Sabtu, 12 April 2008

Accessing GeoBase Web Services

GeoBase, the Canadian government portal for free geospatial data, has made several GeoBase layers available as OGC-compliant WMS'. It is also worth noting that the data is free from most restrictions, as stated in the license agreement.

One of the new features in ERDAS IMAGINE 9.2 is the GeoServices Explorer. It is a new way to access web mapping services from desktop versions of IMAGINE and LPS.

Once you login to GeoBase, accessing their WMS layers is pretty straightforward. They send you the WMS service URL in an email, and that's all there is to it... In IMAGINE it is fairly simple to connect - just open a viewer, hit the "open layer" icon, choose a Web Mapping Service in the file type, and then hit the "Connect" button on the bottom right hand side of the interface.

After you hit the "Connect" button the GeoServices Explorer will open (see below). This will list all the WMS layers you can connect to once you have added the GeoBase services. There is a huge wealth of information available in GeoBase. The only thing I couldn't find that I had been hoping for was the SPOT 4/5 data that was made available for download earlier this year. I was able to download the SPOT data but unfortunately just didn't see it as an available layer to connect to...
In the example below I connected to the Canada-wide AVHRR composite - which was a breeze to connect to and display. It was also easy to display other layers such as roads and cities. They also have several layers outside Canada, covering the US, parts of Africa, and a few global datasets. I've included a screen capture of the IMAGINE viewer with the AVHRR data loaded in it.

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