A Solid angle based coordinate system for global GIS
Koji Kajiwara
Institute of Industrial Science, University of Tokyo
7-22-1, Roppongi, Minato-ku, Tokyo, 106
Japan
Abstract An equal-area projected raster image format for the global database, which can be the main source of Global Geographic Information System (GGIS), was discussed. Equal solid angle projection method, which is similar to the sinusoidal projection, is proposed to construct a global data in raster image format. In this paper, a way of constructing the image and the result of estimation of area error are described.
1. Introduction
For the Earth surface monitoring, construction of Global Geographic Information System (GGIS) which includes global database has been required. The database should include many sort of data such as terrain model, land and sea surface temperature, precipitation, various kind of indices like vegetation index, satellite data and etc. Currently, some raster type global data which can be source of global database are existed, and most of them select plate carree (longitude/latitude) projection. The plate carree projected data can be treated easily as simple digital imagery which described in column and row. When we use the data, it is enough to simply copy each pixel from outer storage devices into 2 dimensional array of computer memory. In the projection, however, pixels in mid or high latitude region have a large area distortion, in other words, plate carree projected data are variable area scale data. Considering the use of the data in GGIS, any data format includes a large area distortion can not be considered as a suitable database for global level analysis.
In this paper, equal solid angle projection for global data which is similar to sinusoidal projection was proposed. In section 2, basic concept of this projection method is described. In following section, results of area error estimation on several resolutions are shown. Finally, in the section 4, advantages and disadvantages of this projection are discussed.
