> >*FUNCTION distance >*SCATTER memvar >*SELECT * FROM MAPWANTS WHERE > >*----------------------------------------------------------------------* >* Given a pair of lattitude and longitudes, return the approximate >* distance in nautical miles between points A and B. >* >* P_FUNC 1 = DD:MM:SS format, 2 = DD.MMMM format >* P_LT1 Lattitude of point A >* P_LG1 Longitude of point A >* P_LT1 Lattitude of point B >* P_LG2 Longitude of point B >* P_TYPE 0=Nautical Miles, 1=Statute Miles, 2=Kilometers >* >* All lattitude and longitude values are passed as strings in function 1 >* and as numbers in function 2. >* >* Assumes N lattitude and W longitude >* >* Examples: >* a = Distance(1, "33:57:00", "118:24:00", "40:38:00", "73:47:00", 2) >* a = Distance(2, 33.95, 118.4, 40.6333, 73.7833, 2) >* >* Test with http:www.indo.com/distance >* >*----------------------------------------------------------------------* > Function Distance > Parameters p_func, p_lt1, p_lg1, p_lt2, p_lg2, p_type > > Private p_func, p_lt1, p_lg1, p_lt2, p_lg2, p_svdec, p_pi,; > p1_degN, p1_minN, p1_secN, p1_degW, p1_minW, p1_secW,; > p2_degN, p2_minN, p2_secN, p2_degW, p2_minW, p2_secW,; > p_lat1, p_lon1, p_lat2, p_lon2, p_dist, p_type > > p_svdec = Set("decimals") > > Set Decimals To 9 > > If Type("p_type") <> "N" > p_type = 0 > Endif > > If p_type > 2 > p_type = 0 > Endif > > p_pi = Pi() > > Do Case > Case p_func = 1 > p_lt1 = p_lt1 + ":00" > p_lg1 = p_lg1 + ":00" > p_lt2 = p_lt2 + ":00" > p_lg2 = p_lg2 + ":00" > > p1_degN = Val(Left(p_lt1, At(":", p_lt1) - 1)) > p_lt1 = Substr(p_lt1, At(":", p_lt1) + 1) > p1_minN = Val(Left(p_lt1, At(":", p_lt1) - 1)) > p_lt1 = Substr(p_lt1, At(":", p_lt1) + 1) > p1_secN = Val(p_lt1) > > p1_degW = Val(Left(p_lg1, At(":", p_lg1) - 1)) > p_lg1 = Substr(p_lg1, At(":", p_lg1) + 1) > p1_minW = Val(Left(p_lg1, At(":", p_lg1) - 1)) > p_lg1 = Substr(p_lg1, At(":", p_lg1) + 1) > p1_secW = Val(p_lg1) > > p2_degN = Val(Left(p_lt2, At(":", p_lt2) - 1)) > p_lt2 = Substr(p_lt2, At(":", p_lt2) + 1) > p2_minN = Val(Left(p_lt2, At(":", p_lt2) - 1)) > p_lt2 = Substr(p_lt2, At(":", p_lt2) + 1) > p2_secN = Val(p_lt2) > > p2_degW = Val(Left(p_lg2, At(":", p_lg2) - 1)) > p_lg2 = Substr(p_lg2, At(":", p_lg2) + 1) > p2_minW = Val(Left(p_lg2, At(":", p_lg2) - 1)) > p_lg2 = Substr(p_lg2, At(":", p_lg2) + 1) > p2_secW = Val(p_lg2) > > p_lat1 = (p1_degN + ((p1_minN + (p1_secN / 60)) / 60)) * p_pi / 180 >* p_pi * (p1_degN + (p1_minN / 60) + (p1_secN / 3600)) / 180 > p_lon1 = (p1_degW + ((p1_minW + (p1_secW / 60)) / 60)) * p_pi / 180 > p_lat2 = (p2_degN + ((p2_minN + (p2_secN / 60)) / 60)) * p_pi / 180 > p_lon2 = (p2_degW + ((p2_minW + (p2_secW / 60)) / 60)) * p_pi / 180 > > Case p_func = 2 > p1_degN = p_lt1 > p1_minN = 0 > p1_secN = 0 > p1_degW = p_lg1 > p1_minW = 0 > p1_secW = 0 > p2_degN = p_lt2 > p2_minN = 0 > p2_secN = 0 > p2_degW = p_lg2 > p2_minW = 0 > p2_secW = 0 > > p_lat1 = p1_degN * p_pi / 180 > p_lon1 = p1_degW * p_pi / 180 > p_lat2 = p2_degN * p_pi / 180 > p_lon2 = p2_degW * p_pi / 180 > > Otherwise > Set Decimals To &p_svdec > Return 0 > Endcase > >***Method 1 > p_dist = Acos((Sin(p_lat1) * Sin(p_lat2)) + (Cos(p_lat1) * Cos(p_lat2) * Cos(p_lon1 - p_lon2))) > p_dist = Int((p_dist * 180 * 60 / p_pi) +.5) && Distance in Nautical Miles > >***Method 2, with conversion to UTM (Mercator) coordinates > p_er = 6371.315 && Average radius of the Earth > >***Assume N lattitude and W longitude >*** For S lattitude: p_radlat1 = (p_pi / 2) + p_lat1 >*** Others remain the same > p_radlat1 = (p_pi / 2) - p_lat1 > p_radlon1 = (p_pi * 2) - p_lon1 > p_radlat2 = (p_pi / 2) - p_lat2 > p_radlon2 = (p_pi * 2) - p_lon2 > >***Spherical coordinates: x=r*cos(long)sin(lat), y=r*sin(long)*cos(lat), z=r*cos(lat) > p_x1 = p_er * Cos(p_radlon1) * Sin(p_radlat1) > p_y1 = p_er * Sin(p_radlon1) * Sin(p_radlat1) > p_z1 = p_er * Cos(p_radlat1) > > p_x2 = p_er * Cos(p_radlon2) * Sin(p_radlat2) > p_y2 = p_er * Sin(p_radlon2) * Sin(p_radlat2) > p_z2 = p_er * Cos(p_radlat2) > > p_d = Sqrt((p_x1 - p_x2)^2 + (p_y1 - p_y2)^2 + (p_z1 - p_z2)^2) > >***Side, side, side, law of cosines and arccos > p_theta = Acos(((p_er^2 * 2) - (p_d^2)) / (p_er^2 * 2)) > >***These need to be rounded > p_dist2 = p_theta * p_er && Distance in Kilometers > p_dist3 = p_dist2 / 1.609344 && Distance in Miles > p_dist4 = p_dist2 / 1.852 && Distance in Nautical Miles > > Set Decimals To &p_svdec > > Do Case > Case p_type = 0 > Return p_dist > Case p_type = 1 > Return p_dist3 > Case p_type = 2 > Return p_dist2 > Endcase > > Return p_dist > > >