Advances in Earth Science ›› 2010, Vol. 25 ›› Issue (3): 373-283. doi: 10.11867/j.issn.1001-8166.2010.03.0373

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Computating Changjiang's Spherical Center of Gravity and Analysis of Scaling Effects

Song Dunjiang,Zhao Zuoquan   

  1. Institute of Policy and Management, Chinese Academy of Sciences, Beijing  100190, China 
  • Received:2009-08-28 Revised:2010-12-27 Online:2010-03-10 Published:2010-03-10

Song Dunjiang,Zhao Zuoquan. Computating Changjiang's Spherical Center of Gravity and Analysis of Scaling Effects[J]. Advances in Earth Science, 2010, 25(3): 373-283.

Changjiang River is a characteristic feature of China. The length of Changjiang River is about 6211.3 kilometers, the longest river in China, and the third longest river in the world. As a spatially distributed geographical feature, Changjiang not only has nonspatial attributes, such as length, but also many spatial attributes, for example, the center of gravity (or centroid), range, intensity, orientation, and shape in space. To study the spatial distribution of Changjiang River, this paper proposes a method for spatial statistics of spherical line features. To get rid of the effects of spherical curvature, a model of three dimension vector of spherical coordinates is used. To study the intrinsic scaling effects of spatial data, spatial partitioning of three different cell size(1 000 m,100 m and 10m) is proposed for the spatial statistics of Changjiang. To study the uncertainty of computational results, a simple spatial sampling method is applied. For simplicity, this paper takes the spherical center of gravity of Changjiang as an example. By ten times' 3% random sampling, the paper has also given the probability error of the center of gravity of Changjiang River. From the 10m spatial partitioning of Changjiang, the center of gravity of Changjiang results as N(30°25′37″),E(104°52′00″), based on which we get the spatial density 2D curve of Changjiang. The max spatial distribution percent every 100 kilometers away from the center of Changjiang is 22.2%, about 500~600 km. From 10 ten times spatial sampling, it can be concluded that, when 10 m spatial partitioning is applied, the error of spherical center is probably 50% less than 10 km, and 100% less than 17 km; when 100 m spatial partitioning is applied, the error of spherical center is probably 50% less than 20 km, and 100% less than 40 km; when 1 km spatial partitioning is applied, the error of spherical center is probably 50% less than 60 km, and 100% less than 100 km.Sphere-based spatial analysis is a global trend in GIS, this threedimensionalvector based spatial statistics method for spherical center of gravity also applicable to the areal features. Changjiang region is densely populated and so the study of Changjiang′s spatial distribution is very important. This paper can add up to people′s knowledge of Changjiang, which is also useful for the studies of economy, policy making related to the Changjiang, for the important geographical information or background information of Changjiang provided in this paper. The spatial data of Changjiang is from Data Center for Resources and Environmental Sciences of the Chinese Academy of Sciences (RESDC). Changjiang is extracted manually from the hydraulic network data.

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