** Next:** Initial and boundary conditions
** Up:** POINT SOURCE
** Previous:** POINT SOURCE

Let us assume the location of the point source is *x*_{0} on the surface.
With the coordinate transformation:
| |
(3) |

we can derive the orthogonal equation in the polar coordinates:
| |
(4) |

where and . The function *p* has a
physical meaning of surface horizontal slowness:
| |
(5) |

where *s*_{0} is the slowness at the source location, is the angle
between incident ray at the surface and the vertical.
Along each ray, the surface horizontal slowness *p* maintains to be constant.
Therefore, we can trace a ray by following the trajectory
of a contour line of *p*.

** Next:** Initial and boundary conditions
** Up:** POINT SOURCE
** Previous:** POINT SOURCE
Stanford Exploration Project

12/18/1997