...
This procedure works for all subsequent <keyword,value> pairs in this primer:
| Code Block |
|---|
http://geoport.whoi.edu/thredds/wms/bathy/srtm30plus_v6?service=WMS&request=GetCapabilities
|
...
Look at what versions of WMS the server has to offer (check whether the ice cream is fresh). For each version there is a
tag WCS_Capabilities with attribute version, as shown in the reduced xml file example below:
| Code Block |
|---|
<WMS_Capabilities version="1.3.0" ... >
<Capability>
<Request>
...
<GetMap>
<Format>image/jpeg</Format>
<Format>image/png</Format>
<Format>application/vnd.google-earth.kmz</Format>
<Format>image/gif</Format>
...
</GetMap>
...
</WMS_Capabilities>
|
For each WMS version a number of datasets is hosted. Select one dataset (ice cream flavour) from the list through the Layer tag. The name of the dataset is the name tag, in this case there is only topo. The xml file indicates that this dataset can be delivered in four well-known image different formats (this ice cream flavour ice cream is available in a cup, a cone and on a stick): jpg, png, kmz ad gif.
| Code Block |
|---|
<Layer>
...
<CRS>EPSG:4326</CRS>
<CRS>CRS:84</CRS>
<CRS>EPSG:41001</CRS>
<CRS>EPSG:3857</CRS>
<CRS>EPSG:27700</CRS>
<CRS>EPSG:3408</CRS>
<CRS>EPSG:3409</CRS>
<CRS>EPSG:32661</CRS>
<CRS>EPSG:32761</CRS>
...
<Layer>
<Title>UCSD SRTM30_v6 Global DEM (30 sec)</Title>
<Layer queryable="1">
<Name>topo</Name>
...
<Style><Name>boxfill/redblue </Name>...
<Style><Name>boxfill/redblue </Name>...
<Style><Name>boxfill/alg </Name>...
<Style><Name>boxfill/ncview </Name>...
<Style><Name>boxfill/greyscale </Name>...
<Style><Name>boxfill/alg2 </Name>...
<Style><Name>boxfill/occam </Name>...
<Style><Name>boxfill/rainbow </Name>...
<Style><Name>boxfill/sst_36 </Name>...
<Style><Name>boxfill/ferret </Name>...
<Style><Name>boxfill/occam_pastel-30</Name>
...
</Layer>
</Layer>
</Layer>
|
...
keyword | value | source |
|---|---|---|
service | WMS | Mandatory WMS standard value |
request | GetMap | Mandatory WMS standard value |
version | 1.3.0 | One of the mandatory WMS standard values returned by returned by the |
BBOX | 0,50,10,55 | bounding box: min(longitude),min(latitude),max(longitude),max(latitude) . WMS is know to be a hotchpotch for coordinate order, this particular server configuration seems to prefer lat-lon. |
layers | topo | WMS counterpart of WCS |
format | image/png | One of the mandatory WMS standard values by returned by the |
CRS | EPSG%3A4326 | One of the server-defined values by returned by the |
SRS | EPSG%3A4326 | for WMS version 1.1.1 use SRS instead of same as CRS, and mind that lat-lon have been swapped for WGS84 EPSG%3A4326 compared to version 1.3.0 |
width | 800 | width of the image in number of pixels. The xml file show a max |
height | 600 | height of the image in number of pixels |
styles | boxfill/redblue | One of the server-defined values by returned by the |
A valid WMS request example for one of the available formats is given below (NB you can copy-n-paste it into your browser address without removing the end-of-line enters). You can copy it into your browser to obtain the image, and see that it works. We chose the same bounding boxes as in the OPeNDAP primer that access these very same datasets via netCDF libraries in Matlab, python or R. We discussed the pros and cons of WCS vs OPeNDAP in a paper in Transactions in GIS that was presented at the FOSS4G conference.
| Code Block |
|---|
http://geoport.whoi.edu/thredds/wms/bathy/smith_sandwell_v11?service=WMS
&version=1.3.0
&request=GetMap
&bbox=50,0,55,10
&layers=topo
&format=image/png
&crs=EPSG%3A4326
&width=800
&height=600
&styles=boxfill/redblue
|
...
Some additional, optional WMS keywords are also possible. In addition, some WMS implementations offers more functionality than described in this primer. It it also possible to request a legend for a specific style, and to request the data at one pixel an image you requested. For these more sophisticated options, please refer to the full WMS specifications or WMS extentions with some non-standard extensions by THREDDS/ncWMS. An import ones one is COLORSCALERANGE.
keyword | value | source | |
|---|---|---|---|
TRANSPARENT | True | Background transparency of map, valid for encoding format that can handle transparency, e.g. png. | standard |
time | yyyy-mm-ddTHH:MM:SSZ | ISO time notation. Only when data are time-dependent. When not specified for data that is time-depended, the latest time is returned. Time is not implemented in most GIS-minded software packages yet. For an example on how to specify time requests see MapServer . For an example of time implementation see the ADAGUC WMS server and WMS web client. | standard |
elevation | number | elevation of layer desired | standard |
BGCOLOR |
| background color of map (format 0x hexadecimal code of color, so white is &BGCOLOR=0xffffff) | standard |
COLORSCALERANGE | "auto" or "min,max" | min. and maximum color range values | NOT STANDARD |
...
See also: MassGIS WMS, Opengeo WMS, NLR geo services
Examples
| Gallery |
|---|