Rotation augmentations generally improve a model's invariance/equivariance to rotation - except in object detection. In object detection the shape is not known, therefore rotation creates a label ambiguity. We show that the de-facto method for bounding box label rotation, the Largest Box Method, creates very large labels, leading to poor performance and in many cases worse performance than using no rotation at all. We propose a new method of rotation augmentation that can be implemented in a few lines of code. First, we create a differentiable approximation of label accuracy and show that axis-aligning the bounding box around an ellipse is optimal. We then introduce Rotation Uncertainty (RU) Loss, allowing the model to adapt to the uncertainty of the labels. On five different datasets (including COCO, PascalVOC, and Transparent Object Bin Picking), this approach improves the rotational invariance of both one-stage and two-stage architectures when measured with AP, AP50, and AP75. The code is available at \url{https://github.com/akasha-imaging/ICCV2021}.

本文探讨了原先在物体检测中使用的最大框方法会导致误差较大，提出了一种新的椭圆形框方法来增强模型对旋转的不变性。同时，引入旋转不确定性损失，使模型能够适应标签的不确定性，并通过实验验证了该方法在几个不同的数据集上能够显著提高模型的旋转不变性。

目标检测中的旋转不变性