GetCoverage Operation |
The GetCoverage operation is a necessary operation.
The GetCoverage operation allows retrieval of subsets of Coverages. The GetCoverage operation is normally run after GetCapabilities and DescribeCoverage operation responses have shown what requests are allowed and what data are available. The GetCoverage operation finally returns the raster data of the specified ranges in the specified geographic range.
WCS clients can send Get request using KVP encoding.
The main request parameters of GetCoverage operation are shown in the following table:
Table 1 Parameters in GetCoverage operation request
| Request parameters | Required/Optional | Description |
| SERVICE=WCS |
Mandatory |
Service type. Request WCS service.Shall be "WCS". |
| REQUEST=GetCoverage |
Mandatory |
Request names. Name of the operation, shall be "GetCoverage". |
|
Version |
Mandatory |
Specification version for operation. |
|
Identifier |
Mandatory |
Unique identifier of an available coverage. |
|
DomainSubset |
Mandatory |
Defines desired subset of domain set of identified Coverage. Includes BoundingBox (mandatory) and TemporalSubset (optional) parameters, and the former specifies spatial subset of coverage and the later specifies the temporal subset of coverage. |
|
RangeSubset |
Optional |
Defines the range of values of the request Coverage. |
|
Output |
Mandatory |
Specifies desired output options. Includes GridCRS (Definition of Coordinate Reference System in which GetCoverage operation response shall be expressed and optional ) , Format (Identifier of format in which GetCoverage operation response shall be encoded and mandatory) and store ("True" value asks server to store all components of the response coverage in a Web-accessible location, referenced by URL(s) in the GetCoverage response. "False" value asks server to return all components of the response coverage synchronously, bundled with the GetCoverage response. It is optional). |
Explanation:The case of the parameters is not important and the order of the request parameters can be random.
RangeSubset defines the range of values of the client is desired. For example, it will return several data in all range fields for grid and temperature data. RangeSubset is composed of one or more FieldSubset and the details of parameters is shown in the following table.
Table 2 Parameters in FieldSubset
| Request parameters | Required/Optional | Description |
|
Identifier |
Mandatory |
Name of requested field. |
|
InterpolationType |
Optional |
Spatial interpolation method to be used to resample values in this field. |
|
AxisSubset |
Optional |
Desired keys in one Axis for one (vector) field. Defines through the Identifier and Key parameters. |
The method of GetCoverage operation request is in the following way:
<ServiceRoot>?SERVICE=WCS&REQUEST=GetCoverage&Version=1.1.2&Identifier=Day@World&BoundingBox=&Format=
ServiceRoot is the URI root directory of service and refer to the URI setting of service。
After started the iServer service, obtain the service Day@World information through GetCapabilities and DescribeCoverage operation and obtain the specified range data of Day@World through GetCoverage operation.
Response results, please refer to response example.
The server returns the eligible specified format data in Output and the related metadata according to the parameters requested by the client.
The metadata of request data returned by the service is shown in the following table.
Table 3 Metadata of response data
| Names | Required/Optional | Description |
|
BoundingBox |
Mandatory |
Bounding box that specifies extent of output coverage. |
|
GridCRS |
Optional |
If the georeferencing coordinate system used in the bounding box, the CRS need to be specified. |
|
Transformation |
Optional |
The projection way must be specified if the returned data does not perform geographical correction but projection. |
The server will return the response in the xml format after performed the GetCoverage operation.
Refer to 'http://127.0.0.1:8090/iserver/output/temp/25139431/Day_-1018300774.png' for coverage data in the png format.