I was taught back in the deflection angle era that when you double angles you backsight-forsight-plunge-backsight-forsite. Until recently I kept up this habit, now I backsight direct; backsight reverse; forsight direct; forsight reverse. What does everyone else do?
backsight-forsight-plunge-backsight-forsite
backsight direct-plunge-backsight reversed
foresight direct-plunge-foresight reversed
Backsight-angle right to Foresight
Foresight-angle right to Backsight
Plunge
Backsight-angle right to Foresight
Foresight-angle right to Backsight
Loyal
What? No one breaks the bottom plate?
Doh! Did I just date myself?:-O
Miguel A. Escobar, RPLS, LSLS
sight the BS, unlock upper plate and turn an angle to the right to the FS and lock, unlock the lower plate reverse the gun and re-sight the BS using the lower plate then use the upper plate to turn an angle to the RT to the FS, divide the result by 2, should match the first angle turned on the upper plate, if you did it right. I turn sets differently.
jud
Must have the same robot as me. To heck with all that walking/driving back & forth, results are the same. Plus I'd need to buy another prism.
> I was taught back in the deflection angle era that when you double angles you backsight-forsight-plunge-backsight-forsite. Until recently I kept up this habit, now I backsight direct; backsight reverse; forsight direct; forsight reverse. What does everyone else do?
That is double-centering, not doubling angles. Doubling an angle (or accumulating angles) has nothing to do with plunging the scope.
Stephen
Ditto what Loyal does.
That is a set that closes the horizon, a good method especially with multiple fore-sights.
jud
I multiply by 2.
duhh.
I like to tell everyone I double angles, but actually not do it.
Just to be more clear, doubling an angle means just that, you measure an angle of, say 80° and then unlock the lower plate and put that reading at the backsite. Then you unlock the upper plate and turn to your front site again. You should be reading around 160°. That is Doubling and Angle. Divide by two to get an averaged, more precise angle. Better yet, repeat this step two more times and divide by 4. This is why I prefer the term "accumulating angles", exact same thing as doubling, only you don't stop at twice measured, you keep going as much as you like. It requires a repeating theodolite, which most are these days, albeit only electronically. No flopping of the scope is needed. Not that flopping scope isn't a good thing, it is. But again, it has nothing to do with doubling angles.
Stephen
> I multiply by 2.
>
> duhh.
After years of doing it bs --> fs direct, then bs --> fs reversed, I've changed my ways.
Now it's
Backsight direct --> foresight direct.........foresight reversed --> backsight reversed
I just started doing this after it started making sense to me. It's just reading a single encoded plate. The closer in time you can turn the angles, the less time there is for the instrument to drift. The less you rotate the head, the less drift there is. The less you are walking around the tripod...you get the idea.
I think this is much easier and should lead to tighter angles. That's my new theory anyway.
If someone can educate me as to why this is not a good idea with a modern instrument, please do.
JRL
Multiple tripods...3 man crew...
bs #21 occupy #22 fs #23
F1 BS - F1 FS record zenith angle and distance
F2 FS record zenith angle and distance - F2 BS
bs #23 occupy #22 fs #21
F1 BS - F1 FS record zenith angle and distance
F2 FS record zenith angle and distance - F2 BS
repeat with different parts of the plate...
takes care of collimation, closes the horizon, reciprocal zeniths, and double checks the distances...and if you work it right, a closed loop from a 'dog-leg' traverse.
DDSM
(T-2 and Distomat DI-10 recorded in a field book)
Backsight direct --> foresight direct.........foresight reversed --> backsight reversed
That's me!
Perry How do you like to double angles
Perry,
you are wicked
With dc
Bs, fs, flip, bs, fs
Without dc
Bs, fs, release lower motion (or hit hold on my digital guns), bs, lock lower motion, fs
What can I say, I was taught the old way. My robot doesn't care and neither does Tds about breaking the plate.
Same. I use the default TDS automatic rep. routine. I think it even says in the manual that the default, BS-FS-FSREV-BSREV is the fastest way to do it.
