Power BI: Creating a TopoJSON file of Australian postcodes for use with Shape Map

Power BI: Creating a TopoJSON file of Australian postcodes for use with Shape Map

In a recent consulting project, I needed to plot analytic values over postcodes. I couldn’t just do it with the built-in maps control, mostly because the system that we’re developing on doesn’t have Internet connectivity. I was keen to upload the mapping data directly into the report, and the Shape Map control (while still in preview) seemed to fit what I needed exactly.

However, when you load custom maps into the control, they need to be in TopoJSON format. Now TopoJSON is a specific extension over GeoJSON which has been pretty common for a while. I tried just using a GeoJSON file with the control, to no luck.

What was successful was to download the postcode shapes from abs.gov.au under AUSSTATS.

I downloaded the 2011 shape file for Australian postcode areas.

Next I used the  website at https://mapshaper.org/ to do the following:

  • Loaded the shape file
  • Simplified the shape file (I reduced it to about 2% of the original size, while opting to keep any small areas)
  • Export the data as a TopoJSON file
  • (Optional) I then edited the TopoJSON file to rename my postcode column from POA_CODE to Postcode and from POA_NAME to PostcodeName.

What an awesome site mapshaper.org is !

Notes on Shape Map

To use the shape map control, you need to do this:

  • Make sure you have the Shape Map control (it’s currently a preview feature that needs to be enabled)
  • Drag the column containing the postcode to the Location field.
  • Once you’ve done that, on the format page, you can choose to add a custom map. I imported my TopoJSON postcodes file
  • Drag the analytic value to the Color saturation field.
  • Set the background color and border color.

When I first did this, nothing worked for me. Eventually I worked out that my source data had integer postcodes but the ones in the file were just text fields. I added a computed column to my data, made sure I had text postcodes available, and used that column, then all was good.

I hope this helps someone.

2019-11-05