Rounding : Magnetic Headings

Well, I suppose that would actually be any heading in FS9. I also suppose it really doesn't matter much when you're on final but being a bit pedantic, how should a pilot address 12.20, 12.50 and 12.90 in theory, round-up or round-down. In practice (at least for me) it doesn't matter to much as I fly steam more that digital. Still am interested in what's what though.

 

Please advise and thanks!

I have only ever seen a magnetic heading referenced in whole numbers. Where are you seeing headings referenced in decimals ?

I have only ever seen a magnetic heading referenced in whole numbers. Where are you seeing headings referenced in decimals ?

 

Database information comes in different formats. At the end of the day, some headings are whole numbers and some are fractional. As I was saying, my steam gauges don't discern fractional from whole numbers. Be that as it may, there are many headings which contain both a whole number and a fractional part. A decimal heading if you would and if that is a proper term.

 

For Example...

 

ICAO   Rwy    True    Mag
KLAX   06L    82.97   68.94

 

For most people, the rounding of the KLAX headings (as listed above) will be obvious. However, from the perspective of the code required to represent the round in an application, the techniques can vary from bankers to floor, ceiling, and a variety of other formats based on the requirement of the result.

 

From a steam gauge perspective, it could be considered irrelevant. With a bank, paying out an interest rate to your account, it becomes very relevant. But in the case of this question, the only relevancy is the method which FS9 is using in the sim. That is, to round the display of decimal headings, vis a vis, why sometmes only whole numbers are displayed.

 

I can take test flights and make a determination on my own. What I'm after is a simple heads up as to which method FS9 is actually using. That way I don't have to guess (or take a test flight). Hope that makes better sense!

 

EDIT: Thanks for your response as well!

Looking at runways using AFCAD it looks like FS9 measures true headings to 2 decimals. After applying magnetic declination these are recorded as magnetic headings to 1 decimal.

 

Maybe FS9 does no rounding at all and that heading is always recoeded to 1 decimal place ?

 

Your own aircraft's heading may be read by FS9 as a decimal or not, I have no idea how you could tell. If you press Shift-Z it tells you a heading in whole numbers, maybe it is rounding your heading? If so I would expect it to follow usual accepted practice of rounding the significant decimal place up if it is 5 or more, or down if it is 4 or less.

I'd love to fly with a pilot who can hold a mag heading of 68.94!!!!

 

Mike

I used to do Orienteering, using a compass and a topo map of the area to navigate. I would have loved to be able to hold 68.94 on FOOT!

Some beautiful hikes in the redwoods doing that. Sadly, once I got to Yuma, the thrill kinda went out of hiking. Miserable place...

Pat☺

Love that kitty sergeant!

 

Good content with this post. If anything else, its showing newbs how to properly interpret navigational data. I think the best way to test this would be to sit your craft on an apron somewhere. Have a known list of three, decimal magnetic ILS runway headings, ready and in hand.

 

In the default GPS 500, create a waypoint (-D->) to an airport containing one of the ILS runways. Then select the runway's ILS approach and activate it. Finally, go to the flight plan page of the GPS and check the runway bearing. It usually displays a whole number magnetic heading for the runway. Do the same for the remaining two airports/runways.

 

The 90 degrees (in the following list) could be any whole number heading. What's important is the .1, .5, and .9:

 

90.1

90.5

90.9

 

My guess is that all three of the above headings will round to 91 magnetic, which would be a ceiling formatted round. Point .9 of a degree is quite a distance when running calculations in an app. The difference of viewing Niagara Falls from a safe distance to beaming into the falls in a head to toe declination. I suppose most people would not want that to happen, unless of course, you're Xander Cage.

 

Cool...

I think you'll find if the runway heading is 68.94° you'll need to fly 68.94° to align with it, I don't see where you get the idea that something is being rounded, cieled or floored to the nearest integer. I just flew the ILS Rwy 6L at KLAX with a HDG gauge that reads one decimal and here's what I found with zero wind and the AP locked on to the ILS:

 

http://www.cat-tamer.com/flightsim/atchmnts/fs9_rwy6l_klax.jpg

 

 

...or am I missing the point completely? :)

May I ask where you got the HSI? I know it's not FS9 default. Most HSI (HSI's??) I've seen/installed don't have a digital display feature. The only digital readout I seem to recall in FS9 is the Magnetic Compass add-on, which has a single decimal digit, and theres a digital display in the DC-3 up-to-date cockpit by Norm Hancock which only has a whole number display, and the Training C-172 from the Navigation Training for Flight Sims site, which also only has a whole number display.

I LIKE that HSI, I've just never seen it before. May I ask where it came from? I would love to be able to install it on some of my planes, is all :) I do that. I find a gauge I like I put it into whatever plane I am using. Not too worried about "realistic".

Pat☺

I think you'll find if the runway heading is 68.94° you'll need to fly 68.94° to align with it, I don't see where you get the idea that something is being rounded, cieled or floored to the nearest integer. I just flew the ILS Rwy 6L at KLAX with a HDG gauge that reads one decimal and here's what I found with zero wind and the AP locked on to the ILS:

...or am I missing the point completely? :)

 

That is a great looking cockpit, really nice! Is that your own work. It appears the HSI gauge is rounding off the last digit and the default GPS shows no decimal places as well. However, I think you've illuminated an important concept here, and that would be the dependency of the gauge which is displaying the data.

 

The HSI in the craft is showing a floor style of rounding. What's important is the information provided that a heading is a heading. No matter what. I suppose that means to become familiar with each gauge which you're using, and note the values it displays. As it seems, that is True-ly the answer.

Pat, there's a good chance Jim Robinson created it himself:), he's great with that kind of stuff!!:):D

May I ask where you got the HSI?

 

Lol, I did make it. It started out life for the default FS9 Skyhawk panel when I discovered the default DG was inaccurate. An early iteration of the gauge can be downloaded here:

 

https://www.flightsim.com/vbfs/fslib.php?do=search&fname=c1xx_dg.zip

 

The gauge linked above doesn't have the toggle-able digital displays unfortunately but it does have tooltips that read Magnetic HDG and AP HD hold value depending on where you hover (only whole number values, sorry).

 

Later when I got FSX I swiped the 2D panel .bmps from the FSX Skyhawk and built myself a custom panel for FS9 which I also merged with the Carenado external model/VC and RealAir freeware flight dynamics. I added more custom gauges and also added the toggle-able digital displays. It was never considered "done" so I never released it but maybe I could look at bundling up the gauges somehow.

 

 

It appears the HSI gauge is rounding off the last digit and the default GPS shows no decimal places as well.

 

It's rounding one place right of the decimal because that's what it's programmed to do with:

 

%((A:Plane heading degrees magnetic,degrees))%!3.1f!°

 

!3.1f! means 3 places to the left and one place to the right. If you wanna go 2 places you'd use !3.2f! but the last digit would never be still because you can't fly that straight, lol.

 

The HSI in the craft is showing a floor style of rounding

 

No it's not, it's "NEAR-ing" (rounding to the nearest tenth of a degree)

 

Jim

Yup and for me, its a rarity to use the decimal places as I fly mostly steam. What I was interested in is finding out what to expect. The default GPS only shows whole numbers but the data shows a fractional value. The HSI may be using truncation but at the end of the day, the default GPS still is rounding.

 

From a practical perspective and using steam, its not relevant. But I think its important to note that standards do very. So would it be safe to say that the rounding occurs after the sim engine, and not in it. Anyway, I downloaded your cool gauge and have an aircraft which it will be fun to use it in. I really like the work you did on the cockpit as well.

 

Pretty cool and thanks for the comments Jim! They're very helpful.

Everyone please repeat after me....

 

DG, not an HSI

 

 

DG, not an HSI

 

 

DG, not an HSI

 

:pilot::p:pilot:

 

Thanks much.

 

peace,

the Bean

Everyone please repeat after me....

DG, not an HSI

 

Yeah, I saw that too but didn't want a legitimate question get buried in unnecessary distractions. The important point, however it was arrived to, is the conclusion that all rounding is done at the discretion of the developer, outside of the sim engine. That is the varying standard and that is what I noticed as well.

 

It is the why of when I look at the GPS, its rounded. The question of how pilots deal with decimal data has only been answered through innuendo, and could have been addressed better. But all's well that ends well as it should. For all you would-be computer pilots, I suppose the advice would be when steam landing, simply wing-it :)

 

Thanks to everyone!

...unnecessary distractions.

My specialty.

 

The question of how pilots deal with decimal data has only been answered through innuendo, and could have been addressed better.

 

The simple answer is, they don't.

 

Trying to track a specific mag heading with a whiskey compass is impossible, decimal or not.

 

Not much easier with a DG in anything but smooth air. Add in a crosswind and fuget aboudit.

 

RW flying is not an as exact science as it is behind the comfort of your desk.

 

Tracking a VOR radial is tracking a radio signal, not a magnetic heading.

 

All in all, you are making a small mountain out of nothing.

 

peace,

the Bean

Thank you Mr. Robinson! I appreciate the answer, and the gauge :)

 

Mr. Bean: I apologize. DG not HSI! I sit corrected.

 

For all you would-be computer pilots, I suppose the advice would be when steam landing, simply wing-it

BOOO!!

Terrible pun!

:D ;) :pilot:

I love it. Puns are the best, or worst, form of humor :)

Pat☺

Hey guys, please read this...

 

Well, I suppose that would actually be any heading in FS9. I also suppose it really doesn't matter much when you're on final but being a bit pedantic, how should a pilot address 12.20, 12.50 and 12.90 in theory, round-up or round-down. In practice (at least for me) it doesn't matter to much as I fly steam more that digital. Still am interested in what's what though.

 

That's the original question and please note the word "theory". For some reason it was booed in the end by a flying cat and a string bean. I still love that cat and the bean is pretty green...but I have the result that I needed.

 

The smiles over here with my compliments!

Flyer8... If you read Pat's last, his Booo was not for your theory, but his weak, even bad pun as he responded to the Bean. As for the Bean, everything he said was 100% on target; he never boooed your theory, simply pointed out how irrelivant it was. As a pilot with a reasonable amount of hours in a variety of airplanes, I can assure you, Beans description of how things work and are done is accurate!

 

how should a pilot address 12.20, 12.50 and 12.90 in theory, round-up or round-down.

 

That's the original question and please note the word "theory".

 

There is no need to round up/down. All charts and procedures are in whole numbers of heading/course. That is what you fly.

 

I cannot think of a single situation where a pilot is presented with a heading/course that contains a decimal, and needs to turn it into a whole number.

 

In theory ? Follow usual mathmatical practice and round up a 0.5 or more.

Flyer8... If you read Pat's last, his Booo was not for your theory, but his weak, even bad pun as he responded to the Bean. As for the Bean, everything he said was 100% on target; he never boooed your theory, simply pointed out how irrelivant it was. As a pilot with a reasonable amount of hours in a variety of airplanes, I can assure you, Beans description of how things work and are done is accurate!

 

Yup, I noted that as well, and my question was answered!

 

Thanks for the help...

There is no need to round up/down. All charts and procedures are in whole numbers of heading/course. That is what you fly.

I cannot think of a single situation where a pilot is presented with a heading/course that contains a decimal, and needs to turn it into a whole number.

In theory Follow usual mathmatical practice and round up a 0.5 or more.

 

Yeah, I agree. Other than seeing the underlying nav headings in third party apps, I haven't run into a situation where I've used it in the sim. Since I use mostly steam gauges and for me, it could be considered irrelevant. Now I haven't had the time to test the GPS rounding, but your advice sounds reasonable as well.

 

Thanks for the head up!

Thank you Mr. Robinson! I appreciate the answer, and the gauge :)

 

Mr. Bean: I apologize. DG not HSI! I sit corrected.

 

BOOO!!

Terrible pun!

:D ;) :pilot:

I love it. Puns are the best, or worst, form of humor :)

Pat☺

 

Hey Phantom, don't take any exceptions to your booo...as I didn't. I liked your booo and thought it be both fun and totally appropriate! Like that kitty as well...

 

Best Regards!

To think this out, I would 'overdo it' in an imaginary example.

lets say you have rw-1, 10 degrees, and it is actually 10.4 degrees.

Overdoing, in imaginary example, lets say its Rw-1, 10 degrees, but the actual heading is 20 degrees.

what would you do.

 

fly to the airport at heading 10 degrees, then 2 or three miles out or so you would have to swerve strongly left, fly for a bit, and then swerve strongly right to get in line with the runway.

 

If the difference is just a two tenths of a degree, as in the first example, the swerve is of course much less.

 

That example at the top of this post:

lets say you have rw-1, 10 degrees, and it is actually 10.4 degrees.

if my HSI indicated only full degrees I would fly towards the airport at 10 degrees. (10.4 is closest to 10)

then swerve slightly left a few miles out,

and swerve right again.

 

By that time the runway would be in view. Landing is visual.

I would just have this in my mind to be able to better anticipate.

 

I would round anything below 0.5 down to 0

0.5 and above to 1

(the nearest whole number basically.)

 

----------------

In an ILS landing situation there is no need for all of this. The localiser puts you on the correct heading anyway. decimals and all.

 

-----------------------------

(To be honest, I don't think I ever even saw a decimal heading myself.)

My specialty.

 

 

 

The simple answer is, they don't.

 

Trying to track a specific mag heading with a whiskey compass is impossible, decimal or not.

 

Not much easier with a DG in anything but smooth air. Add in a crosswind and fuget aboudit.

 

RW flying is not an as exact science as it is behind the comfort of your desk.

 

Tracking a VOR radial is tracking a radio signal, not a magnetic heading.

 

All in all, you are making a small mountain out of nothing.

 

peace,

the Bean

 

Bean! Just involved in a fact finding mission here. GPS 500 is telling me one thing, Data is saying another format is being applied to it. Not trying to make a mountain, just a list or actually, how to format an existing list of about 57, 657 rows of data I have.

 

So as I said to Mr Phantom, I also say to Mr Bean. Don't take an exception to the mountain, as I have not as well. I've got the answer I was looking for and it came to me directly after the Jim's post. That was awhile ago now...but thanks for the response as it is helpful, and so are you!

 

Best Reards too...

 

AN EDIT: That would be 59,567 rows of runway data keyed on the ICAO. Nice dataset!