PostGIS  2.4.9dev-r@@SVN_REVISION@@

## ◆ ptarray_arc_length_2d()

 double ptarray_arc_length_2d ( const POINTARRAY * pts )

Find the 2d length of the given POINTARRAY, using circular arc interpolation between each coordinate triple.

Length(A1, A2, A3, A4, A5) = Length(A1, A2, A3)+Length(A3, A4, A5)

Definition at line 1665 of file ptarray.c.

References getPoint2d_cp(), lw_arc_length(), lwerror(), and POINTARRAY::npoints.

Referenced by lwcircstring_length_2d().

1666 {
1667  double dist = 0.0;
1668  int i;
1669  const POINT2D *a1;
1670  const POINT2D *a2;
1671  const POINT2D *a3;
1672
1673  if ( pts->npoints % 2 != 1 )
1674  lwerror("arc point array with even number of points");
1675
1676  a1 = getPoint2d_cp(pts, 0);
1677
1678  for ( i=2; i < pts->npoints; i += 2 )
1679  {
1680  a2 = getPoint2d_cp(pts, i-1);
1681  a3 = getPoint2d_cp(pts, i);
1682  dist += lw_arc_length(a1, a2, a3);
1683  a1 = a3;
1684  }
1685  return dist;
1686 }
int npoints
Definition: liblwgeom.h:371
double lw_arc_length(const POINT2D *A1, const POINT2D *A2, const POINT2D *A3)
Returns the length of a circular arc segment.
Definition: lwalgorithm.c:118
const POINT2D * getPoint2d_cp(const POINTARRAY *pa, int n)
Returns a POINT2D pointer into the POINTARRAY serialized_ptlist, suitable for reading from...
Definition: lwgeom_api.c:373
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
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