# ORSIm Detector: A Novel Object Detection Framework in Optical Remote Sensing Imagery Using Spatial-Frequency Channel Features

## TL;DR

This paper introduces ORSIm detector, a new object detection framework for optical remote sensing images that combines spatial and frequency domain features to improve robustness against scale and rotation variations.

## Contribution

The paper proposes a novel spatial-frequency channel feature (SFCF) and an integrated detection framework that enhances feature representation and detection speed in remote sensing imagery.

## Key findings

- Outperforms previous state-of-the-art methods on airborne datasets
- Effectively handles object scale and rotation variations
- Achieves faster detection through mathematical scaling estimation

## Abstract

With the rapid development of spaceborne imaging techniques, object detection in optical remote sensing imagery has drawn much attention in recent decades. While many advanced works have been developed with powerful learning algorithms, the incomplete feature representation still cannot meet the demand for effectively and efficiently handling image deformations, particularly objective scaling and rotation. To this end, we propose a novel object detection framework, called optical remote sensing imagery detector (ORSIm detector), integrating diverse channel features extraction, feature learning, fast image pyramid matching, and boosting strategy. ORSIm detector adopts a novel spatial-frequency channel feature (SFCF) by jointly considering the rotation-invariant channel features constructed in frequency domain and the original spatial channel features (e.g., color channel, gradient magnitude). Subsequently, we refine SFCF using learning-based strategy in order to obtain the high-level or semantically meaningful features. In the test phase, we achieve a fast and coarsely-scaled channel computation by mathematically estimating a scaling factor in the image domain. Extensive experimental results conducted on the two different airborne datasets are performed to demonstrate the superiority and effectiveness in comparison with previous state-of-the-art methods.