Compute Distance Between 2 Lat/long points

[puforee]

I need a formula that will work on a form to compute the distance between 2 lat/long points. Miles or Nautical Miles would be fine.

Thanks,

 

[Remou]

You will find a lot of information here:

http://www.meridianworlddata.com/Distance-Calculation.asp

If you do not need great accuracy, Pythagoras should suit.

You may wish to try APIs:

http://code.google.com/apis/maps/documentation/index.html

 

[puforee]

Actually longituted can get real messed up as you go north or south from the equator...so accuracy is importatant.

Thanks for the response.

 

[MichaelRed]

there is at least one EXCELLENT thread on this subject in these (Tek-Tips) fora. I think it was in the VB Forum, bbut not sure. I believe a search for {Latitude Longitude} should find the thread.



MichaelRed

 

[jerryreeve]

what you are actually trying to calculate is "great circle distance" or "Great circle route" the formula's are a bit complicated check out:

http://en.wikipedia.org/wiki/Great_circle_distance

and

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

normally I don't reference wiki but this discussion looked fairly complete.

----------------------------
Hill?? What hill??
I didn't see any $%@#(*$ Hill!!
----------------------------
JerryReeve
Communication Systems Int'l
com-sys.com

 

[MajP]

Two slightly different algorithms

Public Function polarDistanceTwo(decLatStart As Single, decLongStart As Single, decLatEnd As Single, decLongEnd As Single) As Single
Const decToRad = 3.14159265358979 / 180
Const radiusOfEarth = 3963.1
'radiusOfEarth =3963.1 statute miles, 3443.9 nautical miles, or 6378 km
Dim radLatStart As Single
Dim radLongStart As Single
Dim radLatEnd As Single
Dim radLongEnd As Single
radLatStart = decLatStart * decToRad
radLongStart = decLongStart * decToRad
radLatEnd = decLatEnd * decToRad
radLongEnd = decLongEnd * decToRad
If Sin(radLatStart) * Sin(radLatEnd) + Cos(radLatStart) * Cos(radLatEnd) * Cos(radLongStart - radLongEnd) > 1 Then
   polarDistanceTwo = 3963.1 * ArcCos(1)
   Else
   polarDistanceTwo = 3963.1 * ArcCos(Sin(radLatStart) * Sin(radLatEnd) + Cos(radLatStart) * Cos(radLatEnd) * Cos(radLongStart - radLongEnd))
End If
End Function

Function polarDistance(decLatStart As Single, decLongStart As Single, decLatEnd As Single, decLongEnd As Single) As Single
Const decToRad = 3.14159265358979 / 180
Const radiusOfEarth = 3963.1
'radiusOfEarth =3963.1 statute miles, 3443.9 nautical miles, or 6378 km
Dim radLatStart As Single
Dim radLongStart As Single
Dim radLatEnd As Single
Dim radLongEnd As Single
radLatStart = decLatStart * decToRad
radLongStart = decLongStart * decToRad
radLatEnd = decLatEnd * decToRad
radLongEnd = decLongEnd * decToRad
polarDistance = ArcCos((Cos([radLatStart]) * Cos([radLongStart]) * Cos([radLatEnd]) * Cos([radLongEnd])) + Cos([radLatStart]) * Sin([radLongStart]) * Cos([radLatEnd]) * Sin([radLongEnd]) + (Sin([radLatStart]) * Sin([radLatEnd]))) * radiusOfEarth
'                     (cos($a1)*            cos($b1)*             cos($a2)*          cos($b2)          + cos($a1)*            sin($b1)*              cos($a2)*          sin($b2) +          sin($a1)*             sin($a2)        ) * $r
'                 acos((cos($a) *           cos($b) *             cos($c) *          cos($d)) +          (cos($a) *           sin($b) *              cos($c) *           sin($d)) +         (sin($a) *            sin($c)) ) * $r
End Function
Function ArcCos(X As Single) As Single
    If Abs(X) <> 1 Then
        ArcCos = 1.5707963267949 - Atn(X / Sqr(1 - X * X))
    Else
        ArcCos = 3.14159265358979 * Sgn(X)
    End If
    'ArcCos = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
End Function