These programs represent leading DoD efforts to leverage geospatial capabilities using Service Oriented Architectures and Web services. He is currently a Ph. See All Customer Reviews. Shop Books.
Add to Wishlist. USD Sign in to Purchase Instantly. Overview Tile-based mapping systems have grown to become the dominant form of mapping system with the rise of Web-based mapping tools. The origin of this book is a desire to collect all our discoveries, techniques, and best practices for creating a til- mapping system into one combined volume. The intent of this text is to provide a comprehensive guide to the theory behind creating a tiled-map system as well as a practical guide to create a concrete implementation.
About the Author Dr. Show More. Table of Contents Logical Tile Schemes. Average Review. Write a Review. Related Searches.
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Packed with checklists and real-life examples, this book provides authoritative guidance on procedures and practice Packed with checklists and real-life examples, this book provides authoritative guidance on procedures and practice in acquisitions. It approaches the acquisitions process logically through various stages, from requests through to the checking, ordering, and receipt of library materials.
This new View Product. Asparagus is a cool-season vegetable that belongs to the family Liliaceae. Botanical name of asparagus Botanical name of asparagus is Asparagus officinalis.
Tile-Based Geospatial Information Systems
It is an herbaceous perennial plant. Tender shoots spears of asparagus plants are used as a leafy vegetable. Asparagus is believed to Best Practices in Geographic Information Systems-based. PShapeObj represents initial address pointing to the space object storage address. The space object of the same node is consistent in memory storage. NChildCount represents data of child nodes contained by nodes.
Children is an array pointing to the child nodes. In a pyramid model, when the ratio of the resolution of the lower and upper map is , map tiles of tile pyramid model can be quad-tree result index storage management. Specifically from tile pyramid model layer 0, make map tiles storage paths the storage unit.
Each floor tile matrix storages successively according to the sequence of line and the use of quad-tree structure establishes the storage index. Maps are often static, since the data of every request WMS web map service is for server to process, which may lead to unnecessary treatment and increasing the waiting time. When they request, GeoWebCache optimizes storage map tiles. As the new map tiles are requested, GeoWebCache intercept these requests and pre-render tiles. If the request tiles have been stored in the cache, GeoWebCache will return to the client directly.
Therefore, once the tiles are stored, mapping speed will increase many times to realize perfect user experience. If so, request is sent to the WMS service. Then WMS service parses object request parameters, packages parameters passed by the client a tile request object and turns it to the cache manager.
If in, the cache manager will render these cached images directly to the client, otherwise it constructs standard WMS request and submits the request to the WMS Server to provide Internet map service for actual processing. Cache manager receives the result image, cuts figure, puts tiles in the cache, renders tiles and returns tiles to the client, as is shown in Fig. This experiment is based on the GeoServer Open Source map service, applying for GeoWebCache cache of improved quad-tree spatial index pyramid model to test the map publishing. Comparison of map roaming function time: Load data of the local map and roam map with three levels of province, city and country, respectively.
Table 1 shows the comparisons of the average response time conducting the same experiment 20 times. The first line is the roaming time of the map of the province, the average response time 1 indicates the client gets map tiles by requesting WMS service directly. The average response time 2 indicates the client forwards requesting map through GeoWebCache. The experimental result data in the table shows that the response time of publishing map reduces significantly based on GeoWebCache caching technology. If in, just need to forward some requests to the WMS services. Compared with the direct request, response time decreases significantly.
The method of requesting of map tiles of the second and the third lines is the same as the first line. The only difference is the range of requesting map. The effect is the same as the first line. Comparison of time of multiple threads requesting the same area simultaneously: The ratio of the map layer is M, a group of clients request the same area of the map. Because at that time there is no corresponding tiles in the cache.
Before returned, map tiles are put in GeoWebCache cache. With the increasing number of requests, GeoWebCache cache stores all requesting map tiles. So the client requests and GeoWebCache cache returns the tiles to the client directly. The response time decreases significantly as shown in Fig. But with the increasing number of requests, the response time of requesting WMS service directly is almost unchanged. Experimental result shows that using GeoWebCache caching technology reduces the response time significantly when the map server returns to the client.
Especially when the requesting map tiles are all in the GeoWebCache cache, the response time changes more evident and it reduces the load on the server at the same time. If in, the cache manager renders these cached images directly to the client and the response time reduces significantly, otherwise it constructs standard WMS request and submits the request to the WMS Server to provide Internet map service for actual processing.
So the response time and the load on the server reduces significantly by using the GeoWebCache caching technique of pyramid model based on quad-tree spatial index. The present research of technology of instantaneously generated map tiles leads to that the server response time is long, with low efficiency and big consumption of server resource. However, according to experimental results, using the GeoWebCache caching technique of pyramid model based on quad-tree spatial index not only improves the efficiency of the map tiles to return but also reduce the server overhead and improve the user experience greatly.
But due to the limitations of the experimental data, further demonstration of the reliability and stability of the experimental results under high concurrency need to be discussed in the future. Du, Q. Yu and F. Ren, Organization tile map data based on nested pyramids model. Wuhan Univ. Huang, N. Pan and J.
Kang, A new dynamic tile caching method for WebGIS.
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