Recreating historic maps: interview with Christopher Wesson

Last week we celebrated our 225th anniversary and shared with you two new maps created by our Cartographic Design team. Chris and Charley took inspiration from map styles in our history and used current OS data to recreate the look and feel. Chris chose early 19th century OS maps and decided to recreate the urban environment of London. We catch up with him to find out how he went about the challenge.

Chris' London map

Chris’ London map

Tell us about the map era that you chose

I’d already decided that I’d like to concentrate on an urban map and chose London as it was one of the earliest cities to appear on OS maps. I looked at the first OS map from 1801, showing the county of Kent, and parts of London and realised that I’d need to look at other maps too in order to be able to replicate all of the features needed to show our current data. London was first mapped in the four county maps in the ‘Old Series’, the first of the OS one-inch map series’. I decided to take the earliest OS cartographic representations I could find for that scale for each feature used on the map, so it is a hybrid of maps from the 19th century as opposed to a direct copy of the 1801 Kent map style.

Did you use 2016 cartographic techniques to create the maps?

I tried to use modern-day carto techniques, so as much was automated as possible, but to capture the original styling, some hands-on work was needed. For example, I created tree symbols and vegetation in two ways. Some were made with ESRI’s cartographic representations using existing symbols, but I made other symbols and their patterns by tracing and scanning from the original map to create a digital file and then used a GIS to complete the work.

Modern-day London covers a huge area, how did you decide the extent of your map?

The extent of the map was decided by the production size of a Custom Made map, so that we could easily print it! I wanted to show as much of London within that as possible, especially out to Richmond in the west and City Airport in the east. To achieve this, I centred the map on the Houses of Parliament. Interesting fact – it’s not labelled as Houses of Parliament on the map as there was insufficient room so I used a description, rather than ‘Parliament’ I chose its original description of  ‘Palace’ based on the building’s actual name, ‘Palace of Westminster’.

Chris used current OS data to recreate a 19th century style map

The map was centred on the Houses of Parliament

And how did you decide what features to include in the map?

The challenge was in creating a mid-scale map, but the level of detail in there is actually more similar to a local level map. The original map was a 1:63,360 map (one inch to the mile) but with a level of detail more commonly associated today with local level of map such as 1:10,000 scale. As there were fewer features on our landscape and less urban sprawl at the time, so the product specification could at that time show more – such as field boundaries and all churches. I tried to match the generalisation on the map and replicate the level of detail, but we have and capture so many more geographic features per unit area today that the map has been produced to two inches to the mile and not one inch to the mile.

I’ve kept the lettering, marginalia, title and scale bar as similar to the original as possible. I also tried to include as many historic specification features as possible – churches, hospitals, railway stations and windmills (did you know there are windmills on the London map today? Have a look at Wimbledon Common…). Alongside the traditionally-shown features, I’ve added symbols that would be popular now, such as museums, universities and some tourist features, even the Emirates Air Line cable car across the Thames. I’m really trying to combine the best of the old and new and bring those two worlds together.


How did you create the map?

The original maps from the era were in the Cassini projection, as it was before British National Grid existed, so I had to set ArcGIS to that coordinate system. In fact, the large majority of my efforts, around 80%, were in heavy processing and regeneralisation to get the detailed, current data looking like the old map. It was at least a 16-step process to create buildings alone and I used spatial toolsets such as FME far more than usual to manipulate the data. This was partly due to generalising data from scratch and partly because some things were created completely new – such as having to define all of the parks. Compare this to cartographers in the past and their efforts would have been focused on hand-drawing but like me would have often had a defined template to follow.

I used a wide range of OS products and databases in the replication, from our most detailed base data through to our mid-scale open data product OS VectorMap District. I even tried using the black detail from 1:25,000 Scale Colour Raster for some of the features, but it didn’t look quite right in keeping with the original map and besides, it felt like cheating.


One area that needed sizable consideration was railways and I had to look to OS maps from outside London to find these and then recreated that style within my map. You see in London railways were later added but in a very bold style that looked out of place when I took it back to the early 19th century.

The only use of colour on the map is for main roads, as with the old 1801 map, the rest is shown in shades of grey and black.

So roads and railways are included, could you navigate with this new map?

It’s actually highlighted how much map style affects how you read a map. The colours and styles are very different from modern OS maps and I found it hard to track and compare places between the two maps when I was working on it.

What was your favourite part to work on?

I really enjoyed, although it was very time consuming, setting the place names in position. I did this manually and printed out the map without any names and then compared current and historic data to decide where to place names. A current day challenge, particularly for London, is the fact geographic and administrative place names are now shown – so I decided to only work with the geographic place names. Settlement names generally refer to far smaller areas on the historic maps as the large suburban areas of today were often only villages with one or two streets in the early 19th century.


Which resources did you use?

I mainly used ArcGIS, FME and Photoshop for the processing and map creation, also 1Generalise to check and tidy the buildings. Illustrator was used for the marginalia. The size of the map and the detail within it mean that for some features I needed to upgrade my GIS installation from ArcMap to ArcGIS Pro to make use of the improved processing and rendering power. I had to extract it layer by layer and the build layers back up in Photoshop, and even in raster on a powerful machine data volumes were still troublesome.

For research in historic OS maps, the NLS archive was excellent, especially for helping me with the name placement. I also used mapco.net and the book ‘London in maps: a changing perspective’.

Lastly, tell us an interesting fact about the map…

The scale bar is described as a ‘scale of two hands’ – the imperial length of the bar itself. In the earliest maps, the title of the scale bar was in reference to the physical length of the bar on the piece of paper. It later switched to the ‘map scale’, for example ‘one inch to the mile’, etc. Two hands was roughly equal to a link on the old surveyors’ measuring chain.

Buy Chris’ map in our Map Shop – just £12.99

We’ll be bringing you an interview with Charley Glynn, creator of our second 225 map, next week.



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