Military sites — how this layer is made

What you are looking at

Each dot is a military site. There are more than 230,000 worldwide. Colour represents what kind of site it is, and the size of a dot represents the footprint of the site. Click on any of them to see what OpenStreetMap records, such as whose forces hold it and its website. If there's a Wikipedia article, we show a short summary and a link to the full article, in your own language where possible.

Where the data comes from

Every feature here is something a mapper added at the OpenStreetMap website, from a survey, from aerial imagery or from published sources. Everything on this map is therefore already public, and none of it comes from anything restricted. We don't model or estimate anything ourselves, and we haven't merged in any defence register.

What we include

Two selections. The first is anything carrying the `military` tag, which says what the feature is. The second is anything tagged `landuse=military`, which is land set aside for armed forces, and we need it because that land usually carries no `military` tag at all. Where a feature has both, we draw it as the more specific of the two, since the specific tag says what a place is and the land use only says who holds it.

Military airfields carry `military=airfield` and also appear on the airports layer, which is deliberate. An airfield is genuinely both, and you should find it whether you come to it from aviation or from defence.

Colour

Colour represents the kind of site. Bunkers are nearly half the layer. Land held by armed forces with nothing more specific recorded is a little under a third. The rest are barracks and bases, training areas and ranges, recruitment and administrative offices, checkpoints, trenches, nuclear test sites and airfields, along with a small group tagged `military=yes` and nothing further.

Trenches drawn as lines

Most of the trenches in OpenStreetMap are drawn as lines rather than as closed shapes or points, and this map draws points and areas only, so roughly nine trenches in ten are not here. The ones you can see are the minority somebody traced as a shape. They are real, and they are not representative of what was dug, since the great trench systems of the Western Front are almost entirely lines and almost entirely absent. Linear features are a known gap across this site.

Size

The size of a dot represents the footprint of the site in square metres. Among the features that have a shape, a typical one covers about 1,500 m², roughly a large building. Nearly a third of the layer has no outline at all, and three quarters of those are bunkers, so we draw untraced features at about 140 m², the typical footprint of a traced bunker, rather than at the typical footprint of the whole layer. The largest features are ranges, danger areas and test sites recorded as administrative areas, the biggest of them tens of thousands of square kilometres, and we cap the size scale far below them.

Where the map is empty

An empty area means nobody has mapped a site there, not that a place has none. That caveat is stronger here than on most subjects, because what appears depends heavily on what people have chosen to record. The bunkers show it most. Enthusiasts have catalogued them in detail in parts of western Europe and North America and hardly at all elsewhere, so the bunker colour shows where fortifications have been written down. Military land is recorded more evenly, because it is large and visible from the air.

Up to date, mostly

OpenStreetMap is edited continuously, and we take a new copy once every one to three months. Much of what is here is historic, and some of it is a century old. A base shown here may have closed, and a bunker usually stands long after anyone stops using it.

Source and licence

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