NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Ratiometer
From: Michael Dorl
Date: 2011 Feb 09, 07:57 -0600
From: Michael Dorl
Date: 2011 Feb 09, 07:57 -0600
On 2/8/2011 8:51 PM, Gary LaPook wrote: > > This guy purchased a "ratiometer" can any of you figure out what it is? > > http://www.chaski.org/homemachinist/viewtopic.php?f=15&t=89030 > > gl > > > ---------------------------------------------------------------- > NavList message boards and member settings: www.fer3.com/NavList > Members may optionally receive posts by email. > To cancel email delivery, send a message to NoMail[at]fer3.com > ---------------------------------------------------------------- > Well, it could be used to compute horizontal distances given line of sight distances taken at some angle to the horizontal. For example in rough surveying using stadia distance measurements. Also as I remember my surveying class some 55 yrs ago, there was a tedious method for computing the area enclosed by a polygon involving what were called Latiudes and Departures, the length of projections of a polygon side on the X and Y axis. The ratiometer could certainly help with that given the bearings of the sides. Say a segment ran at a bearing of 30 degrees and was 455 feet long. You set the movable arm to the requisite angle, move the slide so that touches .455 on the arm, and read off the latitude and departure on the scales. No multiplication needed. All you have to do is keep track of the decimal point but engineers in the slide rule era were good at that. But neither of these explains the needle points. :-( Quite a collection the fellow has! Mike