at this url

http://www.movable-type.co.uk/scripts/latlong-vincenty.html

There is an accurate formula for calculation of distance between two gps coordinates. It is best to go to that page. :

I have these fields "Lat1", Lat2, lon1, lon2 and distance.

I would like to implement this formula into a filemaker file.

Can anyone help with this.

Here is the forumla from that page

a, b = major & minor semiaxes of the ellipsoid

f = flattening (a−:/a

φ1, φ2 = geodetic latitude

L = difference in longitude

U1 = atan((1−f).tanφ1) (U is ‘reduced latitude’)

U2 = atan((1−f).tanφ2)

λ = L, λ′ = 2π

while abs(λ−λ′) > 10-12 { (i.e. 0.06mm)

sinσ = √[ (cosU2.sinλ)² + (cosU1.sinU2 − sinU1.cosU2.cosλ)² ] (14)

cosσ = sinU1.sinU2 + cosU1.cosU2.cosλ (15)

σ = atan2(sinσ, cosσ) (16)

sinα = cosU1.cosU2.sinλ / sinσ (17)

cos²α = 1 − sin²α (trig identity; §6)

cos2σm = cosσ − 2.sinU1.sinU2/cos²α (18)

C = f/16.cos²α.[4+f.(4−3.cos²α)] (10)

λ′ = λ

λ = L + (1−C).f.sinα.{σ+C.sinσ.[cos2σm+C.cosσ.(−1+2.cos²2σm)]} (11)

}

u² = cos²α.(a²−b²)/b²

A = 1+u²/16384.{4096+u².[−768+u².(320−175.u²)]} (3)

B = u²/1024.{256+u².[−128+u².(74−47.u²)]} (4)

Δσ = B.sinσ.{cos2σm+B/4.[cosσ.(−1+2.cos²2σm) − B/6.cos2σm.(−3+4.sin²σ).(−3+4.cos²2σm)]} (6)

s = b.A.(σ−Δσ) (19)

α1 = atan2(cosU2.sinλ, cosU1.sinU2 − sinU1.cosU2.cosλ) (20)

α2 = atan2(cosU1.sinλ, −sinU1.cosU2 + cosU1.sinU2.cosλ) (21)

[color:blue]Might there be a way to fill in the form from FILEMAKER in some sort of calculation to get the coordinates on the web page and get and retreive an answer back to filemaker throught a script?

Edited April 28, 200817 yr by Guest

There was a plugin for Filemaker Pro up to version 7 which did the conversions very nicely and sold for $99. out at AU, I believe. It is still listed under LatitudeZERO if you do a search and include the words Filemaker Pro.

I did not buy it.

There are 2 Custom Functions, at:

http://www.briandunning.com/filemaker-custom-functions/results.php

Do a search for "latitude"