ARLA/CLUSTER : FW: [HFpack] calculation of distance between points lat/long GPScoordinate (Re:for Guy)

[Miguel Andrade]

-----Mensagem original-----
De: hfpack  yahoogroups.com [mailto:hfpack  yahoogroups.com]Em nome de
darrel
Enviada: sexta-feira, 14 de Abril de 2006 20:30
Para: hfpack  yahoogroups.com
Assunto: [HFpack] calculation of distance between points lat/long
GPScoordinate (Re:for Guy)


For points this close the following approximation is adequate (on scientific
calculator, Basic or spreadsheet)

dlat = lat1-lat2
dlon = (lon1-lon2)*cos(lat1)
dist = sqrt(dlat*dlat + dlon*dlon) * 69 miles

lat1 = 44.6676, lat2 = 44.39545, lon1 = 90.175383, lon2 = 89.802417 giving
26.3 miles
 Up to 100 miles or so this will be better than 1%.  As the points get
farther apart, the fact that we are ignoring the curve of the earth starts
to
matter.
There's a much longer, messier formula (e.g. it's been in some of the ARRL
antenna books under great circle calculations) that does the spherical trig
to get the right answer in all cases.

Many (most?) GPS can tell you this.  E.g. build a route with the points, and
the display of the route often shows the incremental or cumulative
distances.
    Darrel AK6I


--- "guyboucher" <guyboucher  tznet.com> wrote:
> Back packing.
> We have coordinates taken with GPS, now I need program to give mileage
> between points.
> anyone?  If I recieve the program, I can save it for the future.
> radio shop N 44 40 056,W 090 10 523
> Lock shop N 44 23 727,W 089 48 145
> Much thanks in advance. 73 Guy kf9xx  arrl.net
>
>
>
>





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