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Spot the error?

But Gon is as arbitrary as degrees.

Well, they used 1/10.000.000 of a quadrant when defining metre. There is no going back. SI is certainly not perfect.

PS: Why powers of two? I don’t see anything natural about that. Real numbers seem more natural to me.

PPS: I don’t think we have to change coordinate system to make kilometre usable. I can navigate using degrees and kilometres. Swedish pilots apparently managed as well. One-in-sixty rule, sometimes used to defend nautical mile, works with any unit.

Last Edited by Martin at 22 Apr 14:10

But Gon is as arbitrary as degrees.

I see only two “natural” units for angles – radians and subdividing full angles by powers of two. The latter is what Garmin uses (by 2^32) quite a bit, internally.

LSZK, Switzerland

Postponing the change doesn’t help. Aviation is relatively young and, as the Chicago Convention proves, it’s not a novel idea. Naval world is a different story. Coordinate system might be taught in schools but navigating the old fashioned way is not something general public uses on a regular basis. These days, no understanding of the coordinates is necessary. Even back in the day, it was something a scout could do, but I doubt people did a lot of navigation. Not to mention, the principles stay the same. I don’t think we have to concern ourselves with coordinate system used for road maps (unless you fly using one ). If geodesists can use kilometres, so can we.

Last Edited by Martin at 22 Apr 12:52

This will be a nice thread drift… I wouldn’t call it a good reason. It’s not like kilometre is scalewise vastly different (like parsec is). And there are other units for angles as well. You might be in particular interested in gradian (grad/ gon), sometimes referred to as a metric degree. It’s no coincidence it’s used in geodesy. Metre was originally defined in the same fashion as nautical mile, just using different degrees.

I know about gon. Certainly using metres and gon would be best, but that would require a general change of coordinate system — not only in aviation — as we would certainly not want aviation to use units of latitude and longitude which are different from what everyone else use. I see such a change as totally impossible.

OTOH, changing altitude units to metres would be possible.

Last Edited by Airborne_Again at 22 Apr 12:20
ESKC (Uppsala/Sundbro), Sweden

This will be a nice thread drift… I wouldn’t call it a good reason. It’s not like kilometre is scalewise vastly different (like parsec is). And there are other units for angles as well. You might be in particular interested in gradian (grad/ gon), sometimes referred to as a metric degree. It’s no coincidence it’s used in geodesy. Metre was originally defined in the same fashion as nautical mile, just using different degrees.

AFAIK metric units used to be more widespread in aviation before ’50s. Back in 1944 at the Chicago Convention it was decided that metric units should be the primary standard in aviation. And that, at least temporarily, units like knot and nautical mile should be retained because they have a “special place in aviation.” IIRC. And what is the situation today? Are metric units primary? I suppose we have the Americans to thank for this.

If someone can more easily navigate using nautical miles, so be it. I see no reason to outlaw it. Just as I see no reason for such units to be the standard for all of aviation. I see no benefits in it.

Last Edited by Martin at 22 Apr 12:17

Metric instruments are definitely used in the VFR world in the continental Europe.

In France the DR400 has an ASI labeled in km/h.

Edit: and some older (US-built) airplanes have ASIs labeled in mph.

Last Edited by Aviathor at 22 Apr 11:35
LFPT, LFPN

There is actually a good reason for using nautical miles. Not so with feet.

Last Edited by Airborne_Again at 22 Apr 10:52
ESKC (Uppsala/Sundbro), Sweden

Soaring in Sweden still use metric as originally it was heavily influenced by the military.

Not just in Sweden. Metric instruments are definitely used in the VFR world in the continental Europe. I would say most commonly in gliders but I have seen them in modern aerobatic planes as well (POH is then in metric units as well). Frankly, I was surprised that those antiquated units are used in European aviation.

All militaries of member states of NATO should use metric units. Even US military does to some extent. Well, except for air forces. So ground troops use kilometres and aviators nautical miles.

Last Edited by Martin at 22 Apr 08:38

In “Europe”, the USSR region still uses metres for altitude. The Swiss military used to use it till some years ago (I remember their VFR charts, and thinking “those cows look bigger than they should be”).

So did the Swedish military (as well as km/h and m/s rather than knots and fps). They switched to feet etc. when our parliament decided that the Swedish armed forces were going to be used for international missions rather than defending Swedish territory.

Soaring in Sweden still use metric as originally it was heavily influenced by the military.

ESKC (Uppsala/Sundbro), Sweden

In 2004, there was only one “ICAO chart” for Switzerland. See here, somewhere… It mixed both feet and metres on the same chart! It probably killed a number of people.

Back to the OP, can anyone think why the worked example in the QB showed the wrong GS?

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