On 24 feb, 17:48, "Larry Serflaten" <serfla***@usinternet.com> wrote:
> <Zai***@gmail.com> wrote
>
> > I need to run through a recordset with Lat Lon coordinates and find
> > out if they are within X radius from a certain coord.
>
> > The coords are build up like this: 321600 (degrees, minutes and
> > seconds).
> > The centergrid could be for example: 321600, 063312 and the radius 15
> > km.
>
> > Is there a formula to do this?
>
> The formula to use is Pythagoras' theorem.
>
> Convert all measurements to a single scale (such as Seconds) and find the
> difference in Lon and Lat (or X and Y) then use Pythagoras' theorem to see
> if it falls within the desired radius.  Of course that says nothing about the
> complexity added when also considering the curvature of the earth.  In short,
> such a solution would be next to useless at or near the poles....
>
> If the earth's curvature is not taken into account, the solution is simple as the
> short demo below shows. For details on the more accurate formula pertaining
> to a sphere, check out this link:http://www.reference.com/browse/wiki/Great-circle_distance
>
> LFS
>
> Option Explicit
> Dim CX As Single
> Dim CY As Single
> Dim Radius As Single
>
> Private Sub Form_Load()
>     AutoRedraw = True
>     ScaleMode = vbPixels
>     CX = 100
>     CY = 100
>     Radius = 50
>     Circle (CX, CX), Radius
> End Sub
>
> Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
> Dim DX As Single
> Dim DY As Single
>
>   DX = Abs(X - CX)
>   DY = Abs(Y - CY)
>   If Sqr(DX * DX + DY * DY) < Radius Then
>     Caption = "Inside"
>   Else
>     Caption = "Outside"
>   End If
> End Sub