Satellite, Bing or OSM? How to choose the best base layer for your web map
Base layers such as satellite imagery or Open Street Map are an extremely important part of any web map. You can think of a base layers as supplementary data that’s used to enhance your core data by providing the user with context and orientation. Context tells the user about relevant conditions on the ground and orientation allows them to quickly make the connection between the area they’re viewing on the map and the area it represents in the real world.
The secret to using base maps well is giving a base map that provides just enough context and just enough orientation. If the base map is too noisy it can end up drowning out your core data, rather than supplementing it, and if your base layer it’s too sparse it leaves the user feeling lost.
Let’s take a look at some examples.
A World Map
I’ll start with a map that shows the number of datasets that have been added to Mango for a particular country in 2012. The map covers the whole world and it’s very unlikely that the user will want to zoom in much further.
Example 1: This base map used here (Light) is extremely simple and a good fit in this case, it adds to our map by giving a splash of colour to the ocean areas and cleanly plugs the holes in our data (countries with no datasets uploaded).
Example 2: This base layer (Bing Hybrid) on the other hand is overpowering at this scale. The dark blue of ocean draws the users eyes away from the core data and the labels are of little value for anyone over kindergarten age they are simply extra noise that add nothing to the overall experience.
The Buildings of a Small Town
The last map covered a huge area, whilst this one covers a relatively small area in a semi-rural setting, showing building outlines on the Isle of Man. On this map the user is unlikely to zoom out much further.
Example 1: This Bing Streets base layer is great in terms of orientation, we can see the main roads around the town and also some of the street names. It’s not so great in terms of context. What are we looking at here? Is it urban? What’s on the empty areas with no streets?
Example 2: This Bing Satellite base layer answers all of the question regarding context that we were left with in example 1, but it does so at the expense of orientation. Sure we can still see the harbour and some landmarks but if the user is unfamiliar with the area that might not be much help.
Example 3: This Bing Hybrid layer gives us the best of both worlds, the street labels give us orientation and the satellite data gives us context and is clearly the best fit in this case.
Hopefully it didn’t escape your attention that Bing Hybrid was the worst option for the fist map but the best options for the second map. It just goes to show that it doesn’t pay to always use the same base layer for each map, we should look at the map in context, think about the story the map wants to tell and which base map will supplement your core data but not overpower it.