NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Measuring (and Calculating) Dip
From: Bruce J. Pennino
Date: 2013 Mar 11, 16:39 -0400
From: Bruce J. Pennino
Date: 2013 Mar 11, 16:39 -0400
Bruce
Paul:
For the American transit, I had vaguely remembered
that in the "ole days" there were procedures to flip the scope, turn angles
right, turn angles left etc. I never did any of these things because I've
never done highly precision work as required for a land survey, long distance
surveys, or legal documents. I'm a civil engineer that does very
simple / ordinary construction layout, mostly as a volunteer for Rail Trail
work. Once I bought an EDM/theodolite the precision and accuracy was so much
greater that specialized procedures became totally unnecessary for
me.
However, for measurement of small vertical
angles, technique becomes very important. My plan is
now to set up the theodolite, make a set of readings "wire" coming
down; another set wire going up. Flip "gun" 180*, rotate 180* and
redo. I honestly don't remember how my internal optical angle
scale functions in the "reversed" mode ie, whether the sign of the angles will be greater or less than the
previous mean value. Maybe doubled? I'll go read the manual and a good surveying book. Your comments are
appreciated and I think saved me some work while increasing precision and total
accuracy.
Regards
Bruce
----- Original Message -----From: Paul HiroseSent: Monday, March 11, 2013 11:17 AMSubject: [NavList] Re: Measuring (and Calculating) Dip
I wrote: > If you change faces, the effect > of index error has the same magnitude but opposite sign. Thus, the > difference of the face left and face right readings is the index error, > and the mean is free of index error. Correction: the difference between face left and face right is TWICE the index error. --: http://fer3.com/arc/m2.aspx?i=122772
