[Stratoscope]

Good point. This may be a case where domain knowledge is helpful.

One of the reasons they brought me in on this project is that besides knowing how to wrangle data, I'm also an experienced pilot. So I had a good intuitive sense of the meaning and purpose of the data.

The part of the data that was identical is the description of the airspace boundaries. Pilots will recognize this as the famous "upside down wedding cake". But it's not just simple circles like a wedding cake. There are all kinds of cutouts and special cases.

Stuff like "From point A, draw an arc to point B with its center at point C. Then track the centerline of the San Seriffe River using the following list of points. Finally, from point D draw a straight line back to point A."

The FAA would be very reluctant to change this, for at least two reasons:

1. Who will provide us the budget to make these changes?

2. Who will take the heat when we break every client of this data?

[ebolyen]

I see, so it's a procedural language that is well understood by those who fly (not just some semi-structured data or ontology). This is a great example of the advantage of domain experience. Thanks for sharing!

[Stratoscope]

> a procedural language that is well understood by those who fly

That is a great way to describe it!

Of course it is all just rows in a CSV file, but yes, it is a set of instructions for how to generate a map.

In fact the pilot's maps were being drawn long before the computer era. Apparently the first FAA sectional chart was published in 1930! So the data format was derived from what must have been human-readable descriptions of what to plot on the map using a compass and straightedge.

I just remembered a quirk of the Australian airspace data. Sometimes they want you to draw a direct line from point F to point G, but there were two different kinds of straight lines. They may ask for a great circle, a straight path on the surface of the Earth. Or a rhumb line, which looks straight on a Mercator projection but is a curved path on the Earth.

You would often have some of each in the very same boundary description!

For anyone curious about this stuff, I recommend a visit to your local municipal airport and stop by the pilot shop to buy a sectional chart of your area.

[tass]

Paper charts are great (they're fairly cheap and printed quite nicely in the USA at least) but you can get a good look at these boundaries through online charts.

https://skyvector.com is a good way to view these.

[Stratoscope]

Thank you! I was trying to remember the name of that site and it slipped my mind. Yes, SkyVector is great.

[hamasho]

I think if you know the domain well, it's not "premature" at all.