GeoTrellis 0.8.1 is out, and with it is a new way to view your Raster data in an easy an informative way. In this blog post, we’ll take a look at some Pennsylvania elevation data using the new GeoTrellis admin tool.
Starting the admin tool
If we run the server (see the tutorial or the README on the github page for the code for how to run the server), we can go to http://localhost:8880/admin/ and get to the admin site:
In this case, the admin site is showing data from a catalog that I have locally. The catalog’s name is “Catalog of Rob’s Data”, and it has a number of data stores (indicated by the folders on the left). The catalog that the admin site displays is the one set in the configuration as geotrellis.catalog. For more information about the GeoTrellis catalog, see the overview section on the subject in the documentation.
We can open up the ‘NED data’ data store and select Philadelphia to visualize the raster:
The raster fits over the base map perfectly. This is because both the base layer and the raster have a projection of Web Mercator (ESPG:3857); if the raster was not in that projection, it would be places in an incorrect spot on the map (although you would still be able to view it).
Changing the base layer
We can choose another base layer using the Leaflet layer chooser on the right side of the map:
Let’s change it to the Stamen Toner layer, and increase the opacity of the raster using the Opacity slider, in order to get a more clear view of the coloring:
Changing the Color Ramp
Seeing Raster Values
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