WMS GetMap GetCapabilities 参数详解

http://oceanesip.jpl.nasa.gov/esipde/guide.html

Online Viewer:

http://its.demo.galdosinc.com/wms/viewer/#

WMS source:
http://labs.metacarta.com/wms/vmap0
http://www2.demis.nl/mapserver/request.asp

Online sample:
http://openlayers.org/dev/examples/lite.html
http://trial.parcelstream.com/client/ver0_75/Samples/GoogleExternalWMSSample.html
http://wms-sites.com/catalog/Intergraph-US-sample-WMS/counties/

Guide to Distributing Your Data Products Via
WMS 1.1.1

A Tutorial for Data Providers

By Rob Raskin, Ocean ESIP, Jet Propulsion Lab

http://oceanesip.jpl.nasa.gov/esipde/guide.html
(Last updated Jan 2004)

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This document provides assistance to data providers who would like to distribute their data products via the Web Mapping Server (WMS) protocol. This protocol was developed by the Open GIS Consortium (OGC) as a standard for transferring maps and georeferenced data over the Internet. If your data server complies with this standard, then users will be able to visualize your images or maps using a standard Web browser. Furthermore, users can overlay your products with other georeferenced maps, data, and imagery using a custom viewer.

If you are already providing spatial/temporal subsets from a web server, then WMS-compliance is relatively simple. Compliance involves a minimum of absolute requirements, plus several optional services. To be compliant, you must be able to deliver the following products via HTTP upon request:

1) User-selected spatial subsets (the GetMap request )
2) Metadata in an XML file (the GetCapabilities request).

You also must be able to deliver any error messages to the client in an XML file, in the event that either of the above requests are not satisfiable.

The first sections of this Guide detail the minimum requirements of WMS compliance. Later sections describe optional services that you may choose to provide beyond the minimum requirements.

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GetMap

A WMS server must be able to deliver a map via http upon receiving a client request such as the following:

http://www.airesip.org/wms/process.cgi?REQUEST=GetMap&FORMAT=image/gif&WIDTH=640&HEIGHT=480&
LAYERS=temperature&SRS=EPSG:4326&BBOX=-110.,40.,-80.,30.&VERSION=1.1.1

In this hypothetical example, www.airesip.org is the server hostname, wms/ is its directory path, and process.cgi is the name of the CGI script processing the client requests. You can choose the directory path and file names. A question mark is appended after the script name to separate it from the parameter list. The parameter list consists of parameter name=value assignments separated by a an ampersand (&).

Parameters may appear in any order. Parameter names are not case-sensitive; therefore, height=480 and HEIGHT=480 are identical requests. However, you may choose to interpret parameter values as case-sensitive. No spaces appear anywhere in the request string. A description of each parameter is given below:

REQUEST
The parameter REQUEST=GetMap indicates that this request is for a map.

FORMAT
You choose which output formats to support. Permissible image formats include: image/gif, image/jpeg, image/tiff, image/geotiff, image/png, image/ppm, and image/wbmp. Several public domain and commercial software packages for creating images from numerical data will be listed in a future version of this Guide. (Note that TIFF and GeoTIFF support floating point data types as well as 16-bit integers, although not all TIFF/GeoTIFF readers support these features.)

WIDTHand HEIGHT
You must be able to provide images in any requested size. These values will be requested as positive integers.

LAYERS
You choose which layers (variables) to provide and how they are named. You must be able to receive a request for multiple layers (e.g. LAYERS=temperature,coastline,cities). In this example, temperature is drawn first, coastline is drawn on top of temperature, followed by cities.

SRS
You choose the map projection (or spatial reference system) (SRS) in which to deliver your data products. The SRS is commonly expressed in terms of its European Petroleum Survey Group (EPSG) numeric code. The