Caching Tile Cache Creation & Management

Transcription

1 Exploring Options for Map Caching Tile Cache Creation & Management Presented By: Todd Wascher, Business Development Manager We Visualize Your World

2 Whachutalkinbout? What we ll cover with this session: An Overview Caching Explained (briefly) General Benefits of Map Caching Some Caching Terms and Concepts A Comparison of Available Tools Mapproxy, Tilecache, GeoWebCache, ArcGIS Server Functionality & Capabilities of Each Summary & Conclusion Choosing the Right Tool for the Job Consuming and Utilizing Cached Mapservices

3 Caching Overview Well, what is map caching? What types of things can I cache? Got any Examples?

4 Caching Overview What are some benefits of having a cached mapservice? Lighten Browser load Lighten Server load Requests for small images rather than dynamic data rendering Potential to improve performance

5 Caching Terms & Concepts Seeding Metatiling Tiling Schemes Image Types Transparency Projections / Reprojection

6 Caching Terms & Concepts Seeding Seeding is basically pre rendering rendering ordynamically creating maptiles based upon a defined extent or a geometry. Seeding actions can be scripted, generated on the fly (user requests) or manually created.

7 Caching Terms & Concepts Metatiling A metatile consists of several tiles combined into one larger tile. Pros: Avoid duplicating the labeling of features that span more than one tile Usually quicker for the WMS backend to generate one large image rather than many small ones Cons: Since the metatile is larger, it is slower to render than any individual tile Memory consumption

8 Caching Terms & Concepts Tiling Schemes Tiling schemes allow for definition of scale levels, tile size and sometimes coordinate system. Setting tiling schemes for ArcGIS Server vary greater than the other optionswe will review.

9 Caching Terms & Concepts Image Types Cached map tiles can be created/requested in different image formats. Most commonly.png for transparency and.jpeg for imagery. Transparency Transparency is used for overlaying tiles on top of other tiles and for sliding/transitioningeffects effects. Supportedwith.png. Also parameter in WMS request. Projections / Reprojection Most caches are created in a defined projection, but some utilities can reproject tiles (mapproxy).

10 How? ConsumingWMS andchopping it upinto tiles Stored in accessible directory to be returned to client Application requests handled by cache utility Projection Location Tile size Image format

11 Comparison of Caching Utilities

12 MapProxy MapProxy is an open source proxy for geospatial data. It caches, accelerates and transformsdata from existing map services and serves any desktop or web GIS client. MapProxy works like a simple tile cache, but also offers many new and innovative features like full support for WMS clients. MapProxy is an open source technology used to create and serve up map caches. It is a middle man man between existing web map servers (like MapServer or GeoServer) and web map clients such as OpenLayers and GoogleEarth.

13 TileCache TileCache is an implementation of a WMS C compliant server made available under the BSD (Berkeley Software Distribution) license by MetaCarta. TileCache provides a Python based WMS C/TMS server, with pluggable caching mechanismsandrenderingbackends and backends. Inthe simplestusecase case, TileCache requires only write access to a disk, the ability to run Python CGI scripts, and a WMS you want to be cached. With these resources, you can create your own local disk based cache of any WMS server, and use the result in any WMS C supporting client, like OpenLayers, or any TMS supporting client, like OpenLayers and worldkit.

14 GeoWebCache GeoWebCache is a Java web application used to cache map tiles coming from a variety of sources such as OGC Web Map Service (WMS). It implements various service interfaces (such as WMS-C, WMTS, TMS, Google Maps KML, Virtual Earth) in order to accelerate and optimize map image delivery. It can also recombine tiles to work with regular WMS clients.

15 A Matrix

16 So, ArcGIS Server already has Caching Tools Single mapservice focus GUI / Geoprocessing options Tailored dfor esri APIs Compact Cache

17 Choose the Right Tool for the Job All caching utilities are basically reading a mapservice, taking a snapshot of it and cutting it up into tiles defined by the user/tool. Once the tiles are created, they are stored in a directory structure similar to: Cache directory Name of service Scale levels Row Column Image Thi h li h l b d h l i d i h j b b i ll il This may change slightly based on what tool is doing the job, but typically tiles are sliced and stored around the grid based system of level, row, column.

18 Utilizing Cached Services Web Applications ArcGIS Desktop Geoportals/Opendata

19 Resources Links! org/ /index.html#/what_is_map_caching/ m000000/ is map

20 Thanks! Feel free to ask any questions or share your own tips WeDoGIS Todd.Wascher@adc4gis.com