A Quick Tile Cache Generation Method Based on Dynamic Projection and Scan-Line Cropping
Abstract: Tile map cache is a kind of service cache technique for quick accessing static map. It is developed during the progress of Web GIS. In recent years, it is widely used in 3D terrain display as the funda-mental data organization method. In the progress of tile map production, original image data are usually different in data format, projection, resolution and so on because of various data sources. Meanwhile, there are other restrictions such as image cropping by area of interest because of application localization or secrecy. So the traditional map tile generation begins with image re-projection, cropping and mosaic to produce united semi-finished image, and then puts it into map tiling software. This method is inefficient and takes lots of storage. Based on the method, this article suggests a dynamic projection using linear polynomial numerical projection and image quick cropping algorithm based on scan-line filling. The experimental results show that the method can realize automatic tile generation in one-time processing. The time it used is nearly the same as traditional methods which only deal with united semi-finished image. The algorithm can finish the map tiling without generating semi-finished image. As a result, it can improve the automation and reduce the processing time.
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