PANet Paper Walkthrough: When Feature Pyramids Go Bottom-Up

Path Aggregation Network (PANet) improves upon the Feature Pyramid Network (FPN) by addressing the flow of spatial information in object detection models. While FPN enriches shallow layers with high-level semantic information, it fails to provide deep layers with low-level spatial information, which degrades due to the long path through the network backbone. PANet introduces an additional bottom-up path augmentation that creates a shorter pathway for spatial details from early layers to reach the deepest feature maps. This bidirectional information flow enhances both semantic and spatial information at all levels, improving detection accuracy for objects of all sizes.