[CrimsonCape]

C dev: "You are telling me that the three digit codes are not globally unique??? And now we have to add more bits to the struct?? That's going to kill our perfectly optimized bit layout in memory! F***! This whole app is going to sh**"

[throw0101a]

> C dev: "You are telling me that the three digit codes are not globally unique???

They are understood not to be. They are generally known to be regionally unique.

The "DVL" code is unique with-in FAA/Transport Canada control, and the "DVL" is unique with-in EASA space.

There are pre-defined three-letter codes:

* https://en.wikipedia.org/wiki/IATA_airport_code

And pre-defined four-letter codes:

* https://en.wikipedia.org/wiki/ICAO_airport_code

There are also five-letter names for major route points:

* https://data.icao.int/icads/Product/View/98

* https://ruk.ca/content/icao-icard-and-5lnc-how-those-5-lette...

If there are duplicates there is a resolution process:

* https://www.icao.int/WACAF/Documents/Meetings/2014/ICARD/ICA...

[skissane]

> They are understood not to be. They are generally known to be regionally unique.

Then why aren’t they namespaced? Attach to each code its issuing authority, so it is obvious to the code that DVL@FAA and DVL@EASA are two different things?

Maybe for backward compatibility/ human factors reasons, the code needs to be displayed without the namespace to pilots and air traffic controllers, but it should be a field in the data formats.

[rounce]

Given airport codes are namespaced by ICAO, it seems a bit of an oversight that the same scheme hasn’t been extended to other infrastructure like VORs and waypoints for systems exactly like this one, for cases when uniqueness is required.

[throw0101a]

> […] like VORs and waypoints for systems exactly like this one, for cases when uniqueness is required.

AIUI, most VORs (and in the past, NDBs) are located at airports. And there is an airport at Deauville (DOL/LFRG):

* https://en.wikipedia.org/wiki/Deauville–Normandie_Airport

But the beacon is elsewhere, apparently in some random(?) field:

* https://www.google.com/maps/place/49°18'38.0%22N+0°18'45.0%2...

* https://opennav.com/navaid/FR/DVL/DEAUVILLE+SAINT+GATIEN

[rounce]

There are plenty of navaids that aren’t associated with an airport, there’s probably around a dozen like this just south-east England.

[Moru]

Some history/explanation [1]

[1] https://news.ycombinator.com/item?id=33948915

[CrimsonCape]

It seems like tasking a software engineer to figure this out when the industry at large hasn't figured this out just isn't fair.

Best I can see (using Rust) is a hashmap on UTF-8 string keys and every code in existence gets inserted into the hash map with an enum struct based on the code type. So you are forced to switch over each enum case and handle each case no matter what region code type.

It becomes apparent that the problem must be handled with app logic earlier in the system; to query a database of codes, you must also know which code and "what type" of code it is. Users are going to want to give the code only, so there's some interesting mis-direction introduced; the system has to somehow fuzzy match the best code for the itinerary. Correct me if i'm wrong, but the above seems like a mandatory step in solving the problem which would have caught the exception.

I echo other comments that say that there's probably 60% more work involved than your manager realizes.

[marcosdumay]

Hum... Somebody has a list of foreign local-codes sharing the same space as the local ones?

I assumed IATA messed up, not I'm wondering how that even happens. It's not even easy to discover the local codes of remote aviation authorities.

[skissane]

> I assumed IATA messed up,

This isn’t IATA. IATA manages codes used for passenger and cargo bookings, which are distinct from the codes used by pilots and air traffic control we are talking about here-ultimately overseen by ICAO. These codes include a lot of stuff which is irrelevant to passengers/freight, such as navigation waypoints, military airbases (which normally would never accept a civilian flight, but still could be used for an emergency landing-plus civilian and military ATC coordinate with each other to avoid conflicts)

[marcosdumay]

Hum, no. It's not about ICAO codes. It's about local UK codes, and IATA ones used by mistake.

[skissane]

The code that caused the issue is DVL, which isn’t a “local UK code”, it is a code used by the FAA for a location in the US and a code used by EASA for a location in France. And I didn’t say ICAO issued the codes, I said the process of issuing them by regional/national aviation authorities is “ultimately overseen by ICAO”, which I believe is correct.