Creating bespoke mapping from traditional Ordnance Survey rasters with hillshading and route and information overlays.
Ordnance Survey (OS) were approached to create a custom unofficial map for some of the athletes participating in V3K Ultra – a 55km running race across the highest mountains of North Wales, also known as the Vegan Welsh 3000s and now a part of Skyrunner® UK’s race series. This showcases and explains my initial design and proof.
I don’t often get the chance to make paper maps at work these days because so much of our workload is digital and based around the styling of geographic data. However we do have a number of jobs that come into the team, largely for corporate marketing purposes, requiring routes for walking, running or cycling events to be displayed over our traditional raster products. These raster products at scales of 1:25 000, 1:50 000 and 1:250 000 are essentially electronic, tiled versions of our OS Explorer Map, OS Landranger Map and OS Travel Map paper series’.
To be honest, I am not the biggest fan of using traditional OS raster products as a base for custom paper maps. They are already ‘complete’ maps, in many cases overcomplete, and so do not accommodate overlain detail easily – even when ‘washed out’ which is in my eyes a horrible last resort.
At work, we are often forced down this ‘traditional raster’ route either as a specific customer requirement or because we do not yet have local vector content under our Multi-Resolution Data Programme (MRDP) as we do for district level.
As a cartographic design consultant, the raster base limits what I can do creatively and limits the options for design. Unlike vector data which can be styled however one wishes and can also be generalised, one pretty much has to accept raster data as it is. There are certain things that can be done as highlighted on an earlier OS blog post but I personally would only do so as a last resort. However the flip-side is that we are extremely lucky to have such highly acclaimed products and in the case of 1:25 000 scale colour raster, an extremely detailed and accurate walking and outdoor activity product. In this regard, a lot of the work and a lot of the cartography has been done for us.
A group entering the Skyrunning V3K, also known as the Vegan Welsh 3000s, would like a bespoke map using an OS Explorer-style base to allow them quick and accurate reference to navigate a 35-mile long running route across some of the most challenging mountain terrain in North Wales.
The map needs to be printed on durable paper of suitable size for the field with the route clearly shown. It should also show topography. Map scale should be appropriate to both cover the race area and show the route clearly.
My first task was to work out the geographic area of the route. Supplied as a GPX file on the official website (as well as directly by e-mail), I used QGIS to efficiently open the GPX file. I could have created my map entirely in QGIS but as much as I think QGIS is wonderful software for creating maps, it still has a long way to go so far as paper map creation is concerned. Whilst other GIS packages fare slightly better, I quickly decided that Adobe Illustrator, a vector graphics package, would be best.
Many cartographers take GIS data into Illustrator using a plug-in called MAPublisher which I would highly recommend if you do this kind of thing regularly, however we do not and so I have become pretty accustomed to my own route of GIS to PDF to Illustrator.
So I decided to create my map ‘layers’ in QGIS and then export each out as a PDF to then place in Illustrator.
After sorting out the route, with minimal styling – most styling can wait until Illustrator, I imported a low-resolution version of the traditional OS rasters (1:25 000 Scale Colour Raster in this case) – hence why I needed to know the geographic extent. I knew I would be importing the print-quality, higher resolution raster into Illustrator later but having a low-resolution version in QGIS helped me to line everything up later on.
Next I decided that anyone running through mountains whilst trying to read a map may well appreciate the very quick and easy reference that is hillshading. Hillshading (also known as hill-shading or shaded relief) is the representation of topographic relief by using areas of light and shadow to simulate the effect of sunlight and creating a ‘3D-like’ illusion on the map – see ReliefShading.com for more information.
Using contours from the OS Terrain (height) products I used to use Esri ArcGIS to create Triangular Irregular Networks (TINs) which represent the surface morphology and illuminate/shade those to create hillshading. However I now prefer to use the gridded height version of the OS Terrain products and load and style these directly in QGIS. If you wish to merge these ascii grid files then please refer to my earlier post and tutorial on draping terrain.
To create hillshading in QGIS, from the menu bar go to Raster _ Analysis _ DEM (Terrain Models). I personally try to avoid just using a traditional northwest lighting angle because the results are pretty poor. Illuminating from a single angle only highlights certain faces of the terrain. You do need a dominant lighting direction otherwise hillshading won’t work, but I often try to capture as many as possible. Last year Patrick Kennelly of Long Island University presented his fascinating work where he proved his algorithm to create superior hillshading and I seem to recall he was taking in literally hundreds of different illuminations. I have also previously read that Google Maps used to favour illuminating from an average angle of due north, not sure if that is still the case.
Anyway, for this map I created 5 sets of hillshading. I choose to vary not just the azimuth but also the altitude of the light. I export each from QGIS as raster (e.g. as TIFF) and load them into Adobe Photoshop. In there I assign a transparency to each with the angles I want to be more dominant having greater opacity. Once I am happy with its appearance, I then apply an adjustment curve to emphasise key features and make the hillshading a lot lighter.
As this hillshading originated from QGIS and as I exported from the same view as my route, I know they will line up perfectly on import into Illustrator. Once in Illustrator I then also replace the low-resolution with the high-resolution base maps (the 1:25 000 raster).
The data sorting now done, I am then free to style the overlay of the map as I wish (or as the customer has asked) and add marginalia, legends, etc.
So here is the result of my work, the first proof that went out to the customer:
Ordnance Survey © Crown copyright 2014. All rights reserved
The final design changed to better fit the runners’ needs with practicality becoming far more critical than presentation. This was achieved by using a more compact sheet size at a slightly smaller scale, changing the route style to suit dim light conditions and moving all marker symbols, etc. out of the path of the route itself.
The result of these amendments, the second proof can be seen below. Personally I feel the original purple to dark cyan route stood out better than the pink, but these guys have spent far more time up mountains than I have so I assume the pink they requested is somehow easier to see up there in varying weather and light conditions.
Ordnance Survey © Crown copyright 2014. All rights reserved
Hope you like what I have done. As I say, I don’t usually like this map genre with the traditional OS base, but I am quite happy with this one!
‘Raster’ and ‘vector’ data explained
Most digital images you come across are raster graphics. Pictures found on the web, photos you import from your digital camera, even most tile caches of web map services are raster graphics. They are made up of a grid of pixels, commonly referred to as a bitmap. The more pixels, the greater the resolution and quality of the image. But the main point is that rasters are static and dumb. They are very hard to restyle.
Vector graphics are commonly created in graphics packages and consist of shapes called objects. It is possible to edit each object separately, for example, change the shape, colour, size and position. File sizes are often smaller and vector graphics are scalable – ie when you resize them, they do not lose quality. In cartography, the vectors we refer to are often geographic data (geodata), i.e. attributed content from which we can create our product, often using a GIS.