# Some brain power required

Trancelator Guest

Hey,

Heres what i want to do.I need some brain power.

If im on runway 3.Throughout the whole runway there are longitude and latitude co ordinates.

Given that i know the heading of runway 3 say 30 degrees,if i was to stay on the centerline and go back 10nm or how could i figure out the latitude and longitude at a point 10nm from the runway threshold?

Im thinking there should be a way to do this because im keeping my heading constant.

Im trying to work on a new landing system to help keep me centered.
Digital ILS is what it will be.

I might also need some help with someone who could make/program add-ons for Flightsim.

Ryan (737FLIER) First Officer

look at the map.

Guest

How would your system be better than the ILS system we already have?

For your idea, you would need a little trigonometry. You would just need the sine and cosine fuctions to be able to do it, then just figure out your new coordinate.

It's good when people try to create a better way of doing things.

CRJCapt Chief Captain

A point {lat,lon} is a distance d out on the tc radial from point 1 if:

lat=asin(sin(lat1)*cos(d)+cos(lat1)*sin(d)*cos(tc))
IF (cos(lat)=0)
lon=lon1 // endpoint a pole
ELSE
lon=mod(lon1-asin(sin(tc)*sin(d)/cos(lat))+pi,2*pi)-pi
ENDIF
This algorithm is limited to distances such that dlon <pi/2, i.e those that extend around less than one quarter of the circumference of the earth in longitude. A completely general, but more complicated algorithm is necessary if greater distances are allowed:

lat =asin(sin(lat1)*cos(d)+cos(lat1)*sin(d)*cos(tc))
dlon=atan2(sin(tc)*sin(d)*cos(lat1),cos(d)-sin(lat1)*sin(lat))
lon=mod( lon1-dlon +pi,2*pi )-pi

Don't ask me how to work it, I don't have a clue. Good luck! 🙂

Trancelator Guest

Thanks CRJ capt.

Really appreciate it.

That looks like a heck of a forumla thoug.where did you get it?

Ill check it out.
for anyone who interested this is what i want to do.
Picture a runway right.Down the centerline you have a heading of 30 deg.

Move 10 feet to the right and you can still have a heading of 30 deg on the same runway.(when the ils needle centers you are sometimes left or right by a few feet)

So,if you extend the centerline 20nm you will have many lat and lon co-ordinates but only ONE thats exactly center.

So know if i had a program that could work out that lats and longs 20nm back for a 30 deg runway it would compare to what im flying in flightsim and subtract the 2 figures the whole way and give me say a -0.5 , the i would know im left/right and need to correct.

Is this idea possible.i think so.

I find the ILS is very accurate(more so for the autopilot)this would be more for manual flying.(especially for me)

Ill keep everyone posted on how it goes.

CRJCapt Chief Captain

Aviation Formulary V1.43
http://williams.best.vwh.net/avform.htm

Trancelator Guest

WOW!!!

Thats a lot of reading/great resource.

Much appreciated CRJ Capt

Maybe i should just invest my time in figuring out how to land the damn plane with the ILS.

LOL!

CRJCapt Chief Captain

CRJCapt Chief Captain

Trancelator,
I found this map plotting software and thought of you.
http://library.avsim.net/esearch.php?CatID=fs2004misc&DLID=79175