Rescue services — how this layer is made

What you are looking at

Each point is a rescue station — a feature tagged `emergency=lifeguard`, `emergency=mountain_rescue` or `emergency=water_rescue_station` in OpenStreetMap. 7,132 of them worldwide, which makes this the smallest layer on HueMaps. Each is drawn as a dot coloured by which service it is and sized by the footprint of the station.

Click any station to see what OpenStreetMap records about it — the body that runs it, where a mapper noted that. Where it has a Wikipedia article, a short summary is fetched live and shown in your own language; and every station links to the OpenStreetMap object it came from.

Three services, one layer

They are together because 134 water rescue stations is not a map, and because they belong together anyway: each is a voluntary or specialist service covering ground the ordinary ambulance service cannot reach, and somebody looking for one is usually interested in the others.

They are coloured apart because the three are not the same geography at all:

Lifeguard — 5,921 features, 83% of the layer. A coastline, and sometimes a lake or a lido.
Mountain rescue — 1,077 features, 15%. A mountain range: the Alps, the Carpathians, the Pyrenees, the Lake District.
Water rescue — 134 features, under 2%. A river, a canal or a large lake, usually inland.

Drawn in a single colour the layer would read as one service scattered oddly. Drawn in three it reads as what it is — three separate patterns that happen to share a map.

The densest place on this map is Los Angeles

Not the Alps, which is what we expected before measuring. The single densest view anywhere in the world holds 351 features off Santa Monica, against 265 in the Bavarian Alps and 245 on the Santa Catarina coast in Brazil.

That is not a statement about drowning risk. Los Angeles County runs a large municipal lifeguard service and its individual towers — dozens of them along a few miles of beach — have each been mapped as a separate object. Elsewhere a beach with the same or better cover is mapped as one station, or as nothing at all.

This is the layer's central caveat, and it applies everywhere on it. A dense stretch of coast means somebody mapped the towers one by one. A blank stretch means either no service, or a service recorded as a single point, or a service nobody has mapped.

Mapped, not modelled

Each station is an object a mapper drew, from survey, local knowledge or aerial imagery; nothing here is modelled or estimated, and no national register of lifeboat or mountain rescue stations has been merged in.

What counts, and what does not

Only those three exact tag values. The `emergency` key as a whole holds over three million objects in OpenStreetMap, almost all of them fire hydrants, so it is never taken as a whole.

Some things you might expect are elsewhere or absent:

lifeboat stations are usually tagged as such rather than as `water_rescue_station`, and are not on this layer;
ambulance stations and fire stations are separate layers;
a surf club that also provides lifeguards appears only where somebody has added the emergency tag alongside the club tag.

Size

Each symbol is sized by the footprint of the station, in square metres measured on the globe. Symbol area is proportional to that (radius to its square root).

These are the smallest features on the site after the windmills: among the 41% mapped as an outline the median footprint is 52 m², which is a hut. The other 59% are a bare point with no shape and are drawn at a nominal small size rather than at the minimum.

So on this layer the colour carries most of the meaning and the size very little — a lifeguard tower and a mountain rescue base are not far apart in floor area, whatever else separates them.

Only 42% carry a name, the lowest share of the six layers added alongside this one. There is not much to name about a tower on a beach.

A few mountain rescue features are whole hillsides

The largest features on this layer are three polygons in eastern Ethiopia, each covering square kilometres of ground and tagged as mountain rescue. They are almost certainly a tagging error rather than a rescue base. There are too few to filter on, and they are named here rather than quietly removed.

A picture of the present

Today's map, not a history. OpenStreetMap is edited continuously; this copy is refreshed periodically. There is no year control, and a station closed some time ago may still be mapped until a mapper updates it. Seasonal lifeguard posts are mapped whether or not anyone is on duty today.