THREDDS Data Server: ncWMS and WCS
NetCDF Web Map Service (ncWMS) and Web Coverage Service (WCS) through NCI THREDDS
For more information on WMS and WCS standards specifications and ncWMS: <br > http://www.opengeospatial.org/standards/wms <br > http://www.opengeospatial.org/standards/wcs <br > http://www.resc.rdg.ac.uk/trac/ncWMS/ <br >
1. NetCDF Web Map Service (ncWMS)
Navigate to the dataset THREDDS catalog page
Click on the WMS link
GetCapabilities
This will display the WMS 'GetCapabilities' request in xml, which describes the WMS parameters (metadata, services, and data) available by the server. These options are used to generate a GetMap request, an operation which requests that the server generate a map.
GetCapabilities example:
GetMap
Several WMS tools accept the GetCapabilities URL and allow users to interactively generate a GetMap request
Note: This results in a map request built with the default settings, colormaps and scales (or time steps) may not be defined appropriately.
The more explicit option is to directly build the full GetMap request using the information displayed in the GetCapabilities response
GetMap parameters:
| Parameter | Required/Optional | Input |
|---|---|---|
| service | Required | WMS |
| version | Required | 1.1.1**, 1.3.0 |
| request | Required | GetMap |
| Layers | Required | <variable> |
| crs | Required | <crs_value> |
| styles | Required | <style_name> |
| format | Required | image/png , image/png;mode=32bit , image/gif , image/jpeg |
| bbox | Required | <ymin,xmin,ymax,xmax> |
| width | Required | Image width in pixels |
| height | Required | Image height in pixels |
| colorscalerange | Optional | <min,max> |
| transparent | Optional | True, False |
| time | Optional | <time_value> |
Syntax differences for v1.1.1 GetMap requests:
Use
srsin place ofcrsThe order of
bboxvalues is:<xmin,ymin,xmax,ymax>
GetMap request example:
The GetMap request can be tested by inserting the URL into a web browser:
Some known issues:
The
'time'parameter is not supported in all tools and will only display data from the default time step specified in the GetCapabilities xml.
Web Coverage Service (WCS)
Navigate to the dataset THREDDS catalog page
Click on the WCS link
GetCapabilities and DescribeCoverage
The WCS link on NCI's THREDDS catalog page will display the WCS 'GetCapabilities' request in xml, which describes a brief description of the WCS parameters (metadata, services, and data) available by the server.
GetCapabilities example:
For a more complete description, the DescribeCoverage can be requested:
GetCapabilities example:
GetCoverage
Similar to WMS, the information displayed by the WCS GetCapabilities and DescribeCoverage can be used to generate a GetCoverage, which is an operation where the server generates a coverage of a specified variable/layer in a specified format (GeoTIFF or NetCDF3).
GetCoverage parameters:
| Parameter | Required/Optional | Input |
|---|---|---|
| service | Required | WCS |
| version | Required | 1.0.0 |
| request | Required | GetCoverage |
| coverage | Required | <variable> |
| format | Required | GeoTIFF , GeoTIFF_Float , NetCDF3 |
| bbox | Required | <ymin,xmin,ymax,xmax> |
| srs, or crs | Required | <srs_value> or <crs_value> |
| time | Optional | <time_value> |
