Abstract
Feature extraction and matching is a crucial task in the fields of computer vision and photogrammetry. Even though wide researches have been reported, some issues are still existing for oblique images. This paper exploits the use of on-board GNSS/IMU (Global Navigation Satellite System/Inertial Measurement Unit) data to achieve efficient and reliable feature extraction and matching for oblique unmanned aerial vehicle (UAV) images. Firstly, rough POS (Positioning and Orientation System) is calculated for each image with cooperation of on-board GNSS/IMU data and camera installation angles, which enables image rectification and footprint calculation. Secondly, two robust strategies, including the geometric rectification and tile strategy, are considered to address the issues caused by perspective deformations and to relieve the side-effects of image down-sampling. According to the results of individual performance evaluation, four combinations of these two strategies are designed and comprehensively compared in BA (Bundle Adjustment) experiments by using a real oblique UAV dataset. The results reported in this paper demonstrate that the solution with the tiling strategy is superior to the other solutions in terms of efficiency, completeness and accuracy. For feature extraction and matching of oblique UAV images, it is proposed to combine the tiling strategy with existing workflows to achieve an efficient and reliable solution.
Highlights
In recent years, unmanned aerial vehicle (UAV) has emerged as an attractive data acquisition platform for a wide range of photogrammetry and remote sensing tasks [1,2]
The GNSS/IMU data is firstly transformed from the navigation system to a local tangent plane (LTP) coordinate system used in this study, which is used for rough positioning and orientation (POS) calculation
We would evaluate the performance of two potential solutions, including the global geometric rectification and tiling strategy, for feature extraction and matching of oblique
Summary
UAV has emerged as an attractive data acquisition platform for a wide range of photogrammetry and remote sensing tasks [1,2]. Compared with the conventional aerial- or satellite-based platforms, an UAV platform features rapid data acquisition, efficient cost and easiness of use. Even with a non-metric camera integrated, an UAV-based photogrammetric system could efficiently capture images with extremely high spatial resolution because of relative lower flight heights. Oblique imaging is another commonly adopted technique aiming at data acquisition from side-looking directions. It records both footprints and facades of targets, especially for buildings in urban environment when compared with the traditional vertical imaging systems
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