EARTH_RADIUS = 6378137.0; //单位M function getRad(d: Double): Double; begin Result := d * PI / 180.0; end; function GetFlatternDistance(lat1, lng1, lat2, lng2: Double): Double; var f, g, l: Double; sg, sl, sf: Double; s, c, w, r, d, h1, h2: Double; a, fl: Double; begin f := getRad((lat1 + lat2)/2); g := getRad((lat1 - lat2)/2); l := getRad((lng1 - lng2)/2); sg := sin(g); sl := sin(l); sf := sin(f); a := EARTH_RADIUS; fl := 1/298.257; sg := sg*sg; sl := sl*sl; sf := sf*sf; s := sg*(1-sl) + (1-sf)*sl; c := (1-sg)*(1-sl) + sf*sl; w := ArcTan(sqrt(s/c)); r := sqrt(s*c)/w; d := 2 * w * a; h1 := (3*r -1)/2/c; h2 := (3*r +1)/2/s; Result := d*(1 + fl*(h1*sf*(1-sg) - h2*(1-sf)*sg)); end;
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