How do you compute distance between 2 Lat/Long

[AvroJockey]

I know that 1 minute Lat is equal to 1 NM, but I was never taught how to compute the distance between two set of lat/long coordinates.

Is there an easy (mental math) formula that gives you a rough figure?

Jockey

 

[Spooky 2]

I know that 1 minute Lat is equal to 1 NM, but I was never taught how to compute the distance between two set of lat/long coordinates.

Is there an easy (mental math) formula that gives you a rough figure?

Jockey

I don't mean to be a smart ass but I think the best way would be by the use of the Jepp PV-5 plotter.
I can't recall any formula that works for this but obviously there is one as it is used to build computer flight plans every day. Navigators typically use the Universal 10 degree tables for this activity. I have sets for the West Pac and N Atlantic, but not much else. Do a Google search for Universal 10 degree tables and see what you come up with.

Good Luck

 

[MD11Drvr]

When I went through INDOC at ATI in 1999 they gave us a copy of "Nav Tables" that gave Nautical Miles between every 10 degrees of Longitude between two line of Latitude. I wish I still had them and in fact if anyone knows of a link to such a thing I would love to have a copy of those again. They would be very handy if you were manually working out a flight plan across the North Atlantic.....

 

[CitationLover]

I know that 1 minute Lat is equal to 1 NM, but I was never taught how to compute the distance between two set of lat/long coordinates.

Is there an easy (mental math) formula that gives you a rough figure?

Jockey

here is the EXACT methodology. perhaps a shortcut can be seen from this.

we will use ORD (41 58' 42.972" N x 87 54' 17.429" W) to LAX (33 56' 33.1301" N x 118 24' 29.068" W)

convert to decimals so for ex. 41 + (58 + (42.972/60))/60 = 41.9786033. It will be negative if S and W. Thus ORD (41.9786033, -87.904841) to LAX (33.9425361, -118.40807).

convert the decimals values to radians by multiplying them by PI/180. so for ex. 41.9786033 x PI / 180 = .73266484. Thus ORD (0.73266484, -1.5342289) to LAX (0.59240901, -2.066108).

calculate the SIN and COS of each latitude and longitude value.

The formula is:

ARCCOS (SIN(Lat1) SIN(Lat2) + COS(Lat1) COS (Lat2) COS(Long2-Long1)) x (180/PI) X 60

The 180/PI is to convert back to degrees and 60 is the number of nm per degree of lat/long.

For ORD to LAX the value is 1512.00272.

Basically you are measuring arc distance and that is where the math comes from. The radius of the earth is a constant and thus from the center of the earth to each lat/long coord is the radius of the earth plus its field elevation above MSL. then with two sides of the triangle known and the angle between the two calculated (the arc cosine value) the arc length can be calculated.

http://www.themathpage.com/aTrig/arc-length.htm

Your frequent flier miles will be credited.....

 

[PositiveRate]

And the award for the most impressively nerdy post of the year goes to.....

 

[GuppyWN]

Citation Lover,

My man. I am not worthy. I feel incapable of any worthwhile contribution from this point on.

WOW.

Gup

 

[jimcav]

Thats over my former dumb jock head.

 

[snow-back]

F + M + S

Works great!

 

[CitationLover]

the formula believe it or not was taught in the old days of aviation. barry schiff actually 'splained it to me over the phone (i was flying with his son).

and as usual with math formulas there are more ways to skin the cat.
http://www.movable-type.co.uk/scripts/latlong.html
http://www.movable-type.co.uk/scripts/latlong-vincenty.html
this one does have some rules of thumb: http://www.meridianworlddata.com/Distance-Calculation.asp

 

[joe_pilot]

here is the EXACT methodology. perhaps a shortcut can be seen from this.

we will use ORD (41 58' 42.972" N x 87 54' 17.429" W) to LAX (33 56' 33.1301" N x 118 24' 29.068" W)

convert to decimals so for ex. 41 + (58 + (42.972/60))/60 = 41.9786033. It will be negative if S and W. Thus ORD (41.9786033, -87.904841) to LAX (33.9425361, -118.40807).

convert the decimals values to radians by multiplying them by PI/180. so for ex. 41.9786033 x PI / 180 = .73266484. Thus ORD (0.73266484, -1.5342289) to LAX (0.59240901, -2.066108).

calculate the SIN and COS of each latitude and longitude value.

The formula is:

ARCCOS (SIN(Lat1) SIN(Lat2) + COS(Lat1) COS (Lat2) COS(Long2-Long1)) x (180/PI) X 60

The 180/PI is to convert back to degrees and 60 is the number of nm per degree of lat/long.

For ORD to LAX the value is 1512.00272.

Basically you are measuring arc distance and that is where the math comes from. The radius of the earth is a constant and thus from the center of the earth to each lat/long coord is the radius of the earth plus its field elevation above MSL. then with two sides of the triangle known and the angle between the two calculated (the arc cosine value) the arc length can be calculated.

http://www.themathpage.com/aTrig/arc-length.htm

Your frequent flier miles will be credited.....

As far as geeky posts go, I have to admit I was gonna reply to this. I'm getting ready for grad school and haven't had math in 20 years, so I'm starting over this semester with....Trig!

WARING GEEK CONTENT: Doesn't the earth's radius actually get smaller as you progress away from the equator?

I need a beer.

-JP

 

[CitationLover]

WARING GEEK CONTENT: Doesn't the earth's radius actually get smaller as you progress away from the equator?

hence the vincenty variation above (http://www.movable-type.co.uk/script...-vincenty.html). it assumes....

For the benefit of the terminally obsessive (as well as the genuinely needy), Thaddeus Vincenty (‘TV’) devised formulae for calculating geodesic distances between a pair of latitude/longitude points on the earth’s surface, using an accurate ellipsoidal model of the earth.

as the earth is not a perfect sphere.

 

[joe_pilot]

hence the vincenty variation above (http://www.movable-type.co.uk/script...-vincenty.html). it assumes....

as the earth is not a perfect sphere.

I didn't notice your additional post, so as Eddie Murphy, playing the old Jewish man in "Coming to America" would say...

"Acccch-haaaaaaa".

Cheers!

-JP

 

[STL717]

Great Circle Mapper
http://gc.kls2.com/

 

[DrewBlows]

Who gives a sh

 

[fatboyplt]

How about at normal ground speeds in a jet. You pick what norm is. Say at .82, 10mins = 2degrees long, it is a pretty good wag. Try it. Not scientific but it will get you there.
Its a wrap, put it on the plot chart....

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