GetCoverage Operation |
The GetCoverage action is required.
The GetCoverage operation, which allows clients to retrieve subsets of Coverage, typically follows the GetCapabilities and DescribeCoverage operations. Because through these two operations, the client can know which requests are allowed by the server and what data is available. The GetCoverage operation eventually returns some raster data within a specified field value in a specified geographic range.
The client can send a KVP encoded Get request.
The main request parameters for the Get Coverage operation are shown in the following table:
Table 1 Main Parameters of Get Coverage Operation Request
| Request parameters | Whether it is required | Description |
| SERVICE=WCS |
Yes |
Service type Request WCS service. The request type needs to be set to " WCS ". |
| REQUEST=GetCoverage |
Yes |
Request name. A Get Coverage operation was requested. The request name needs to be set to "GetCoverage". |
|
Version |
Yes |
The version of the requested WCS service. |
|
Identifier |
Yes |
Specifies the unique identifier of the Coverage to be requested. |
|
DomainSubset |
Yes |
Defines the spatio-temporal scope of the requested Coverage. Contains two parameters: BoundingBox (required) and TemporalSubset (optional). The former specifies the geographical range and the latter the appointed day range. |
|
RangeSubset |
No |
Defines the range of values for which Coverage is requested. |
|
Output |
Yes |
Specify the output settings. It includes GridCRS (geographic reference system for returning data, optional) and Format (format for returning data, supporting PNG and GeoTiff formats). Required) and Store ( "true" indicates that the server is required to store all contents of the returned data in a network location and return its URL; "false" indicates that the server is required to directly return the data; optional). |
Note: The case of the parameters is not required, and the order of the request parameters can also be arranged in any order.
Among them, RangeSubset defines a certain range of coverage expected by the client, such as for grid elevation data or temperature data, this parameter can only return data within a certain range of elevation or temperature. RangeSubset consists of one or more FieldSubsets, and the specific parameters of FieldSubsets are detailed in the table below.
Table 2 Main parameters of FieldSubset
| Request parameters | Whether it is required | Description |
|
Identifier |
Yes |
Name of the requested value field range. |
|
InterpolationType |
No |
The spatial interpolation method used for data resampling within the requested range. |
|
AxisSubset |
No |
When the value domain is a vector domain, it can be used to define the scale values on the requested vector domain axes. It is defined by two parameters, Identifier and Key. |
The Get Coverage operation is requested as follows:
<ServiceRoot>?SERVICE=WCS&REQUEST=GetCoverage&Version=1.1.2&Identifier=Day@World&BoundingBox=&Format=
ServiceRoot is the URI root directory of the service. Please refer to URI settings .
For example, after the local iServer service is started, the GetCapabilities and DescribeCoverage operations on the data-world/wcs112 service are performed to obtain the information in the service Day@World At this point, the relevant information can be obtained through ∝verage Day@World The data within the specified range is as follows:
http://localhost:8090/iserver/services/data-world/wcs112?SERVICE=WCS&REQUEST=GetCoverage&Version=1.1.2&Identifier=1&Boun dingBox=-90,-180,90,180,urn:ogc:def:crs:EPSG::4326&Format=image/png&Store=true
Response results, see Response example .
According to the parameters in the request sent by the client, the server returns eligible data in the format specified by Format in Output, and returns the meta-information related to the data.
The request data meta info returned by the server is shown in the following table.
Table 3 Meta-information of Response Data
| Element Name | Whether it is required | Description |
|
BoundingBox |
Yes |
Returns the bounding box of the data. |
|
GridCRS |
No |
If a georeferencing system is used in the bounding box, this CRS needs to be specified. |
|
Transformation |
No |
If the returned data is not geo-corrected but projected, the projection method needs to be indicated. |
After executing the GetCoverage operation, the response in XML format returned by the server is as follows:
Go to the"http://127.0.0.1:8090/iserver/output/temp/25139431/Day_-1018300774.png"，to get th Coverage data in PNG format.