Study On The Methods To Represent Spatial Distribution Of Spatial Point Group Data

As indispensable means of expression to present the objective world and to convey the spatial information, map occupies an important position both in scientific research and people’s daily life. In the thematic maps, punctate distribution is one of the most common spatial distributions of thematic elements. Individual surface features that actually exist like schools and hospitals, and abstract things with spatial distributions, such as population and observed meteorological data, are all typically recorded and stored in the form of points. Along with the development of satellite positioning technology and mobile internet, it is increasingly convenient to obtain spatial point group data, which result in the application breadth of massive point group data being larger than ever before. Through the intuitive and effective visualization of point data, thematic information can be shown comprehensively and diversely, reflecting its distribution density, regional differences, dynamic changes and other features. This paper analyzed the limitation of traditional methods in the aspects like cartography form and visual perception, and explored how to express thematic information quickly, intuitively and comprehensively using the massive point group data.The paper reviewed the traditional point group data representation methods, and then innovated on this basis. Basic physics illumination models, such as lighting model and diffusion model, are introduced into the mapping process, to research the mapping principles and application features of night view map and cartogram. The 3D mapping methods of point group data were investigated in three respects:3D surface map, dynamic histogram map, and columnar grid map. The application characteristics of these new methods of thematic maps are demonstrated by using thematic data like KTV outlets, bars, population and GDP in each region.In this paper, the main work and research results are as follows:(1) We first reviewed the common representation methods for point group data, and then analyzed their characteristics of expression and applicable data. Using the data of KTV outlets in Mainland China, the paper discussed the application of point value method, the amount of substrate method, and spatial interpolation methods in density mapping.(2) Starting from the electronic map color scheme, the paper introduced light attenuation model of point source to simulate lighting effects in electronic map, and produced night view maps of KTV outlets in Mainland China and Jiangsu Province. The study suggests that night view map can be understood as a combination of point value method and the nuclear density mapping, which could not only reflect the aggregation characteristics of points group in the entire region, but also retain the individual spatial information of each discrete point.(3) This paper analyzed and realized the diffusion-based method for producing density-equalizing maps, then produced "Cartogram of China’s 2012 population distribution" and "Comparison of GDP increase in Mainland China (2002-2012)". The mapping examples show that cartogram have good results in terms of reflecting spatial distributions and dynamic changes of thematic data.(4) The data of KTV outlets in Mainland China, GDP in each region of Mainland China in 2002-2012, and the KTV outlets and bars in the main city of Nanjing were used to discuss the application characteristics of 3D surface map, dynamic histogram map, and columnar grid map. The 3D expressions of thematic information could improve the maps’visual effects, transmit spatial information of more dimensions, and decrease the dependence of thematic maps on colors.In conclusion, this paper studied the characteristics and applications of night view map, cartogram, and several 3D maps, and illustrated by mapping examples. These methods could not only be applied to point group data’s cartographic representation, but also be used by other types of thematic data. This paper would provide references for cartographies in related science researches and life applications, showing certain significance.