GetMap Requests
A GetMap request is the WMS request you’ll use to fetch a map for use in an SOS dataset. These requests contain a lot of parameters in their queries.
http://neowms.sci.gsfc.nasa.gov/wms/wms?version=1.3.0&service=WMS&REQUEST=GetMap&LAYERS=MODAL2_D_CLD_CI&CRS=CRS:84&FORMAT=image/png&HEIGHT=1800&WIDTH=3600&TRANSPARENT=TRUE&BBOX=-180.0,-90.0,180.0,90.0&STYLES=rgb
An example GetMap request
Parameters for the GetMap Request
Permalink to Parameters for the GetMap Request- version=1.3.0
- Specifies the version of the service you’re using. Sometimes parameters and response formats can change from version to version, so services allow you to request a specific version
- service=WMS
- Identifies this request as a WMS request
- REQUEST=GetMap
- REQUEST specifies the type of WMS request you’re making. In this case, it’s GetMap
- LAYERS=MODAL2_D_CLD_CI
- Tells the server which “layer” (which map) to return. This will vary depending on the map service you use, as they all offer different data
- CRS=CRS:84
- Defines the coordinate reference system. SOS requires CRS:84
- FORMAT=image/png
- Defines the map’s format. In this case, we’re requesting the map as a PNG (an image format)
- HEIGHT=1800
- Defines the height of the image in pixels
- WIDTH=3600
- Defines the widht of the image in pixels
- TRANSPARENT=TRUE
- Sets the transparency of the map’s backgruond
- BBOX=-180.0,-90.0,180.0,90.0
- Boundary box setting defines which piece of the map you’re looking at in
degrees of latitude and longitude. For a world map, the coordinates shown
above will show the complete map. However, the SOS team prefers if users
use the parameter
<BOUNDING_BOX>
to define BBOX, like this:BBOX=<BOUNDING_BOX>
. This will always give the full map - STYLES=rgb
- Defines the “rendering style of the layer”
How to use an Existing GetMap Request
Permalink to How to use an Existing GetMap RequestIf you have an existing GetMap request already, chances are you’ll have to check a few things and change a few others. The three changes that are required, minimum, are below:
- After the HEIGHT= parameter, change whatever number is there to <IMAGE_HEIGHT>, spelled and capitalized exactly like that
- After the WIDTH= parameter, change the number to <IMAGE_WIDTH>
- After the BBOX parameter, change whatever numbers are there to <BOUNDING_BOX>
These changes are required for the SOS system, but they won’t work in a browser, because the keywords such as <IMAGE_HEIGHT> were created by the SOS team, not the designers of WMS.
You should also check a few of the parameters to make sure they’re compatible with the SOS format.
- CRS should equal CRS:84 or EPSG:4326. This parameter can’t be changed, so if it isn’t correct, you’ll need to find a different WMS server
- FORMAT should equal image/png, image/jpg, or another SOS-supported image format
If these parameters are correct, you’re good to go! See the How to Display WMS Data on the Sphere section to proceed.