Re: Orientation format

Jim Varney (
Wed, 14 Aug 1996 22:33:31 -0700

Walter Nissen wrote:

>I have made some important changes in the details of the format which I 
>propose for reporting orientation (of tethers).  

>I suggest this convention.  Assume that the observer is able to 
>distinguish Ralph from Norton.  If the orientation is, e.g.: 
>then the vertex angle is: 
>and the observer should report a vertex angle between 0 and 359.99 
>degrees.  I.e., the vertex angle (see appendix) of Norton with respect to 
>Ralph, i.e, the angle measured counter-clockwise from directly above. 
>If the observer cannot distinguish Ralph from Norton, then the angle reported 
>should be a vertex angle, determined in the same way, between 0 and 179.99 

My personal opinion is that the "20 degrees Lower Mass Leading" convention
is preferred.  It abbreviates to a short, elegant "20 deg LML."  I also
like the "LML" or "LMF" format because it translates very naturally from
what we actually observe -- deviation from apparent vertical.  

Vertex angle is usually not measured from the apparent vertical.  To create a
new definition of vertex angle with a different coordinate reference might 
introduce confusion.

In the engineering world the term for deviation from vertical is "slope."
A vertical slope is a 90 degree slope; so 20 deg LML would be reported as
70 deg, while 20 LMF would be noted as 110 degrees.  This would work,
but it seems awkward in comparison to the "LML" convention.

 -- Jim

Jim Varney      |  121^ 23' 54" W,  38^ 27' 28" N   |           Sacramento, CA
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