This study evaluates seven prominent SIFT implementations for feature detection in Wide Area Motion Imagery (WAMI): Lowe's archived code, VLFeat, OpenCV, SIFT anatomy, CudaSIFT, SiftGPU, and PopSift. We use spatio-temporal patch animations, termed ThumbTracks, to assess each method's performance in terms of jitter, wandering, and track switches. Additionally, we analyze the clustering of SIFT descriptors using t-distributed stochastic neighbor embeddings. Our results reveal significant variations in the performance of different SIFT variants, with implications for their suitability in various WAMI applications. We provide recommendations for selecting the most appropriate SIFT implementation based on feature stability, computational efficiency, and accuracy requirements.
Shadows in aerial images can hinder the performance of various vision tasks, including object detection and tracking. Shadow detection networks see a reduction in performance in mid-altitude wide area motion imagery (WAMI) data since they lack the related data for training. Aerial WAMI data collection is a challenging task, and the variety of weather conditions that can be captured is limited. Moreover, obtaining accurate ground truth shadow masks for these images is difficult, where manual methods are infeasible and automatic techniques suffer from inaccuracies. We are leveraging the advanced rendering capabilities of Unreal Engine to produce city-scale synthetic aerial images. Unreal Engine can provide precise ground-truth shadow masks and cover diverse weather and lighting conditions. We further train and evaluate an existing shadow detection network with our synthetic data to improve the performance on real WAMI datasets.
We explore an approach for vision-based GPS denied navigation of drones. We find SuperPoint/Superglue feature correspondences between two coplanar images: the drone image on the ground, and a satellite view of the flight area. The drone image is projected onto the ground using non-GPS data available to the drone, namely the compass and the barometer. Features on the drone image are projected back to the drone camera plane. Features on the satellite image are projected into 3D using a digital elevation map. The correspondences are then used to estimate the drone’s position. Drone coordinate estimates are evaluated against drone GPS metadata.
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