Retrieving coverage data

The following shows how to extract coverages.

Retrieving the full coverage

The following request retrieves usa fully, at its native resolution, in its native CRS and format:

http://localhost:8083/geoserver/ows?service=WCS&version=2.0.0&request=GetCoverage&coverageId=usa

Element

Description

http://localhost:8083/geoserver/ows

The base URL

service=WCS

The service

version=2.0.0

The service version

request=GetCoverage

The request

coverageId=usa

The coverage that should be returned (just one)

Browsers often do not open the file directly, but any image viewer will.

Retrieving the full coverage in a different format

This request returns the same coverage, but as a PNG (thus, non geo-referenced):

http://localhost:8083/geoserver/ows?service=WCS&version=2.0.0&request=GetCoverage&coverageId=usa&format=image/png
../_images/full.png

The full result as a PNG

The new parameter here is the format one:

Element

Description

format=image/png

The output format (one of those listed in the capabilities documents)

Getting a subset of the data

Selecting a spatial subset of the data is called trimming in WCS and it’s controlled by subset parameter. Coverages can be N dimensional, so a subset range needs to be specified for each axis (in this case, only Lat and Lon). The following request extracts part of California:

http://localhost:8083/geoserver/ows?service=WCS&version=2.0.0&request=GetCoverage&coverageId=usa&format=image/png&subset=Lat(30,42)&subset=Long(-125,-115)

Element

Description

subset=Lat(30,42)

Latitude range to be extracted

subset=Long(-125,-115)

Longitue range to be extracted
../_images/trimming.png

A subset of the coverage, as a PNG

Getting a scaled down version of the data

Sometimes one needs the whole area, but the provided resolution is too high for the needs at hand, and the download can be reduced by usin a lower resolution. A simple way to achieve that is to use the scalefactor parameter, which multiplies the output size accordingly:

http://localhost:8083/geoserver/ows?service=WCS&version=2.0.0&request=GetCoverage&coverageId=usa&format=image/png&scalefactor=0.25

Element

Description

scalefactor=0.5

Scaling factor for the output image
../_images/scalingByFactor.png

A scaled down version of the coverage, as a PNG

Getting specific bands

With the popularity of multiband sensor imagery from satellites (e.g., Landsat, Sentinel) it can be useful to only download the bands one is interested into. The following request adds a rangesubset parameter to only extract the red band of the layer:

http://localhost:8083/geoserver/ows?service=WCS&version=2.0.0&request=GetCoverage&coverageId=usa&format=image/png&rangesubset=RED_BAND

Element

Description

rangesubset=Red band

Comma separated list of band names to be extracted
../_images/red_band_only.png

A subset of the coverage, as a PNG

Downloading the data in a different projection

Sometimes the downloaded data needs to be integrated with other local data. It can be convenient to have it already in a common Coordinate Reference System. The outputCRS parameter can be used to reproject the coverage, in the following example:

http://localhost:8083/geoserver/ows?service=WCS&version=2.0.0&request=GetCoverage&coverageId=usa&format=image/png&outputCRS=http://www.opengis.net/def/crs/EPSG/0/2797

Element

Description

outputCRS=http://www.opengis.net/def/crs/EPSG/0/2797

The output CRS, in this case, a Lambert designed for Kansas
../_images/reprojected.png

A subset of the coverage, as a PNG