Monday, January 31, 2011

Airports, Part 2

In my first installment of the airport series I presented some basic mapping techniques I used while mapping rural airports in Kansas. One comment I got on IRC suggested using a slightly different tagging scheme for displaced thresholds. The suggestion (I believe it was from pnorman) was to tag it with two tags. One being aeroway=runway and the other being runway=displaced_threshold. While I haven't gone back and changed my previous work, this may be a better way of doing it. First of all, they would get rendered on the default map. I know, I know... "don't tag for the renderer!" But here's the thing: This is technically not incorrect. Displaced thresholds are considered part of the runway and are included when the runway length is specified. So tagging it as a runway but then specifying that it is a specific type of runway is not incorrect tagging. On standard maps it would be rendered as part of the runway but someone making an aeronautical themed map could use the runway=displaced_threshold tag to differentiate it and produce a customized rendering.

Before I go on, I am just going to repost a link to the OSM wiki page for Airports as a reference.

Now on to some new material. I was moving west-to-east through Kansas so the first "big deal" airport I came to was the Salina Municipal Airport. Its 17/35 runway is a massive 12,300 feet (3.8 kilometers) long. Any aircraft currently in service could land here with room to spare. Why does a municipal airport in a city of under 50,000 people in the middle of Kansas have such a massive runway? The military, of course! This facility was built at the beginning of World War II and was used to train heavy bomber crews. Then during the cold war it became part of Strategic Air Command operations until it was closed and turned over to the city of Salina in 1965. (source: wikipedia) Now it serves mostly general aviation but is also used by Kansas State University's aviation program which is based at the Salina campus. A few years ago it was used by Steve Fossett as the start and end point of his solo, nonstop flight around the globe. And I got to bill them for the telecommunications services they used while doing it! (My current day job deals a lot with the telecom billing system at KSU)

I promise, I'll get to the mapping in this post, eventually. But I should point out that this is one thing I love about contributing to OSM. Seeing something unusual in aerial imagery can often lead to an hour spent on wikipedia or a fun discussion on IRC involving people from around the world or, occasionally, a field trip to go see what the heck is happening "on the ground" to cause it to show up a certain way in aerial imagery.

Friday, January 7, 2011

Airports, Part 1

For the past few days I've gone on an airport binge in OpenStreetMap. I ended up learning a lot about airports. It was fun to start mapping, then come across something different or notice a new detail and realizing that this too can be mapped! Here are my musings on the subject. Feel free to tell me I did it all wrong in the comments :)

The recent import of airport nodes from and the subsequent discussion sparked the idea to map easily identifiable runways from aerial imagery. So I downloaded all "aeroway=aerodrome" nodes within Kansas from the XAPI. In addition to the above mentioned import, a lot of airports were imported from USGS GNIS (Geographic Names Information System) back in early 2009. In total there were just under 600.

This being Kansas, a vast majority of those 600 "airports" are nothing more than a flat spot in a field where farmer Joe lands his crop duster. They have such names as "Lundgren Hereford Ranch Airport" or "Flying N Ranch Airport." They should probably be downgraded from "aerodrome" to something else and not rendered at zoom level 10 like they are now. Right now looking at western Kansas at z10 reveals a ridiculous number of airports being rendered. I have yet to see any consensus on a tagging scheme for smaller airports so I mostly just ignored them. Additionally, the aerial imagery I was using (USGS NAIP) wasn't really good enough to reliably pinpoint these grass strips in the middle green fields. It also didn't help that the GNIS information is often off by quite a bit so I wasn't sure if the runway was just blending in or if there really wasn't one in the field I was looking at but rather 2 fields over.

The more interesting airports are the municipal air fields. Most of these have a paved runway, sometimes in addition to a grass one. Even small airports stick out when they have a paved runway: