2 research outputs found
Integration of LiDAR and photogrammetric data for enhanced aerial triangulation and camera calibration
PhD ThesisThe integration of complementary airborne light detection and ranging (LiDAR) and
photogrammetric data continues to receive attention from the relevant research
communities. Such an approach requires the optimized registration of the two data types
within a common coordinate reference frame and thus enables the cross-calibration of
one information source against another. This research assumes airborne LiDAR as a
reference dataset against which in-flight camera system calibration and validation can
be performed. The novel methodology involves the production of dense
photogrammetric point clouds derived using the simultaneous adjustment of
GNSS/IMU data and a dense set of photogrammetric tie points. Quality of the generated
photogrammetric dataset is further improved through introducing the self-calibration
additional parameters in the combined adjustment. A robust least squares surface
matching algorithm is then used to minimise the Euclidean distances between the two
datasets. After successful matching, well distributed LiDAR-derived control points
(LCPs) are automatically identified and extracted. Adjustment of the photogrammetric
data is then repeated using extracted LCPs in a self-calibrating bundle adjustment. The
research methodology was tested using two datasets acquired using different
photogrammetric digital sensor systems, a Microsoft UltraCamX large format camera
and an Applanix DSS322 medium format camera. Systematic sensitivity testing
included the influence of the number and weighting of LCPs required to achieve
optimised adjustment. For the UltraCamX block it was found that when the number of
control points exceeded 80, the accuracy of the adjustment stabilized at c. 2 cm in all
axes, regardless of point weighting. Results were also compared with those from
reference calibration using surveyed ground control points in the test area, with good
agreement found between the two. Similar results were obtained for the DSS322 block,
with block accuracy stabilizing at 100 LCPs. Moreover, for the DSS322 camera,
introducing self-calibration greatly improved the accuracy of aerial triangulation