Automated Georectification and Mosaicking of UAV-Based Hyperspectral Imagery from Push-Broom Sensors
byY. Angel, D. Turner, S. Parkes, Y. Malbéteau, A. Lucieer, M.F. McCabe
Year:2020DOI:10.3390/rs12010034
Extra Information
Remote Sensing, Vol 12, Issue 1, p. 34, (2020)
Abstract
Hyperspectral systems integrated on
unmanned aerial vehicles (UAV) provide unique opportunities to conduct
high-resolution multitemporal spectral analysis for diverse
applications. However, additional time-consuming rectification efforts
in postprocessing are routinely required, since geometric distortions
can be introduced due to UAV movements during flight, even if
navigation/motion sensors are used to track the position of each scan.
Part of the challenge in obtaining high-quality imagery relates to the
lack of a fast processing workflow that can retrieve geometrically
accurate mosaics while optimizing the ground data collection efforts. To
address this problem, we explored a computationally robust automated
georectification and mosaicking methodology. It operates effectively in a
parallel computing environment and evaluates results against a number
of high-spatial-resolution datasets (mm to cm resolution) collected
using a push-broom sensor and an associated RGB frame-based camera. The
methodology estimates the luminance of the hyperspectral swaths and
coregisters these against a luminance RGB-based orthophoto. The
procedure includes an improved coregistration strategy by integrating
the Speeded-Up Robust Features (SURF) algorithm, with the Maximum
Likelihood Estimator Sample Consensus (MLESAC) approach. SURF identifies
common features between each swath and the RGB-orthomosaic, while
MLESAC fits the best geometric transformation model to the retrieved
matches. Individual scanlines are then geometrically transformed and
merged into a single spatially continuous mosaic reaching high
positional accuracies only with a few number of ground control points
(GCPs). The capacity of the workflow to achieve high spatial accuracy
was demonstrated by examining statistical metrics such as RMSE, MAE, and
the relative positional accuracy at 95% confidence level. Comparison
against a user-generated georectification demonstrates that the
automated approach speeds up the coregistration process by 85%.