Most of the time we use OpenStreetMap (OSM) as a gazetteer; that is, a means of representing the geographical aspects of Security Force Monitor’s data.
For example, our research indicates that the Mexican army unit 105 Batallón de Infantería had a base in Frontera, Coahuila, Mexico from 24 February 2014. To geocode this data we will search OSM to find the nearest “object” to the named settlement – in this case a “node” called Frontera (ID number 215400772) – and link it to the unit as a base. Our Research Handbook contains the rules we use for doing this.
When we publish the data on WhoWasInCommand.com it will be displayed in the “Sites” section of the record for 105 Batallón de Infantería along with all the sources that evidence it:
So far we have found OSM to be a good enough gazetteer. And it’s free. And it’s open licensed. And we can fix it if we need to. So you won’t find us moaning and whinging.
However, OSM has a number of issues with accuracy, coverage and change over time so we do not use OSM as a primary source of information. Instead we use it as one of a number of sources of lead information which help us piece together the geographical footprint of a security force. It’s why, for example, we don’t place 105 Batallón de Infantería directly at Venustiano Carranza International Airport, even though this is the case on OpenStreetMap. We don’t (yet) have other sources to evidence this, but OSM gives us a useful prompt to investigate this further.
I’ll cover the pros and cons of using OSM in our research in a future blog post but for now I’d like to talk about how we OSM in the early stages of research into a security force.
OSM is a useful tool for getting an impression of a security force’s physical infrastructure: lead information about where it may have bases and facilities, and the terrain that may be reserved for use by security forces (like firing ranges, training areas, ). How do we do this?
OpenStreetMap is a database
The points, lines and polygons (“objects”) you see on OSM are described with “tags”: for example, a tag can define a line as a “road” or a shape as a “building”, and give it a name. Incredibly, on OSM there are over 70,000 different ways to describe an object, but the tag we’re interested is “landuse=military”.
OSM currently has 70,641 objects to which the tag “landuse=military” has been applied. OSM’s own documentation about this tag is here. The tag can be refined further by applying another tag called “military=[something]” – the [something] in question can be values like the below:
- military=airfield
- military=barracks
- military=bunker
- military=checkpoint
- military=training_area
There are currently over 290 additional tags used on OSM to increase the specificity about the type of military land use.
How can we use this information to aid our research? The usual need we have is for a BIG LIST that we can simply go through one by one and use as starting points for searches or to cross reference data we get from other sources. Although we can view these items on OSM we can’t get such a BIG LIST. To do this we need to use a way of accessing OSM’s data called Overpass API. This is mostly by programmers but for us patient non-programmers there is a slightly easier way to use this API – it’s called Overpass Turbo.
Using Overpass Turbo to show military land use on OSM
So, here goes. Let’s ask OSM what objects in Mexico are tagged with “landuse=military”. Head over to Overpass Turbo:
After opening that link copy the below into the input area on the left-hand side and then hit the “Run” button (top left):
// Limit the search to “Mexico”
{{geocodeArea:Mexico}}->.searchArea;
// Pull together the results that we want
(
// Ask for the objects we want, and the tags we want
way["landuse"="military"](area.searchArea);
relation["landuse"="military"](area.searchArea);
node["landuse"="military"](area.searchArea);
);
// Print out the results
out body;
>;
out skel qt;
What’s this then? Yes, it’s a map of just those objects tagged with “landuse=military”:
Exciting! You can export this into a common geographical format (like KML or geoJSON). But I said we needed a list. Let’s alter the query a bit. Try putting this into the editor:
// Get a CSV output
[out:csv(name, "tags:name:es", "tags:name:en", ::"type", ::"id", ::"lat", ::"lon";true;",")][timeout:25];
// Limit the search to “Mexico”
{{geocodeArea:Mexico}}->.searchArea;
// Pull together the results that we want
(
// Ask for the
way["landuse"="military"](area.searchArea);
relation["landuse"="military"](area.searchArea);
node["landuse"="military"](area.searchArea);
);
// Print out the results
out body;
>;
out skel qt;
Same data, but in a list that we throw into a spreadsheet to work more on:
Even the snippet above gives us some unit and facility names to research further, as well as the locations of possible facilities that perhaps someone with local knowledge has flagged as being used for military stuff.
The queries above can be altered to search within different countries or other defined areas, examine different tags (like “amenity=police”… give it a try), and export more data (such as an object’s history).
Wrapping up
- As well as being a map that we can search, OpenStreetMap is a database that can we query in depth.
- Historical and contemporary military and police locations may be identified inside OpenStreetMap using the “landuse” tag. More information about the tagging system can be found on OSM’s own TagInfo service.
- Using Overpass Turbo we can pull out that information as use it as lead information during our research. Overpass Turbo is free to use, and can output maps and lists. The Overpass query language is documented here and there are some super examples on the OSM wiki here.
I’m sure there are more elegant ways to use Overpass Turbo than my basic code, so should anyone wish to help us out I’m all ears (tom [at] securityforcemonitor.org). We’re also interested in improving the data on military and police facilities that exists in OSM, … but that’s another post.
I hope this has been a helpful read, and do comment, respond and correct as needed.
