[gradsusr] Calculate distance between latitude-longitude in GrADS

[Davide Sacchetti]

  function dist(lon1,lat1,lon2,lat2)
* Distance between two points on the Earth surface
    _At=6371229
    _PI=3.141592654
    _D2R=_PI/180
    _R2D=180/_PI
    Theta1=lon1*_D2R;Phi1=(90-lat1)*_D2R
    'd sin('Phi1')*cos('Theta1')'
    x1=subwrd(result,4)
    'd sin('Phi1')*sin('Theta1')'
    y1=subwrd(result,4)
    'd cos('Phi1')'
    z1=subwrd(result,4)
    Theta2=lon2*_D2R;Phi2=(90-lat2)*_D2R
    'd sin('Phi2')*cos('Theta2')'
    x2=subwrd(result,4)
    'd sin('Phi2')*sin('Theta2')'
    y2=subwrd(result,4)
    'd cos('Phi2')'
    z2=subwrd(result,4)
*    x=y1*z2-y2*z1
*    y=x2*z1-x1*z2
*    z=x1*y2-x2*y1
*    d2=x*x+y*y+z*z
    Alpha='acos( cos('Phi1')*cos('Phi2') +
cos('Theta1'-'Theta2')*sin('Phi1')*sin('Phi2'))'
*    'd asin(sqrt('d2'))'
*    'd acos('Alpha')'
    'd 'Alpha
*say 'T,P: 'Theta1' 'Phi1
*say 'T,P: 'Theta2' 'Phi2
*say 'A,cA: 'Alpha' 'subwrd(result,4)
  return (subwrd(result,4)*_At)     





On Mon, 2015-02-16 at 07:45 +0000, PHILBERT LUHUNGA wrote:
> Hi does any one knows how to compute distance between two latitude and
> longitude points in GrADs. I have two points
> lon1=30
> lat1=-6
> lon2=30.6
> lat2=-6.4
> 
> 
> please help
>  
> AS EVER 
> LUHUNGA 
> 
> -------------------- 
> Philbert Modest Luhunga 
> University of Pretoria  
> Department of Geography,Geoinformatics and Meteorology 
> Private Bag X20 Hatfield 0028 South Africa 
> Tel +27 (0) 12 420 5164 
> Fax +27 (0) 12 420 6385 
> Mobile:+ 27826228060 
> Email address: philuhunga at yahoo.com
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-- 
Davide Sacchetti
Centro Funzionale Meteo Idrologico di Protezione Civile della Regione Liguria
ARPAL Unità Tecnica Complessa di livello Regionale
V.le Brigare Partigiane 2 16121 Genova (I)
tel: +39 010 6437535                    fax: +39 010 6437520
mail: davide.sacchetti at arpal.gov.it     web: www.meteoliguria.it