I picked this formula up off the list in May 1997 (I think) and modified it
to give me the
distance in metres
between LON1 LAT1 and LON2 LAT2 in Excel. Unfortunately, I have changed
computers and in the process lost the original message so I am unable to
identify the original donor who
was using it in Foxpro.
I have used it and found it to match the results of the MI distance function
to within 1 metre over about 700 metres - I didn't test it further as that
level of accuracy was ample for my needs.
You can modify the last multiplier (92213.097) to reflect whatever unit of
measure you wish by dividing it by the number of metres in your unit of
measure of choice.
69.093*ACOS(SIN(LAT1*0.01745329252)*SIN(LAT2*0.01745329252)+(COS(LAT1*0.0174
5329252)*COS(LAT2*0.01745329252)*COS((LON2*0.01745329252)-(LON1*0.0174532925
2))))*92213.097
If you get wacky results, it is probably an error in my translation of it
back to a generic formula - if so get back to me & I will re-check it.
For more information, David Ward www.earthwardconsulting.com suggested the
attached references to a similar question back in February
I have checked and the "Formulas" link is still alive although it is not a
definitive answer and I suspect it is essentially the same as the fomula
above:
Try.....
Javascript: http://www.best.com/~williams/gccalc.htm
Formulas: http://forum.swarthmore.edu/dr.math/problems/longandlat.html
----- Original Message -----
From: Bob Young - www.bydesignwales.demon.co.uk
<[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, May 11, 2000 11:23 PM
Subject: MI Accurate distances around the world
> Dear List
>
> This is a general GIS question rather than MI specific.
>
> Does anybody know where I can find a formula for measuring the distance
> from one long, lat to another long, lat anywhere in the world?
>
> I am not worried about the complexity of the formula. I am more
> concerned about the accuracy of the answers obtainable from the formula.
>
> ALSO:-
>
> Does anybody have any experiences ( good or bad ) on the accuracy of the
> answers from MapInfo Professional on distance measurement? Does anybody
> know the method employed within MI Pro?
>
> Thanks,
>
>
> Bob Young
> www.mapsbydesign.co.uk
>
>
>
> --
> Bob Young - www.bydesignwales.demon.co.uk
> ----------------------------------------------------------------------
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