Why shouldn't aviation switch from magnetic to true north?

NoHeat said:
The Earth's magnetic field is constantly changing. That's what this is all about. So we have to constantly be busy, and spending money, adjusting fixed things like runway orientations as the field changes. It would be so much easier and cheaper to leave these fixed things alone, and that can be done simply by referencing them to true north which is also fixed.
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True north changes too. Enough so that star charts are all related to an "epoch", generally every 50 years...current ones will be Epoch 2000
 
ebykowsky said:
Not to mention... GPS can figure out magnetic north just fine.
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You'd want to make an operable GPS a requirement for VFR flight?

Even if you did, GPS doesn't give you your true or magnetic HEADING, it gives you your TRACK. You'll need something more sophisticated than a VFR GPS to get a true HEADING display.

Shepherd said:
There is no reason on earth Metams and all the other weather info can't be posted in plain English.
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For those of us who read those reports daily (mostly professional pilots) it is FAR easier and faster to read the raw METAR/TAF format than it is to read plain English reports. There are plenty of software options for you to have your weather reports decoded. Use those options and leave the raw reports for the rest of us.
 
Ghery said:
That is it, right there. Oh, and that's the way we've always done it. :D
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Like this? :lol:


Start with a cage containing five monkeys. Inside the cage, hang a
banana on a string and place a set of stairs under it. Before long, a
monkey will go to the stairs and start to climb towards the banana. As
soon as he touches the stairs, spray all of the other monkeys with
cold water.

After a while, another monkey makes an attempt with the same result
all The other monkeys are sprayed with cold water. Pretty soon; when
another monkey tries to climb the stairs, the other monkeys will try
to prevent it.

Now, put away the cold water. Remove one monkey from the cage and
replace it with a new one. The new monkey sees the banana and wants to
climb the stairs. To his surprise and horror, all of the other monkeys
attack him.
After another attempt and attack, he knows that if he tries to climb
the stairs, he will be assaulted.

Next, remove another of the original five monkeys and replace it with
a new one. The newcomer goes to the stairs and is attacked. The
previous newcomer takes part in the punishment with enthusiasm!
Likewise, replace a third original monkey with a new one, then a fourth, the the fifth.

Every time the newest monkey takes to the stairs, he is attacked. Most
of the monkeys that are beating him have no idea why they were not
permitted to climb the stairs or why they are participating in the
beating of the newest monkey.

After replacing all the original monkeys, none of the remaining
monkeys have ever been sprayed with cold water. Nevertheless, no
monkey ever again approaches the stairs to try for the banana. Why
not? Because as far as they know that's the way it's always been done
around here.
 
Larry in TN said:
Even if you did, GPS doesn't give you your true or magnetic HEADING, it gives you your TRACK. You'll need something more sophisticated than a VFR GPS to get a true HEADING display.
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Actually, a track is a more useful bit of information than a heading anyway.
 
Earth_Magnetic_Field_Declination_from_1590_to_1990.gif
 
Ron Levy said:
Surface winds are reported as magnetic so they match up with runway numbers. Only winds aloft are forecast as true.
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I'm not sure you meant that. METARs and TAFs report and forecast wind direction relative to true north (AC 00-45G). The PIREP is the only text product I could find in which magnetic is used. But my understanding is that the true to magnetic conversion is done for you when broadcast over the radio (e.g. ATIS).
 
NoHeat said:
Who would have to?

If we had a system of navigation that is entirely based on true north, almost nobody would have to convert anything. The only pilots who would need to do so are (1) those who normally don't use GPS, and (2) those who have a failure of their GPS or electrical system. These two kinds of pilots can still navigate using a true-north navigation protocol - they can do so using their magnetic compass, or heading indicator that is set by magnetic compass. To do so, they would just have to add or subtract a small number.

It would be so much better to slightly inconvenience those few than to cause a great cost by so many. The latter is our current system.
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I don't think it's a good idea to increase the workload of someone who is experiencing an equipment failure.
 
Old Geek said:
That's not clear.

You only have to do it once. You have to re-align the VOR's and renumber the runways every time the magnetic variation changes a couple of degrees. Change everything to true and you'll never have to do it again.
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I don't think there's any chance at all of getting the whole world to agree to the change, and it would sure be a nightmare for pilots who fly internationally if they had to keep track of which countries were on the magnetic north standard and which were on the true north standard.
 
It's not like a magnetic shift sneaks up on you. I'm pretty sure there has never been the need to reschedule having the runway numbers repainted outside of regular maintenance just because magnetic north has all of a sudden shifted. As far as charts go, many things change and they have to be revised on a regular schedule anyway,

In other words, the actual cost in dollars that can be attributed solely to using magnetic north as a reference is basically ZERO.
 
Neal Howard said:
Nobody gets into a no-electrcal-system aircraft and hauls off on a long xc to somewhere they've never been before anymore using only a whisky compass and vfr sectionals. They've at least got a handheld GPS or at minimum a gps-equipped smartphone or tablet. Well, maybe if they're trying to do something "nostalgic" (read that as "freakin' retarded").
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I guess I'm either nobody or "freakin retarded" as I've made a couple trips sans GPS by following my progress on a sectional. It's actually kinda fun.
 
Neal Howard said:
Nobody gets into a no-electrcal-system aircraft and hauls off on a long xc to somewhere they've never been before anymore using only a whisky compass and vfr sectionals. They've at least got a handheld GPS or at minimum a gps-equipped smartphone or tablet. Well, maybe if they're trying to do something "nostalgic" (read that as "freakin' retarded").
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I did it on my first solo cross country as a student. DG failed just after take off and started spinning. It was 1993 and not many people were using handhelds then, so it was compass and sectional. Found the destination (JYL) according to my plan.

I love technology but I think it's sad how much folks are dependent on it. Everyone's gotta have a GPS, ipad with Fore Flight, XM WX, TIS-B, TAWS, etc, etc, etc. How the heck did pilot's survive prior to the 1990s? When a pilot doesn't have the confidence to plan a flight and then go on a cross country with a compass and a sectional, then they have no business being in the air. It's not even like it's that hard to do. Navigating at tree top level with a 1:50,000 map is far more difficult. :yes:
 
Just this past weekend we flew past a runway with a bright white 18 on it and a much more worn 17 just beyond it. Don't know how often, but runways do get renumbered. My airport, of course just has Northbound and Southbound runways. You can tell which is which by looking to see the direction toward the sun and gauging by the time of day.
 
N801BH said:
Agreed.. Declination is a very small correction based on latitude. The Op's point is any GPS can convert mag to true easiely.. For the die hard, old school pilots they can stil use a mag compass and do the correction for variation in their head...
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Very small?

Where I fly, it's 14-17 deg. Enough to make you miss your >50 mile destination by more than decent VFR visibility.

Further north, it can be massive.

And it is a strong function of longitude. Pick up your chart and see where the isogonic lines go. Are they primarily east/west (latitude dependence) or north/south (longitude dependence)?
 
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dmspilot said:
I'm not sure you meant that. METARs and TAFs report and forecast wind direction relative to true north (AC 00-45G). The PIREP is the only text product I could find in which magnetic is used. But my understanding is that the true to magnetic conversion is done for you when broadcast over the radio (e.g. ATIS).
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The way I learned it was that if you read it, it was true and if you heard it then it was magnetic. My primary CFI thought everything was true so we had to discuss it.
 
MAKG1 said:
Very small?



Where I fly, it's 14-17 deg. Enough to make you miss your >50 mile destination by more than decent VFR visibility.



Further north, it can be massive.



And it is a strong function of longitude. Pick up your chart and see where the isogonic lines go. Are they primarily east/west (latitude dependence) or north/south (longitude dependence)?
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Don't confuse declination (bodies in the celestial sphere) and variation (difference between magnetic and true north).
 
Fearless Tower said:
Don't confuse declination (bodies in the celestial sphere) and variation (difference between magnetic and true north).
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I've written control software to point a gyroscopically stabilized telescope. I know what astronomical declination is. The zenith position has it equal to the (geodetic) latitude.

The magnetic variation at KSFO is 14E. It varies along the west coast between 12E (San Diego) and 17E (Seattle). Look it up.

To a surveyor magnetic declination is the same as what a navigator would call magnetic variation. No relation to celestial bodies.
 
MAKG1 said:
Very small?

Where I fly, it's 14-17 deg. Enough to make you miss your >50 mile destination by more than decent VFR visibility.

Further north, it can be massive.

And it is a strong function of longitude. Pick up your chart and see where the isogonic lines go. Are they primarily east/west (latitude dependence) or north/south (longitude dependence)?
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One of us is on the wrong page....... Magnetic (VARIATION) is what determines the correction degree calculation...

Maybe you can help me understand what declination is...
 
Technically, magnetic declination and magnetic variation are the same thing when used in that context.
 
MAKG1 said:
Only if you work in base 5.

Which would make my runway heading 2230.

Rounding shifts the time, but doesn't change its duration.
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My point was..

A runway is marked by it's direction .. Lets say it is runway 13... The direction it pionts to is between 126 to 135... Once the mad variation changes it to 125 or 136 it turns into either 12 or 14... So... once the mag heading changes more the (5) degrees... then the runway number is changed.....

Maybe you guys do stuff differently in California...:dunno:....:mad2:
 
Sac Arrow said:
Technically, magnetic declination and magnetic variation are the same thing when used in that context.
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Probably... back when I sold a few hundred C band satellite systems, declination was ENTIRELY different then mag variation...
 
N801BH said:
My point was..

A runway is marked by it's direction .. Lets say it is runway 13... The direction it pionts to is between 126 to 135... Once the mad variation changes it to 125 or 136 it turns into either 12 or 14... So... once the mag heading changes more the (5) degrees... then the runway number is changed.....

Maybe you guys do stuff differently in California...:dunno:....:mad2:
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Yup, we consider a change from 126 to 136 to be 10 degrees.

When the variation crosses a sector boundary, it doesn't jump to the middle.
 
N801BH said:
My point was..

A runway is marked by it's direction .. Lets say it is runway 13... The direction it pionts to is between 126 to 135... Once the mad variation changes it to 125 or 136 it turns into either 12 or 14... So... once the mag heading changes more the (5) degrees... then the runway number is changed.....

Maybe you guys do stuff differently in California...:dunno:....:mad2:
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If it changed every five degrees lets walk through it....

000/360º = 36
005º = RWY1
010º = RWY2
015º = RWY3
020º = RWY4 (well, we're only off 20º so far)
...
...
090º = 18
...
...
180º = RWY36 - wait what?
 
N801BH said:
Probably... back when I sold a few hundred C band satellite systems, declination was ENTIRELY different then mag variation...
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You're confusing similar and unrelated terms.

The astronomical declination usually gets paired with a right ascension or hour angle. It's one of two spherical coordinates. It makes no sense on its own (unless you're talking about a transit, where the hour angle is there, but understood to be 0 or 12 hours). Just like it makes little sense to talk about latitude without longitude.

Astronomical declination is not a constant for a satellite, unless it's geostationary (then, it is nearly zero, and any deviation is due to the topocentric correction, which can be up to 10 deg or so depending on position on the surface of the earth -- for GPS satellites, which are much closer than geostationary, it's bigger and varies rapidly with time -- and it's a topocentric correction, not a declination correction; there is a correction in hour angle as well).

The magnetic declination is the magnetic variation. No difference. Just two different fields.
 
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N801BH said:
One of us is on the wrong page....... Magnetic (VARIATION) is what determines the correction degree calculation...

Maybe you can help me understand what declination is...
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Do you see that 14 degrees, 30 minutes E notation along a magenta dashed line in the middle of the following chart? Regardless of which word you prefer to use, that's the difference between magnetic north and true north around here.

http://skyvector.com/?ll=38.14692206896055,-122.72191269561108&chart=16&zoom=5
 
EdFred said:
If it changed every five degrees lets walk through it....

000/360º = 36
005º = RWY1
010º = RWY2
015º = RWY3
020º = RWY4 (well, we're only off 20º so far)
...
...
090º = 18
...
...
180º = RWY36 - wait what?
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Ps..... Edit.... In retrospect.. it looks like the cali guy was correct.... It IS 10 degrees based on current direction as I pointed out in my post..:redface::redface:

Huh.... Are you compounding my 5 degrees???:confused:........:D..
 
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MAKG1 said:
To a surveyor magnetic declination is the same as what a navigator would call magnetic variation. No relation to celestial bodies.
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Okay. I think it is safe to say that as pilots, there are far more navigators here than surveyors.
 
Palmpilot said:
Do you see that 14 degrees, 30 minutes E notation along a magenta dashed line in the middle of the following chart? Regardless of which word you prefer to use, that's the difference between magnetic north and true north around here.

http://skyvector.com/?ll=38.14692206896055,-122.72191269561108&chart=16&zoom=5
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The variation is the same here is Jackson.. I get the correction amount........ We are now debating declination - versus- magnetic variation..

get with it man....;)
 
N801BH said:
The variation is the same here is Jackson.. I get the correction amount........ We are now debating declination - versus- magnetic variation..

get with it man....;)
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Nope. It's "small."

Even if you screw up and confuse the irrelevant topocentric correction with a "declination" correction, that is a 6 or 7 degree correction for common mid-continent geostationary satellites from either coast. Still not small.

It's a really, really sucky GPS that doesn't take that into account in its solution. And a really weird compass that has any astronomical declination to correct for.
 
MAKG1 said:
Nope. It's "small."

Even if you screw up and confuse the irrelevant topocentric correction with a "declination" correction, that is a 6 or 7 degree correction for common mid-continent geostationary satellites from either coast. Still not small.

It's a really, really sucky GPS that doesn't take that into account in its solution. And a really weird compass that has any astronomical declination to correct for.
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:rolleyes::rolleyes::rolleyes::rolleyes:.......

Seeya.....
 
Silvaire said:
Really? I've been flying for 45 years and honestly I can't name an airport where they have changed the runway numbers. Maybe some of them have but "constantly"? I think you're making a big issue out of nothing.

Besides, if you're worried about cost wouldn't it cost a lot to have to change every single one of them over night? :dunno:
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Well, I've only been flying for about 14 years and I've see 2 airports change their runway numbers in that time. KCLS and KPUW. So, it happens.

Neal Howard said:
Nobody gets into a no-electrcal-system aircraft and hauls off on a long xc to somewhere they've never been before anymore using only a whisky compass and vfr sectionals. They've at least got a handheld GPS or at minimum a gps-equipped smartphone or tablet. Well, maybe if they're trying to do something "nostalgic" (read that as "freakin' retarded").
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As would be said in German, "Warum nicht?" If you can't navigate with a whisky compass and VFR sectionals, you likely won't pass your private check ride. And rightly so. Yes, the toys are nice, but what happens when (not if) you have a total electrical failure in the airplane? And you don't have a portable GPS? You revert to the compass and sectionals. They work well, too.
 
Ghery said:
Well, I've only been flying for about 14 years and I've see 2 airports change their runway numbers in that time. KCLS and KPUW. So, it happens.



As would be said in German, "Warum nicht?" If you can't navigate with a whisky compass and VFR sectionals, you likely won't pass your private check ride. And rightly so. Yes, the toys are nice, but what happens when (not if) you have a total electrical failure in the airplane? And you don't have a portable GPS? You revert to the compass and sectionals. They work well, too.
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Here in the midwest you don't need a compass. There are so many roads that run north/south and east/west, you're fine without a compass.
 
EdFred said:
Here in the midwest you don't need a compass. There are so many roads that run north/south and east/west, you're fine without a compass.
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Yea but you need water towers with the town name painted on them to figure out where the heck you are!
 
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