  This report summarizes the results of Learning to Understand Aerial Images
(LUAI) 2021 challenge held on ICCV 2021, which focuses on object detection and
semantic segmentation in aerial images. Using DOTA-v2.0 and GID-15 datasets,
this challenge proposes three tasks for oriented object detection, horizontal
object detection, and semantic segmentation of common categories in aerial
images. This challenge received a total of 146 registrations on the three
tasks. Through the challenge, we hope to draw attention from a wide range of
communities and call for more efforts on the problems of learning to understand
aerial images.
