Some of FengYun satellite image products are providing image API service following the standard WMS (Web Map Service). It deals with the request sent by user clients, processes FengYun satellite image products and returns a whole picture to the user clients for further programming and integration.
This service includes two interfaces: "GetCapabilities" which returns detail descriptions of the service's contents and parameters, and "GetMap" which returns a picture after processing the FengYun image products.
The GetCapabilities interface returns a WMS-standard XML, containing the metadata of image API service on request.
GetCapabilities request parameters
| Parameter | Optional | Description |
|---|---|---|
| REQUEST | Required | Nam of the request. Must be "GetCapabilities". |
An example of GetCapabilities request is as following:
The response of "GetCapabilities" request will be in XML format, containing the "Service" and "Capability" contents.
The "Service" contents are a general description of the service's metadata.
Service metadata elements:
| Element | Description |
|---|---|
| Name | Name of the WMS service. |
| Title | A brief description of the service. |
| Abstract | Detailed informations. |
| OnlineResource | The reference website. |
| KeywordList | Keyword | Keywords. |
| ContactInformation | Contact information. |
| LayerLimit | Maximum number of layers that can be requested. A positive integer. |
| MaxWidth & MaxHeight | Maximum width and height of requested pictures. Two positive integers. If any one of them is not defined, no restrains will be taken. |
| Fees | "none" (case-insensitive) means free of fees. |
| AccessConstraints | Constraints of access."none" (case-insensitive) means no constraints. |
The "Capability" contents are consisted with "Request" information and "Layer" information.
——"Request": URL, format, etc. of supported request ("GetCapabilities", "GetMap" or "GetFeatureInfo").
——"Layer": elements and properties as shown below:
Layer Elements:
| Element | Required | Description |
|---|---|---|
| Title | Required | Title of the layer. Can NOT be inherited by sub-layer(s). |
| Name | Optional |
Name of the layer. Can NOT be inherited by sub-layer(s). This should be used in "GetMap request"as the correct value of "LAYERS" parameter. |
| Abstract | Optional | Abstract of the layer with more detailed descriptions. Can NOT be inherited by sub-layer(s). |
| KeywordList | Optional | List of keywords. Can NOT be inherited by sub-layer(s). |
| Style | Optional |
Style(s) of the layer(s). Will be automatically inherited by sub-layer(s). Each "Style" contains "Name" for setting the "STYLES" parameter in "GetMap" request and "Title" element. "Style" may contain other elements: "Abstract" for description of the style, "LegendURL" for position of the legend image. "LegendURL" has sub-elements: "Format" for MIME type of the legend image, whose "width" and "height" properties" defines the number oif pixels of the legend image. |
| EX_GeographicBoundingBox | Optional |
Geographic bounding box. Can be inherited from its parent layer. Each named layer has an "EX_GeographicBoundingBox" element in decimal degree to define the minimum bounding box it covers. This element if composited by "westBoundLongitude", "eastBoundLongitude", "southBoundLatitude" and "northBoundLatitude" |
| CRS | Required |
Coordinate Reference System. Can NOT be inherited by sub-layer(s). Each layer has at least one CRS. CRS root contains 0 or multiple CRS elements, listing all CRS that are applied to sub-layer(s)。 |
| BoundingBox | Required |
Bounding box. Can be inherited from its parent layer. Each layer has at least one Bounding box, contains the following properties:
"BoundingBox" element in metadata defines the range of the layer, while the "BBOX" parameter in GetMap request defines the requested image area. |
| MinScaleDenominator & MaxScaleDenominator | Optional |
Min-and max scale of the denominator. If neither of these two elements exist, there will be no constrains to the denominator. |
| Dimension | Optional | Applied to multi-dimensional data. Inherited from its parent layer. |
| MetadataURL | Optional | URL of detailed descriptions of the metadata. Can NOT be inherited by sub-layer(s). |
| Attribution | Optional |
The information source of information of the layer(s). Can NOT be inherited by sub-layer(s).
|
| Identifier & AuthorityURL | Optional | A list of authority IDs or tags. |
| FeatureListURL | Optional | URL of feature lists. |
| DataURL | Optional | URL of related datasets. Can NOT be inherited by sub-layer(s). |
Layer Element properties:
| Property | Acceptable Values | Meaning (default value is 0) |
|---|---|---|
| queryable | 0, false, 1, true |
0, false: the layer can NOT be requested. 1, true: the layer can be requested. |
| cascaded | 0, positive integer |
0: the layer has been cascaded by Cascading Map Servers. n: the layer has been cascaded n times. |
| opaque | 0, false, 1, true |
0, false: the returned picture is partially opaque. 1, true: the returned picture is totally opaque. |
| noSubsets | 0, false, 1, true |
0, false: draw a subset of the boundary box. 1, true: draw the entire boundary box. |
| fixedWidth | 0, positive integer |
0: return a picture with arbitrary width. non-0: return a picture with fixed width. |
| fixedHeight | 0, positive integer |
0: return a picture with arbitrary width. non-0: return a picture with fixed width. |
GetMap request parameters
| Parameter | Required | Description |
|---|---|---|
| VERSION | Yes | Version of request. Current version is "1.3.0". |
| REQUEST | Yes | Name of request. Must be "GetMap". |
| LAYERS | Yes | List of layers. Should be acquired by GetCapability request. For example, "FY3D_MERSI" or "GEOS_IRX". |
| DATETIME | Yes | Date and time (UTC). Should be in "YYYYMMDDhhmm" format for hourly products and in "YYYYMMDD" format for daily products. |
| BBOX | Yes | Range of the boundary box Should be four real numbers separated by commas, such as "minx,miny,maxx,maxy", representing respectively the minimum longitude, minimum latitude, maximum longitude and maximum latitude of the area under certain coordinations CRS. Incorrect BBOX can be caused by "minx" is not smaller than "maxx", "miny" is not smaller than "maxy", and so on. If the requested BBOX has no overlap with the "BoundingBox" defined in the metadata, an empty picture will be returned. |
| WIDTH | Yes | Width of the requested picture in pixel. |
| HEIGHT | Yes | Height of the requested picture in pixel. |
| FORMAT | Yes | Format of the requested picture. |
An example of GetMap request for FY-3 MERSI global image is as following:
where "DATETIME" is "20220801" as 2022 August 1st (UTC), "BBOX" is "100,10,120,30" as "100~120°E, 10~30°N".
An example of GetMap request for global GEO mosaic image is as following:
where "DATETIME" is "202208011300" as 2022 August 1st 13:00 (UTC), "BBOX" is "90,0,135,45" as "90~135°E, 0~45°N".
To a correct GetMap request, the server returns a picture as requested.
To an incorrect GetMap request, the server returns an empty picture.