Fast and robust geometric correction for mosaicking UAV images with narrow overlaps

Image mosaicking is essential for monitoring a wide target area using unmanned aircraft vehicle (UAV) images. An image mosaicking process requires accurate and robust geometric correction of individual images with respect to the reference plane. Tiepoint-based geometric correction methods developed so far usually assume wide overlaps between adjacent images. This article focuses on fast monitoring applications where UAVs fly very fast and image mosaics are to be generated immediately. In this case, wide overlaps might not be ensured. For this reason, we investigate a fast and robust geometric correction method for mosaicking UAV images with narrow overlaps. To ensure quickness in geometric correction, an image resampling approach using a resampling grid is presented. To ensure accuracy and robustness in geometric correction, existing transformation models are analysed in depth, and optimal models are proposed. Our proposed method shows the potential for fast monitoring applications. We also show that while existing transformation models work for images with a large overlap, perspective transformation models with full orientation parameters may suffer in images with a narrow overlap. We hope that our results can be useful when implementing an optimal solution that can simultaneously handle UAV images with different overlaps.