SAANet: Spatial adaptive alignment network for object detection in automatic driving Abstract   Both images and point clouds are beneficial for object detection in a visual navigation module for autonomous driving. The spatial relationships between different objects at different times in a bimodal space can vary significantly. It is difficult to combine bimodal descriptions into a unified model to effectively detect objects in an efficient amount of time. In addition, conventional voxelization methods resolve point clouds into voxels at a global level, and often overlook local attributes of the voxels. To address these problems, we propose a novel fusionbased deep framework named SAANet. SAANet utilizes a spatial adaptive alignment (SAA) module to align point cloud features and image features, by automatically discovering the complementary information between point clouds and images. Specifically, we transform the point clouds into 3D voxels, and introduce local orientation encoding to represent the point clouds. Then, we use a sparse convolutional neural network to learn a point cloud feature. Simultaneously, a ResNetlike 2D convolutional neural network is used to extract an image feature. Next, the point cloud feature and image feature are fused by our SAA block to derive a comprehensive feature. Then, the labels and 3D boxes for objects are learned using a multitask learning network. Finally, an experimental evaluation on the KITTI benchmark demonstrates the advantages of our method in terms of average precision and inference time, as compared to previous stateoftheart results for 3D object detection.

A Geometric Convolutional Neural Network for 3D Object Detection We propose a method for accurate 3D vehicle detection based on geometric deep neural networks. From only a single RGB image, the framework is able to recover the 3D positions and predict 3D bounding boxes. In particular, the algorithm leverages single image depth estimation and semantic segmentation to produce 3D point cloud for specific objects. By geometrically constraining the object dimensions, an accurate and stable 3D bounding box which tightly fits into the real object can be estimated. We verify the effectiveness and robustness of our method by comparing with other recent stateofart methods on the challenging KITTI 3D benchmark dataset as well as synthetic Virtual KITTI dataset. Without requiring ground truth 3D labels, our method is able to produce competitive and robust performance in 3D scene understanding and detection.