I was set to go through my field notes and reduce some sets of angles when it dawned on me that I'm not sure (yeah I know, this oughta' be good) what I had learned in this regard is a correct application of the fundamentals. I had typically taken the mean of my foresights and then applied the mean excess or deficiency in my backsight to the foresight mean.
I'm not sure whether I am applying a correct methodology, or if the method would differ depending on the circumstances (i.e. type of instrument, least count of the micrometer)
This has me contemplating the theory of turning sets, and the rationale behind the adjustments to apply.
Advancements in industrial technology has produced instruments rated at <01", and given that state of rated accuracy its maybe not that hard to assume the two axis of the instruments hold a perpendicular relationship that meet or exceed this rating.
If I apply this perpendicular relationship to the theory of turning sets I am lost to understand why exactly it is the mean of two sightings is the correction, other than it is the most reasonable, or equitable distribution.
From my understanding, if the two axis hold a true perpendicular relationship, then a reverse sight on the operational plane would bisect the gravitational plane at exactly the same point.
If this understanding holds true, then I am correcting not so much instrument error than sighting errors ?
I guess if I had one question it would be, where could I find some reading material on the fundamentals of this operation.
You could add to that instruments more recently come with tilt compensators. Getting setup within less than 10" of level has got to give the instrument a fighting chance of remaining in the level pane. And I'm not sure how, and not to get any more confused, but I had just read a brochure recently for an instrument claiming it maintained quadruple axis compensation. Where do they get two more axis from?
Man! I'm not exactly sure if that is even understandable.
If the perpendicular relationship of the two axis holds, then a reverse sight on the operational ellipse would bisect the gravitational(?)(level) plane at exactly the same instance ?
A typical Set:
BS F1 000-00-00
BS F2 180-00-10
BS M=00-00-05
FS F1 045-00-05
FS F2 225-00-25
FS M=45-00-15
<RT.=FS-BS=45-00-10
Sometimes it is done like this:
FS F1-BS F1=45-00-05
FS F2-BS F2=45-00-15
Therefore M=<RT.=45-00-10
Thanks, Dave. I know where I lost the perspective now.
"if the two axis hold a true perpendicular relationship, then a reverse sight on the operational plane would bisect the gravitational plane at exactly the same point."
I have no idea how I got that idea into my head.
The F&R angles only bisect at the instrument's plane of tilt. Man! I need a few more brain cells.
nearly normal makes his bl debut!!!
🙂
nearly normal makes his bl debut!!!
The air is thick with highly angular meteors.
You Mean Your Observed Angles
Don't throw anything else into the mix.
Paul in PA
Meaning Multiple Angles - Sure Could Use Some Quick Advice
If I hand you a quick set could you mean it - just so i'm not losing my brain here.
BS DIRECT: 000-00-00
FS DIRECT: 13-02-03
FS REVERSE: 193-01-59
BS REVERSE: 179-59-57
Thanks. there might be one bright spot in my day if I haven't lost this.
Meaning Multiple Angles - Sure Could Use Some Quick Advice
> If I hand you a quick set could you mean it - just so i'm not losing my brain here.
>
>
> BS DIRECT: 000-00-00
> FS DIRECT: 13-02-03
> FS REVERSE: 193-01-59
> BS REVERSE: 179-59-57
Actually, this would be better referred to as "reducing" the set since the mean of directions face left and face right is usually considered to be one observed direction.
[pre]
D R Mean Reduced
BS 0-00-00 179-59-57 0-00-58.5 0-00-00.0
FS 13-02-03 193-01-59 13-02-01.0 13-02-02.5
[/pre]
So the angle measured was 13-02-02.5
Meaning Multiple Angles - Sure Could Use Some Quick Advice
Kent,
Thank you for the quick reply. I was entertaining some real simple doubts after a traverse closure of over 1:3^6
Everything that could go wrong today did so. Got beat doing research and for some reason Carlson has decided in two successive traverses that one traverse closes on the actual closing point, and the second traverse has some different idea of what a closing point actually is..??
There's just some days I'm thankful for just an instrument and a calculator.
Meaning Multiple Angles - Sure Could Use Some Quick Advice
> Thank you for the quick reply.
Actually, it was a bit too quick. The answer was right, but the intermediate step was incorrect. What I should have posted was:
[pre]
D R Mean Reduced
BS 0-00-00 179-59-57 359-59-58.5 0-00-00.0
FS 13-02-03 193-01-59 13-02-01.0 13-02-02.5
[/pre]
So the angle measured was (still) 13-02-02.5
