Journal of Geo-information Science ›› 2016, Vol. 18 ›› Issue (8): 1030-1036.doi: 10.3724/SP.J.1047.2016.01030

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A New Image Retrieval Method Based on Image Viewshed

WU Yong1,2,*(), YAO Ling3, TONG Weimin1   

  1. 1. College of Geographical Science, Fujian Normal University, Fuzhou 350007, China
    2. Fujian Provincial Engineering Research Center for Monitoring and Assessing Terrestrial Disasters, Fuzhou 350007, China
    3. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
  • Received:2016-05-12 Revised:2016-07-01 Online:2016-08-10 Published:2016-08-10
  • Contact: WU Yong E-mail:wuyong3216@163.com

Abstract:

Image is a natural representation of the real world, which has the characteristics of intuitionistic expression and rich content. It has become an important visual data source in GIS data acquisition and application. With the rapid development of hardware terminal, the sensors integrated in mobile terminal become more abundant, and multi-sensor data fusion has become a trend in mobile GIS data collection. Aiming at the problem of obtaining azimuth deviation of mobile terminal, this paper emphasized on the acquisition algorithm of camera shooting directions, which was based on a gravity sensor and a magnetic sensor embedded in mobile terminals. Based on the EXIF format, locatable images were generated by the integrated collection of image metadata, location and direction. To overcome the disadvantages of existing modeling method of taking a surface as a point for locatable image, this paper proposed a method to build image viewshed by using image metadata, location and direction based on the model of lens’ angle of view. Multi-level grid was used to build the spatial index for the polygon feature of the image viewshed. Based on this method, a case study was conducted in Fujian province. In the experiment, 8022 locatable images were collected by field verification of remote sensing. Point based modeling and polygon based modeling were utilized to build the retrieved image set. Retrieval speed and results were compared and analyzed. It showed that the image retrieval results could be more accurate based on image viewshed modeling. It could retrieve images of which the actual shooting position located inside and outside of the retrieval area. Meanwhile, the image retrieval speed could increase 6.22 to 8.64 times by using the multi-level grid spatial index.

Key words: locatable image, exchangeable image file (EXIF) format, image viewshed, multi-level grid spatial index, image retrieval