Evaluation of Classification Performance of Pole-Like Objects from MMS Images Using Convolutional Neural Network and Image Super Resolution
Department of Computer Science, College of Engineering, Nihon University
1 Nakagawara, Tokusada, Tamura-machi, Koriyama, Fukushima 963-8642, Japan
Mobile mapping systems (MMS) can capture point cloud and continuous panoramic images of roads and their surrounding environment. These data are widely used for the maintenance of road-side objects and the creation or update of road ledgers. For these purposes, there is a need to detect and classify each object from captured data, and localize them on 3D maps. Many studies have been reported on the detection and classification of pole-like objects using point clouds captured by a mounted laser scanner. Although MMS images contain valuable information related to color and shape about objects, they have not been well utilized to date for this purpose. It is reasonable to extract shape and color features from images and use them for classification. In this paper, we focus on MMS images rather than point clouds, and evaluate the classification performance for pole-like objects, such as power poles, street lamps, street-side tree, signal lights, and road signs. For classification, Convolutional Neural Network (CNN) is used, because it is known to provide better classification results than conventional methods where hand crafted features and machine learning techniques are commonly used. We also use image super resolution (ISR) techniques based on deep learning for MMS low-resolution images. In contrast to conventional methods in which entire points of pole-like objects are evaluated, our approach selects functional parts attached to the top of the pole (e.g., three-color traffic lights) for classification, because these parts represent unique characteristics of each class of object. We demonstrate the classification performance of our proposed approach through various experiments using MMS images. We also compare the difference in classification results depending on the imaging angles.
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