OGC标准介绍 17

I. WCS- 栅格Web服务

· 概述

WCS（OpenGIS® Web Coverage Service）当前版本是1.1.2。WCS标准定义了一些操作，这些操作允许用户访问“Coverage”数据，如卫星影像、数字高程数据等，也就是栅格数据。

· WCS 的操作

WCS包括以下3个操作：

1. GetCapabilities（获取服务的元信息）

2. DescribeCoverage（获取Coverage的描述信息）

3. GetCoverage（获取Coverage）

关于服务涉及的基本元素，可以参考前面的章节：《服务涉及的基本元素》。

· GetCapabilities 操作

1. KVP格式请求

GetCapabilities操作需要以下的参数：

参数	是否必须	默认值
SERVICE	是	WCS
REQUEST=GetCapabilities	是
ACCEPTVERSIONS
SECTIONS
UPDATESEQUENCE
ACCEPTFORMATS

以下是一个WCS使用KVP格式的GetCapabilities操作示例：

http://hostname:port/path?

service=WCS&

request=GetCapabilities

2. XML格式请求

以下是一个WCS使用XML格式的GetCapabilities操作示例：

xml version="1.0" encoding="UTF-8"?>




<
GetCapabilities
 xmlns
="http://www.opengis.net/wcs/1.1.1"




xmlns
:xsi
="http://www.w3.org/2001/XMLSchema-instance"




xsi
:schemaLocation
="http://www.opengis.net/wcs/1.1.1 ../wcsGetCapabilities.xsd"




service
="WCS"
 />

      

3. 响应示例

以下是一个WCS的GetCapabilities操作的响应示例：

xml version="1.0" encoding="UTF-8"?>




<
wcs
:Capabilities
 xmlns
="http://www.opengis.net/wcs/1.1"




xmlns
:ows
="http://www.opengis.net/ows/1.1"
 xmlns
:xsi
="http://www.w3.org/2001/XMLSchema-instance"




xsi
:schemaLocation
="http://www.opengis.net/wcs/1.1 ../wcsDescribeCoverage.xsd http://www.opengis.net/ows/1.1 ../../../ows/1.1.0/owsAll.xsd"
>




<
ows
:ServiceIdentification
>




<
ows
:Title
>
Web Coverage Service
    ows
:Title
>




<
ows
:Abstract
>
WCS
     ows
:Abstract
>




<
ows
:ServiceType
>
WCS
      ows
:ServiceType
>




<
ows
:AccessConstraints
>
NONE
       ows
:AccessConstraints
>





        ows :ServiceIdentification > 
 
 < ows :OperationsMetadata > 
 
 < ows :Operation name ="GetCapabilities" > 
 
 ...
 
 
         ows :Operation > 
 
 < ows :Operation name ="DescribeCoverage" > 
 
 ...
 
 
          ows :Operation > 
 
 < ows :Operation name ="GetCoverage" > 
 
 ...
 
 
           ows :Operation > 
 
 < ows :Constraint name ="PostEncoding" > 
 
 < ows :AllowedValues > 
 
 < ows :Value > XML
            ows :Value > 
 
 
             ows :AllowedValues > 
 
 
              ows :Constraint > 
 
 
               ows :OperationsMetadata > 
 
 < wcs :Contents > 
 
 ...
 
 
                wcs :Contents > 
 
 
                 wcs :Capabilities >          





      

· DescribeCoverage 操作

1. KVP格式请求

DescribeCoverage操作需要以下的参数：

参数	是否必须	默认值
VERSION	是	1.1.2
SERVICE	是	WCS
REQUEST=DescribeCoverage	是
IDENTIFIERS	是

以下是一个WCS使用KVP格式的DescribeCoverage操作示例：

http://server_address/path/script?

service=WCS &

request=DescribeCoverage&

version=1.1.2 &

identifiers=Cov1,Cov2,Cov3

2. XML格式请求

以下是一个WCS使用XML格式的DescribeCoverage操作示例：

xml version="1.0" encoding="UTF-8"?>




<
DescribeCoverage
 xmlns
="http://www.opengis.net/wcs/1.1"




xmlns
:xsi
="http://www.w3.org/2001/XMLSchema-instance"




xsi
:schemaLocation
="http://www.opengis.net/wcs/1.1 ../wcsDescribeCoverage.xsd"




service
="WCS"
 version
="1.1.2"
>




<
Identifier
>
Cov1
    Identifier
>




<
Identifier
>
Cov2
     Identifier
>




<
Identifier
>
Cov3
      Identifier
>





       DescribeCoverage
>





      

3. 响应示例

以下是一个WCS的DescribeCoverage操作的响应示例：

xml version="1.0" encoding="UTF-8"?>




<
CoverageDescriptions
 xmlns
="http://www.opengis.net/wcs/1.1"




xmlns
:ows
="http://www.opengis.net/ows/1.1"
 xmlns
:xsi
="http://www.w3.org/2001/XMLSchema-instance"




xsi
:schemaLocation
="http://www.opengis.net/wcs/1.1 ../wcsDescribeCoverage.xsd http://www.opengis.net/ows/1.1 ../../../ows/1.1.0/owsAll.xsd"
>




<
CoverageDescription
>




<
ows
:Title
>
TBD
    ows
:Title
>




<
ows
:Abstract
>
TBD
     ows
:Abstract
>




<
Identifier
>
TBD
      Identifier
>




<
Domain
>




<
SpatialDomain
>




<
ows
:BoundingBox
>




<
ows
:LowerCorner
>
-30.00 -30.00
       ows
:LowerCorner
>




<
ows
:UpperCorner
>
30.00 30.00
        ows :UpperCorner > 
 
 
         ows :BoundingBox > 
 
 
          SpatialDomain > 
 
 
           Domain > 
 
 < Range > 
 
 < Field > 
 
 < ows :Title > TBD
            ows :Title > 
 
 < ows :Abstract > TBD
             ows :Abstract > 
 
 < Identifier > TBD
              Identifier > 
 
 < Definition > 
 
 < ows :AnyValue /> 
 
 
               Definition > 
 
 < InterpolationMethods > 
 
 < InterpolationMethod > linear
                InterpolationMethod > 
 
 < Default > cubic
                 Default > 
 
 
                  InterpolationMethods > 
 
 
                   Field > 
 
 
                    Range > 
 
 < SupportedCRS > urn:ogc:def:crs:EPSG::XXXX
 
 
                     SupportedCRS > 
 
 < SupportedCRS > urn:ogc:def:crs:EPSG::YYYY
 
 
                      SupportedCRS > 
 
 < SupportedFormat > text/xml
                       SupportedFormat > 
 
 
                        CoverageDescription > 
 
 
                         CoverageDescriptions >