In reply to Sam.
Sam, thank you for sharing this. The map you produce looks impressive!

However, I thought that if 20,000,000 is way too many for a browser, it may be too many for users as well. While looking extraordinary, the problem with this map is that it shows too much information at the same time. Thus, usability of it suffers. The areas are so small and there are so many of them that users cannot just select what they need or want with a single click. They would need to zoom in first in order to be able to see clearly what they click on. But there is little information on where to zoom in.

I believe that usability of this application can be considerably improved by applying a “divide and conquer” multilayer approach. What if instead of cramming all your small regions into a single map, you display only countries (Scotland, Wales, England, Ireland, ...) first. When user clicks on a country, you show another map with that country only and regions in that country. And finally, when user clicks on a region of the country you show Local/unitary authority.

Such design will facilitate users’ navigation and also split your HTML into smaller, manageable pieces. In essence, that will implement a drill-down approach, which provides navigation through a hierarchy of regions. If you are interested, I am planning to develop a SAS code sample and publish a blog post detailing this drill-down approach. Stay tuned.