一种用于景象匹配导航的新型图像配准算法

Novel image registration algorithm for scene-matching navigation

  • 摘要: 高精度定位与导航技术是实现无人机自主飞行的核心要素之一,当在卫星拒止条件下,卫星导航无法进行准确定位时,景象匹配视觉导航技术因其设备结构的简洁性和被动式定位的高精度而备受关注,当它与惯性系统结合时,能够构建出一个高度自主且精确的导航系统. 在景象匹配系统中,最为关键的步骤是将实时拍摄到的图像与预先装载的基准图进行精确配准. 然而,这一过程面临着无人机高速飞行和基准图多源性的双重挑战,这要求图像配准在确保精度的同时,还必须具备快速响应和强鲁棒性. 为了克服这些难题,本文提出了一种名为Dimensionality reduction second-order oriented gradient histogram(DSOG)的描述子,该描述子通过描述图像定向梯度信息的像素特征,有效地实现了图像特征的提取. DSOG描述子采用区域特征的特征提取策略,实现对不同传感器采集到的图像数据进行精准匹配,满足飞行器在全天候的条件下实现高精度导航的需求. 在此基础上,还设计了一种优化后的相似度度量匹配模板,该模板在频域上对传统的基于快速傅里叶变换的特征表示快速相似度度量算法进行了优化,减少了匹配过程中的冗余计算. 本文提出的匹配框架经过对不同类型多模态图像的广泛评估,实验数据包括可见光-可见光、可见光-合成孔径雷达、可见光-高光谱等异源图像对,同时,将提出的算法于目前主流的图像配准算法进行了对比,结果显示,与当前主流方法相比,在保持匹配精度的前提下,显著提升了计算效率,同时相比于深度学习算法,本文提出的算法无需经过大量的数据训练即可得到实际使用所需的泛化性. 具体来说,本文提出的算法在多模态图像的平均匹配时间仅为1.015 s,不仅满足了无人机景象匹配导航对实时性和鲁棒性的要求,而且为无人机的广泛应用提供了强有力的技术支持.

     

    Abstract: High-precision positioning and navigation technology are crucial for the autonomous operation of unmanned aerial vehicles (UAVs), enabling them to determine their location and navigate to predetermined destinations without human intervention. In scenarios where satellite navigation is unavailable, image matching–based visual navigation technology becomes essential owing to its simple device structure and high accuracy in passive positioning. When combined with inertial systems, this technology creates a highly autonomous and precise navigation system. Compared with traditional simultaneous localization and mapping for visual navigation, which requires extensive computation for continuous point cloud mapping, scene matching ensures real-time performance without such demands. At the core of the image-matching system is the registration of real-time captured images with preloaded reference images, a task complicated by the high-speed flight of UAVs and diverse image sources. This necessitates a rapid and robust registration process while maintaining high precision. To tackle these challenges head-on, we developed a novel descriptor known as dimensionality reduction second-order oriented gradient histogram (DSOG), which is characterized by its high precision and robustness, making it ideal for image matching. It effectively extracts image features by delineating pixel characteristics of oriented gradients and uses a regional feature extraction strategy. This is advantageous over point and line features, especially when handling nonlinear intensity differences among heterogeneous images during matching, enabling precise matching of image data collected by different sensors and satisfying high-precision navigation needs under all-weather conditions for aerial vehicles. Building upon this descriptor, we have crafted an optimized similarity measurement matching template. This enhances the traditional fast similarity measurement algorithm, which uses fast Fourier transform in the frequency domain, thereby reducing computational redundancy inherent in the matching process. Our framework has been rigorously evaluated across diverse multimodal image pairs, including optical–optical, optical–SAR, and optical–hyperspectral datasets. Our algorithm has been compared with current state-of-the-art image registration methods, including traditional feature–based approaches such as DSOG, histogram of oriented phase congruency (HOPC), and radiation-variation insensitive feature transform (RIFT), as well as deep learning–based techniques such as Loftr and Superpoint. The results demonstrate that our method considerably improves computational efficiency while maintaining matching precision. Moreover, unlike deep learning algorithms that require extensive data training for generalization, our algorithm achieves the necessary level of generalization without such extensive training. In particular, our algorithm achieves an average matching time of only 1.015 s for multimodal images, meeting real-time performance and robustness requirements for UAV scene–matching navigation. Our study not only offers innovative solutions for enhancing the precision and reliability of UAV navigation systems but also carries substantial practical significance. It has broad application potential in military, civil, and commercial sectors, thereby shaping the future of autonomous navigation in the aerospace industry.

     

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