Case studies are provided in the last 2 chapters of this book. In addition to the theoretical examination of the topic, this book includes detailed practical content helpful to those charged with implementation of tile-based systems. Attention is devoted to understanding and development of algorithms needed to make tile-based systems functional and efficient. Topics include discussions of projections, coordinate systems, image processing, data basing and indexing requirements and web access. Tile-Based Geospatial Information Systems: Principles and Practices presents a detailed examination of the principles of tile-based systems. They have been followed by the traditional GIS community, government organizations and open source development communities, because tile based systems yield faster and work stronger with 3-D mapping tools. The trend towards tile-base systems was started by Internet services companies, such as Google, Yahoo, and Microsoft. Tile-based online mapping systems have replaced traditional Web GIS systems, because of their improved speed and usability. In addition, the caching mechanism based on vector tiles can substantially reduce the response time and network throughput under the wireless multihop scenarios. The result shows that the GeoTile system can serve vector tiles for users conveniently and friendly. We implement the GeoTile prototype system and conduct comprehensive real-world experiments to evaluate the performance. Since GeoTile enables all network nodes to cache and process geospatial data tiles, requests may be handled before they actually reach the server. In GeoTile, a tile request from the mobile client relies on multihop communication over intermediate nodes to reach the server. To address this issue, we designed a scheme based on vector tiles to organize spatial data and proposed a system named GeoTile for geospatial data caching and sharing. Despite the potential overlap among nearby users’ geospatial data demands, it has not been feasible to share geospatial data with peer wireless devices directly. Mobile applications based on geospatial data are nowadays extensively used to support people’s daily activities. The combination of tile mapping and opacity control provides a new way of enabling user interaction with online maps and provides a valuable new tool for the modern cartographer. Benefits include, image comparison, map merging, and masking effects. By providing an interactive tool to control level of opacity on tiles, the cartographer can effectively combine two views. A significant disadvantage of tiled overlays is that they totally obscure the underlying base map. By enabling the presentation of more targeted map information, such overlays are an increasingly important method of map presentation through the Internet. A multilevel overlay can be created by tiling several different maps or orthophotos. Any digital map whether a scanned historic one or a computer-generated thematic map can be converted to tiles. User-generated tiles can be overlayed on top of these maps, obscuring the standard map or satellite views. This online method of map distribution was introduced by Google in 2005 and all the major online-mapping services including Bing, Yahoo, OpenStreetMap, Nokia, and MapQuest have since adopted the technique. Splitting maps into small contiguous tiles increases the speed of Internet map distribution, improves the panning of the map, and facilitates the presentation at multiple scales.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |