vertex angle, TiPS

Jay Respler (
Thu, 25 Jul 1996 23:31:26 -0400 (EDT)

I don't agree about the lack of agreement:

>There seems to be a lack of agreement between surveying and astronomy on 
>the name of the angle and the definition (see appendices).

>... vertex angle in occultation predictions ... is measured like 
>position angle, but 0 is the local vertical direction, rather than north. 
>Hence, 0 deg. is up, 90 is to the left, 180 is down, and 270 is to the 

The astronomy angle is one of rotation, counterclockwise from the top.

>Zenith Distance 
>The zenith distance is a vertical angle measured from directly overhead, down 
>to the required point.  An ideal horizon has a zenith distance of 90 degrees. 
>Vertical angle 
>The Vertical angle is the angle measured in a vertical plane, from the horizon 
>to the required point.  Directly overhead would have a vertical angle of 90

The survey angle just measures elevation.  It has nothing to do with rotation
or the apparent angle of Tips.

Jay Respler
Join us at Eurosom 2, the Satellite Observers Meeting: Oct.19/20, Belgium
Details of how to get on the Satellite Observer Mail List, satellite elements,
prediction programs and other satellite information, at the Visual Satellite
Observers Home Page:
--   or
     Satellite Tracker * Early Typewriter Collector
                Freehold, New Jersey