Research On Critical Technique Of Geo-PDF Map Cartography

Geo-PDF map is a kind of electronic map which does not only comply with PDF Reference but also provide space reference system. PDF can describe various page contents and provide strong human-computer interaction techniques. Geo-PDF map, in compliance with PDF Reference, can display hierarchically, contains functions such as annotations, bookmarks, hyperlinks, and can measure distance, area and azimuth angle. Geo-PDF map has small data quantities, which makes it especially easy to use and suitable for network transmission. On the basis of deep analysis on PDF Reference, this paper introduced the way of creating Geo-PDF maps by writing 7-bit ASCII code files or binary system code files directly, designed the cartography process of Geo-PDF maps, described the exporting method of map elements, and finally made practice on creating a Geo-PDF map as well as carried out an experimental verification on the map's browsing performance. This paper mainly studied on the following aspects:1. Built the cartography process of Geo-PDF maps. Firstly, it read map data by making use of the cartography system. Secondly, divided map data into entities and lettering annotations. Finally exported Geo-PDF maps by use of exporting modules of Geo-PDF maps.2. According to PDF Reference and requirements on cartography, this paper designed the file structure of Geo-PDF maps; implemented exporting of vector, grid Geo-PDF maps; carried out hierarchical display of vector Geo-PDF map; added various features such as labels, hyperlinks, compression, bookmarks, and extended application functions of Geo-PDF maps.3. By analyzing the device-independent coordinate system of PDF, the paper built the coordinate system of Geo-PDF maps and converted various coordinates of map symbols and lettering annotations into Geo-PDF maps correctly.4. Combining with PDF text implementation mechanism, the paper made some research and realized exporting Chinese and English map lettering, and exporting various font variants, such as Italic fonts, Shrug fonts and contour characters.5. By use of 1:4,000,000 map data from the National Fundamental Geographic Information System, this paper designed and created a vector Geo-PDF map with proportion of 1:4,000,000, a grid Geo-PDF map and a subject Geo-PDF map. It also made choices and experiment on PDF readers, tested effects of two different compression methods on the display and roaming speed of Geo-PDF maps.