Maps and Mappers of the 2022 calendar: Tom Armitage, October

Q: Tell us about yourself:

A: Hi, I’m Tom Armitage (@MapNav_Tom on Twitter) and I have been working in GIS for 20 Years. I’m MapTiler‘s Technical Writer and I also do some GIS training and teaching at the University of Edinburgh where I am an honorary fellow. I’m an Open Source Advocate, and have spent a lot of my career teaching GIS skills in QGIS.

Q: Tell us the story behind your map (what inspired you to make it, what did you learn while making it, or any other aspects of the map or its creation you would like people to know):

A: This map originally started as my entry for “Red” in Topi Tjukanov’s #30DayMapChallenge. I was using some quirky layers of data with minimal base mapping to give different perspectives of Edinburgh. The map is therefore part of a series with water represented on the Blue map, trees on the Green map and parking restrictions on the Yellow map. This was all made possible by having great Open Data resources from Ordnance Survey, British Geological Survey and the City of Edinburgh Council. The red map was always my favourite of the series so I made some improvements and submitted it. The Listed buildings data lends itself to the firefly cartography I used, there are different levels of protection which can be used to vary the size of the points and there are low and high density areas across the city. The resulting map shows areas with high concentrations with increasingly bright intensity. All of the maps in the series were recognisable as Edinburgh, certainly to a local anyway. However, the red map highlighted areas with the oldest buildings and so it was possible to see where the city had grown and taken over what would have been individual villages in the surrounding countryside. Coupled with Edinburgh’s sometimes bloody history (look up Burke and Hare), it’s why I liked this one the best.

Q: Tell us about the tools, data, etc., you used to make the map:

A: To create this Map, I only needed QGIS, but I made extensive use of the Blend modes and Draw effects. Those of you that follow me on Twitter will know I’m a big fan of these! First I varied the point size based on the level of protection a building had, largest points for the most highly protected. I then applied an Outer Glow to the points and made this red like the points themselves. I used the Screen blend mode on the points with the map layer and also with each other. This meant that the points would brighten the backdrop and the effect would be amplified the more the points overlapped. At this point in the process I needed to decide what scale the final map was going to be, and set the DPI in the print layout. These both affect how much overlap there is between the points so it is important to fix them first before deciding on the final point size. Varying any of these values will affect how intense the brightness gets in the final map. There was a fair amount of trial and error before I got it right! Also, to make sure that this effect works, it is important that the red used wasn’t at full saturation. I used one that was a bit darker, so that there was more room for it to become intense. One final trick I used was to put in a layer of building polygons in dark grey, over the black backdrop. This is a point dataset, but it is about the buildings, so the lighter polygons and screen blend mode helped highlight these more as areas, rather than just the points. At this scale though, the points were a better call to use than creating a polygon layer… though you may notice a couple of lonely looking dots in the Firth of Forth representing the Bridges!

Producing the map was a lot of fun, but I also learned a lot about defining a proper process and procedure to follow. This has helped a lot when creating more firefly maps!