ptarray_length_spheroid()

double ptarray_length_spheroid	(	const POINTARRAY *	pa,
		const SPHEROID *	s
	)

Definition at line 3228 of file lwgeodetic.c.

References SPHEROID::a, SPHEROID::b, POINTARRAY::flags, FLAGS_GET_Z, geographic_point_init(), getPoint4d_p(), LW_FALSE, POINTARRAY::npoints, SPHEROID::radius, sphere_distance(), spheroid_distance(), POINT4D::x, POINT4D::y, and POINT4D::z.

Referenced by lwgeom_length_spheroid().

{
        GEOGRAPHIC_POINT a, b;
        double za = 0.0, zb = 0.0;
        POINT4D p;
        int i;
        int hasz = LW_FALSE;
        double length = 0.0;
        double seglength = 0.0;

        /* Return zero on non-sensical inputs */
        if ( ! pa || pa->npoints < 2 )
                return 0.0;

        /* See if we have a third dimension */
        hasz = FLAGS_GET_Z(pa->flags);

        /* Initialize first point */
        getPoint4d_p(pa, 0, &p);
        geographic_point_init(p.x, p.y, &a);
        if ( hasz )
                za = p.z;

        /* Loop and sum the length for each segment */
        for ( i = 1; i < pa->npoints; i++ )
        {
                seglength = 0.0;
                getPoint4d_p(pa, i, &p);
                geographic_point_init(p.x, p.y, &b);
                if ( hasz )
                        zb = p.z;

                /* Special sphere case */
                if ( s->a == s->b )
                        seglength = s->radius * sphere_distance(&a, &b);
                /* Spheroid case */
                else
                        seglength = spheroid_distance(&a, &b, s);

                /* Add in the vertical displacement if we're in 3D */
                if ( hasz )
                        seglength = sqrt( (zb-za)*(zb-za) + seglength*seglength );

                /* Add this segment length to the total */
                length += seglength;

                /* B gets incremented in the next loop, so we save the value here */
                a = b;
                za = zb;
        }
        return length;
}

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