30 Days of Maps Day 3 - Polygons

Any now we're moving along to day 3 of the #30DayMapChallenge.

The theme for today's map is polygons - A map with polygons. Regions, countries, lakes—this day is for defined shapes that fill space..

Whilst Icon Map Pro has a wide range of options for displaying polygons - the most popular and fastest way is to upload a file into the report, whether it's Esri Shapefile, KML, GeoJSON or TopoJSON. However, the downside of this, is that it increases the size of the report, and for really large files, this approach won't work. For example in today's challenge, I'm using the National Forest Inventory from the Forestry Commission's Open Data site. This dataset is downloadable as an Esri Shapefile, but it's nearly 2gb in size containing more than 650,000 polygons. For large and complex datasets such as these, we need a different approach. I've decided to use vector tiles, to break up the shape file into a grid in which each square is downloaded only when required. I'm hosting my tile layer in my GeoServer, although Mapbox would also have been another easy option.

The vector tiles are then matched to my Power BI dataset on the fly, and coloured using Power BI's conditional formatting. This also means that the shapes are interactive - I can add tooltips, select them to interact with other report elements - in my case a table.

I've also included a Local Authority slicer so you can view a the woodland within a specific Local Authority area. I've added a reference layer to show the Local Authority boundaries - this is filtered by conditional formatting in Icon Map Pro to just show the boundary for the Local Authority we've filtered to.

If you'd like to see how the report was built, you can download it here.