The Wrong Side of my Car
The blog that wants to go obsolete
The scale on maps is… quite fluid
Remember when the map was still this huge folded sheet of paper in the door of your car?
By now, that has become yet another thing inside your phone, just like your FM radio, your flashlight, MP3 player, agenda, alarm clock, newspaper. Maybe not that FM radio anymore, but you get the idea.
Even though that old paper map and this map inside your phone come from the same reality, they are not quite the same. Below is a modern slippy map (I picked OpenTopoMap, based on OpenStreetMap data *1) and the stuff that used to be printed on the Michelin paper maps.
Can you spot the differences?
Around the turn of the century, we got maps on our Personal Computers at home. First as applications installed from CD-ROMs. You could then move through the map interactively in all its late 1990’s pixellated glory. Thanks to broadband internet online maps soon followed. For example, Mappy, or ViaMichelin. Powered by Macromedia® Flash™. Google Maps came online a bit later, in 2005.
If the name ViaMichelin sounds familiar, yes, it is that Michelin, the one you almost certainly saw on a few paper maps if you grew up in Europe. And on those Formula 1 tyres. And what is more, If you look around a bit on ViaMichelin, you may find the map images from those paper maps *2. That is where the right half of the image above comes from.
Getting the most out of your paper
Paper, unlike that slippy map on your phone, has a finite size. And also a very limited amount of zoom levels. *3 So, you want plenty of detail on it? Cover a large area? And keep the size of that sheet manageable? Pick two.
And that compromise is why those differences exist.
Pay attention to how villages are represented on both maps. The Michelin half is on a smaller scale. But look for some villages. Can you find Rillaar or Lubbeek? They seem… larger?
Let’s zoom in a bit:
Note that you can drive around the church in Lubbeek. If we zoom back out that detail becomes too small to be visible at that scale:
And yet, the Michelin map, although at a similar scale, shows this detail:
If we draw the centrelines of the map symbols from the Michelin map onto the OpenTopoMap map, you can see how different geometry is that gets drawn on the map.
I am also not sure why Michelin has chosen to include this detail, but curating which streets to show is something else they almost certainly did.
The difference in shape is easily visible with some towns.
This may look weird, but if you think about it, it doesn’t matter much if you are finding your way. A right turn is still a right turn. Following the n223 on the map towards the north still means following that road to the north in real life. The distortion is a low price to pay for having much clearer detail at this map scale than you would otherwise get *4.
There is also the problem of things overlapping on the map. Map symbols have a certain size, and if you zoom out a bit, these sizes are much larger than the scaled down version of the real thing. A road line 1 mm wide at 1:100,000 scale corresponds to 100 metres of width! So, what happens if you have, say, a railway right next to a road? These are almost certainly less than 100 m apart, so on your map the symbols will end up overlapping. So, the map makers will add some separation so you can still see both lines, with some space in between so the map can show things like underpasses.
The larger picture
I tried to line up the two maps, which was… interesting. I am not sure what projection the Michelin map uses — it was displayed on a slippy map and slippy maps use Mercator projection, but the paper maps almost certainly do not use that projection. So I don’t know how they lined it up with their Tomtom layers.
But secondly I think this slight tweaking of layouts to improve clarity also happens on larger scales. Compare for instance the E314, the motorway going northeast from Leuven. Again, for finding your way, this is completely fine.
Whereas if you compare OpenTopoMap zoom levels, you will notice the features line up exactly. (this seems to be the norm on all other modern slippy maps as well.)
It is one of these neat things that goes into making maps. It is subtle — you may very well never notice this unless you read something about it. While still making a map substantially more useful.
OpenStreetMap provides not only the map images, but also the underlying map data. You are free to create your own map styles and render your own tile layers with those styles.
OpenTopoMap is one such style, based on German topographic maps. On the about page you can spot the mention of displacing features so they don’t overlap, as a possible topic for someone’s Master’s thesis.
Or maybe not anymore, who knows when this will get removed.
Pay attention to the copyright notice at the bottom. The map image you initially see seems to come from Tomtom data — a name you may recognise from back in the day when a GPS navigation device was still something you bought for in your car.
There used to be a "Michelin Map" button. This would create a popup with another map, and if you were alive before everyone used smartphones you’ll almost immediately recognise the symbology used on paper Michelin maps, like the red/yellow motorway lines, or if you zoom out a bit, the yellow blobs used to show urban agglomerations on 1:1,000,000 scale maps.
This amount is almost always 1 for topographic maps, but for road maps you often also get zoomed in versions of cities, and sometimes a zoomed out overview of the entire covered area. Anyway, it is much more limited than what we now have on our software maps.
Did you ever see the Tabula Peutingeriana? This is a schematic map of the Roman Empire, and it has to fit the extreme aspect ratio of a scroll.
Harry Beck’s iconic map of the London Underground shows another well known trade-off. Or is a map like that of New York better?
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