65 :: Using the Overpass to find the Abandoned

A friend of a friend inquired about which platform I would recommend for a city-wide crowdsourced map of derelict buildings. I did some research towards this today and thought I should write down my notes before I forget what seems obvious now.

It’s hard not to recommend Google for a project that has a lead that’s not technically savvy.  The effort of learning to pin Google Form results to a Map might be a stretch for some but it’s worth the learning curve, I think.  (That is, until the next version of Crowdmap is out of beta!)

Of course, it would be better to recommend OSM because data shared with it are shared with all.

It used to be that exporting data out of OpenStreetMap required downloading the entire Planet, or you had to use JSOM or QGIS or some 3rd party service. But with the Overpass API, it’s possible to run queries on OSM for your particular needs.  The query language is a bit funky, but it’s still a wonderful thing. I haven’t figured out an exact search query because to search for ‘abandoned‘ or ‘disused‘ are not keys proper but namespaces.

So, how to use the API? You can use Overpass to extract a dataset that you then can add to Tilemill. But that generates a static map. What if you want a live map? (well, as live as the API will allow you). Well, it can be done – and some of the examples are available on github.

One day, I’d like to be able to use python to extract OSM data on a regular basis (there are a number of ways to do this, of course).  But at this time, I want something dead simple. Something like this example for how to Mashup Overpass with OpenLayers, but with Leaflet instead.

I’ve forked my own POI OSM map template to hack later on. As long as I don’t abandon this project.

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