Subtractive Map Symbology

June 2, 2015
David Medeiros

Sometimes the very data we map can get in the way of our understanding the phenomena we are visualizing.

In the case of bird sightings for the Rose-Breasted Grosbeak, the typical approach to adding points over a map might have shown us where in time and space the birds were while on their annual migration, but the result would have also obscured the terrain over which they fly.

Using a creative visualization method of subtractive rather than additive symbology in mapping observations, John Nelson of IDV Solutions found a great way to reveal rather than hide the landscape these birds travel through. Instead of adding points for observations over a detailed map background, John used a masking technique to reveal the underlying map showing us the world the birds see as they migrate while still revealing the overall patterns in the data.

See his full blog post for the details, or click the map to see the full size animation.

Migration GIS

This is also a great example of the effectiveness of a GIF for really simple dynamic (if not interactive) mapping. You don't always need D3 or CartoDB to make a compelling animated visualization!

Get help with your own visualizations!

Curious about how to create animated GIF maps or use data masking? At the Stanford Geospatial Center, we’re not just experts in geospatial data and technology, we also know design and cartography. If you need help getting your maps to work better, stop by or send us an email!

Author

David Medeiros

Geospatial Instruction & Reference Specialist