizontal offset are considered in isolation, along with underlying SfM repeatability. Significant improvements in the pickup of near-vertical surfaces have been shown to be possible, with only minor adjustments to the oblique angle. Furthermore, oblique surveys report points clouds with both increased density and completeness, along with an ability to model smaller-scale structure than the equivalent vertical surveys