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<!------------------------------- STEP 1 --------------------------->
<!-- Fill in the details (CodeProject will reformat this section for you) --><pre>Title: Free Maps from the Web Using Web Mapping Service
Author: Tom Gaskins
Email: tom@tomgaskins.com
Environment: VC#, VS/MSDE 2003, .Net 1.1, WinXP
Keywords: Maps, OpenGIS, Data Visualization, Graphics
Level: Intermediate
Description: Overview of using the OpenGIS Web Mapping Service to retrieve maps from the web.
Section General C# Programming
SubSection Graphics
</pre>
<!------------------------------- STEP 2 --------------------------->
<!-- Include download and sample image information. -->
<ul class="download">
<li>
<A href="WMSOverviewSolution.zip">Download WMS Overview solution with source - 310
Kb </A>
</li>
<li>
<A href="WMSOverviewExamples.zip">Download WMS Overview example binaries - 55 Kb </A>
</li>
</ul>
<p><IMG height="350" alt="Sample image of WMS browser and a preview map." src="WMSOverviewFigure01.gif"
width="590"></p>
<!------------------------------- STEP 3 --------------------------->
<!-- Add the article text. Please use simple formatting (<h2>, <p> etc) -->
<h2>Abstract</h2>
<P>This tutorial introduces the Web Mapping Service (WMS) protocol standardized by
the OpenGIS Consortium for retrieving geographic maps over the internet. The
tutorial provides C# examples of progressively increasing complexity to
illustrate use of the protocol and programmatic access from Windows .Net
applications. Several utility classes for accessing WMS servers and information
are provided and described.</P>
<H2>Introduction</H2>
<p>An amazing number of free, interesting, and just plain beautiful geographic maps
are available on the web, and they can be easily retrieved programmatically
using the Web Mapping Service protocol developed by the OpenGIS consortium (<A href="http://www.opengis.org">www.opengis.org</A>
). For example, follow the link below to retrieve a world map of today's
highest temperatures. Come back here afterwards to learn how it works.
<P><A href="http://viz.globe.gov/viz-bin/wmt.cgi?SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&LAYERS=COASTLINES,RATMAX&STYLES=,&BBOX=-180,-90,180,90&SRS=EPSG:4326&FORMAT=image/gif&HEIGHT=300&WIDTH=600">http://viz.globe.gov/viz-bin/wmt.cgi?SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&LAYERS=COASTLINES,RATMAX&STYLES=,&BBOX=-180,-90,180,90&SRS=EPSG:4326&FORMAT=image/gif&HEIGHT=300&WIDTH=600</A>
<P>
The map you saw in your browser should have looked something like this, which
shows the world's maximum temperatures on April 23, 2004:
<p><IMG height="300" alt="Image of world's maximum temperatures today." src="WMSOverviewFigure02.gif"
width="600"></p>
<P>The URI you just followed is an example of a Web Mapping Service (WMS) GetMap
request. Each element of the URI is a defined parameter of the WMS protocol:
The base path of the URI identifies the WMS server; the query sting specifies
the desired maps and how to represent them. There are additional parameters
possible, but the ones above are the required ones.</P>
<P>This article gives an overview of WMS, and it presents C# code to retrieve maps
and perform other operations necessary when working with WMS servers and
information.</P>
<P>
<h2>The Web Mapping Service Protocol</h2>
<p>WMS is a web protocol created by the OpenGIS Consortium as a standard way to
request and deliver geographic maps and associated information over the web.
Data providers and application developers are increasingly adopting WMS. The
full WMS specification is available at <a href="http://www.opengis.org/specs/?page=specs">
www.opengis.org/specs/?page=specs</a>. The most commonly implemented
version is version 1.1.1, but there are still some servers stuck at version
1.0. The next version, 1.3, (version number 1.2 was skipped) is in development
as of April 2004. As standards go, the WMS standard is not hard to read, and
it's blessedly short. Give it a look when you're done reading this article. It
contains information essential to using WMS, and it's free! A WMS discussion
list exists at <a href="http://mail.digitalearth.org/mailman/listinfo/wms-dev">mail.digitalearth.org/mailman/listinfo/wms-dev</a>
. There's a link to a WMS FAQ on that page, too.
<P>A WMS request is an HTTP-GET message sent to a WMS server. The WMS specification
defines three request types: GetCapabilities, GetMap, and GetFeatureInfo.
You'll find that you use the first two almost exclusively. These two request
types are the only ones you need to achieve all the functionality described in
this tutorial.
<h2>Determining the Available Maps</h2>
<p>The maximum temperature is one of the many maps available from institutions that
receive raw data and process it into geographic information displays. The link
two sections above accesses the NASA GLOBE Visualization server (see <a href="http://www.globe.gov">
www.globe.gov</a>
), which provides comprehensive information on the world's environment and is
updated daily. This information comes from space-based and land-based
instruments, as well as teams of students around the world who collect local
data.
<P>How do you determine where to find WMS servers? And how do you learn what maps
are available? The last question is the easiest to answer: Every WMS server
provides upon request an XML document, called the server's WMS capabilities
description, that describes all the maps that server can generate, and all the
details and available variations you can request for those maps. The document
also identifies the URIs for programmatically accessing the maps. Typically,
the capabilities description is updated daily to reflect new data. To see the
Capabilities document for the GLOBE server as of April 23, 2004, open <A href="GLOBECapabilities20040423.xml">
this file (GLOBECapabilities2
GIS解析WMS服务程序
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C#开发，可解析WMS服务，并进行浏览，功能强大，GIS开发人员可参考 .zip （60个子文件） 
Get Map Example 
Get Map Example.csproj 4KB GetMapExample.cs 3KB App.ico 1KB AssemblyInfo.cs 2KB Get Map Asynch Example GetMapAsynchExample.resx 7KB GetMapAsynchExample.cs 9KB App.ico 1KB Get Map Asynch Example.csproj 5KB AssemblyInfo.cs 2KB
WMSOverviewFigure01.gif 78KB Get Capabilities Example GetCapabilitiesExample.cs 1KB Get Capabilities Example.csproj 4KB App.ico 1KB AssemblyInfo.cs 2KB WMS Overview.sln 4KB WMSOverviewFigure03.gif 106KB WMSOverviewFigure02.gif 23KB MapAnimation MapAnimation.resx 9KB App.ico 1KB Map Animation.csproj 5KB MapAnimation.cs 9KB AssemblyInfo.cs 2KB GLOBECapabilities20040423.xml 136KB Wms.Client WmsException.cs 1KB
CLSDFOLD.BMP 246B ExtensionMap.cs 2KB DefaultServerDescriptors.xml 748B Capabilities.cs 10KB WmsServerDescriptors.cs 13KB WmsServerDescriptors.xsx 193B OPENFOLD.BMP 246B WmsDialog.cs 54KB PreviewDialog.resx 8KB DownloadCache.cs 9KB ServerAddDialog.resx 14KB Wms.Client.csproj 9KB ENTIRNET.BMP 246B Layer.cs 24KB WmsDialog.resx 27KB ENTIRNETX.ICO 1KB Retriever.cs 14KB RequestBuilder.cs 7KB PreviewDialog.cs 4KB EARTH.ICO 1KB ServerDescriptor.cs 634B ENTIRNET.ICO 1KB ENTIRNETX.bmp 248B WmsServerDescriptors.xsd 791B ServerAddDialog.cs 6KB Server.cs 781B AssemblyInfo.cs 2KB WMSBrowser WMSBrowser.csproj 5KB MapForm.resx 7KB App.ico 1KB WMSBrowser.resx 6KB WMSBrowser.cs 2KB MapForm.cs 2KB AssemblyInfo.cs 2KB
www.pudn.com.txt 218B
WMS Overview Article.html 64KB
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