#include <cmath>
-#include "structure/exception.hxx"
+#include <simgear/structure/exception.hxx>
#include "SGMath.hxx"
// These are hard numbers from the WGS84 standard. DON'T MODIFY
#define E2 fabs(1 - _SQUASH*_SQUASH)
static double a = _EQURAD;
static double ra2 = 1/(_EQURAD*_EQURAD);
-static double e = sqrt(E2);
+//static double e = sqrt(E2);
static double e2 = E2;
static double e4 = E2*E2;
double Y = cart(1);
double Z = cart(2);
double XXpYY = X*X+Y*Y;
+ if( XXpYY + Z*Z < 25 ) {
+ // This function fails near the geocenter region, so catch that special case here.
+ // Define the innermost sphere of small radius as earth center and return the
+ // coordinates 0/0/-EQURAD. It may be any other place on geoide's surface,
+ // the Northpole, Hawaii or Wentorf. This one was easy to code ;-)
+ geod.setLongitudeRad( 0.0 );
+ geod.setLongitudeRad( 0.0 );
+ geod.setElevationM( -EQURAD );
+ return;
+ }
+
double sqrtXXpYY = sqrt(XXpYY);
double p = XXpYY*ra2;
double q = Z*Z*(1-e2)*ra2;
double r = 1/6.0*(p+q-e4);
double s = e4*p*q/(4*r*r*r);
+/*
+ s*(2+s) is negative for s = [-2..0]
+ slightly negative values for s due to floating point rounding errors
+ cause nan for sqrt(s*(2+s))
+ We can probably clamp the resulting parable to positive numbers
+*/
+ if( s >= -2.0 && s <= 0.0 )
+ s = 0.0;
double t = pow(1+s+sqrt(s*(2+s)), 1/3.0);
double u = r*(1+t+1/t);
double v = sqrt(u*u+e4*q);
double sinphi2 = sin(phi2), cosphi2 = cos(phi2);
if( (fabs(lat1-lat2) < testv &&
- ( fabs(lon1-lon2) < testv) || fabs(lat1-90.0) < testv ) )
+ ( fabs(lon1-lon2) < testv)) || (fabs(lat1-90.0) < testv ) )
{
// TWO STATIONS ARE IDENTICAL : SET DISTANCE & AZIMUTHS TO ZERO */
*az1 = 0.0; *az2 = 0.0; *s = 0.0;
}
double
-SGGeodesy::distanceM(const SGGeoc& from, const SGGeoc& to)
+SGGeodesy::distanceRad(const SGGeoc& from, const SGGeoc& to)
{
// d = 2*asin(sqrt((sin((lat1-lat2)/2))^2 +
// cos(lat1)*cos(lat2)*(sin((lon1-lon2)/2))^2))
double tmp2 = sin(0.5*(from.getLongitudeRad() - to.getLongitudeRad()));
double square = tmp1*tmp1 + cosLatFrom*cosLatTo*tmp2*tmp2;
double s = SGMiscd::min(sqrt(SGMiscd::max(square, 0)), 1);
- return 2 * asin(s) * SG_RAD_TO_NM * SG_NM_TO_METER;
+ return 2 * asin(s);
+}
+
+
+double
+SGGeodesy::distanceM(const SGGeoc& from, const SGGeoc& to)
+{
+ return distanceRad(from, to) * SG_RAD_TO_NM * SG_NM_TO_METER;
}