The early Sokisha total stations had a true lower motion with a clamp and fine motion screw.
Then in the early 90s the Sokkia total station I used had a lower clamp with a slide out guard but no fine motion screw which kind of makes you wonder why did they bother?
Everything I use now is directional, no lower motion. I think my Topcon GPT3005 can hold an angle on the display but that doesn't truly add up angles on the plate.
My Dietzgen 1' transit obviously can accumulate angles.
I don't double angles.
I turn sets, usually 4 which is 8 pointings (D&R). The motorized Leica 1200 with TDS Ranger does it automatically. It does BS D, BS R, FS R, FS D for one set. The automatic routine is pretty fast unless something gets in the way and upsets it then it takes several seconds to recover and try again. If we are looking down a road with potential cars in the way I turn off the automatic so I can tell it when to shoot.
We often close the horizon (which means 4 more sets), particularly on sideshots to found monuments or for other reasons. Sometimes I turn all the pieces of the pie if I have several foresights.
We have a lot of old field books. Deflection angles were very popular before the age of computers probably because it was easier to calculate the next bearing. They also noted compass bearings which makes it easier to figure out their notes (helps from time to time).
So, if I am reading this correctly, unless you have a lower motion you cannot turn double angles. Your electronic "hold" is merely holding a numerical value, not holding the plate inside.
Very interesting. I always thought I was turning double angles, but in practice was turning sets?
BTW, today I turn sets whichever way the last guy set the data collector.
I used to turn BS-FS, hold angle and plunge, BS-FS, zero, FS-BS, hold angle and plunge, FS-BS. Record angle at each reading (only really need accumulation) and divide accumulated angle. This is VERY fast. Sets in a data collector are much better, I think.
> So, if I am reading this correctly, unless you have a lower motion you cannot turn double angles. Your electronic "hold" is merely holding a numerical value, not holding the plate inside.
>
That is true, but unless you are surveying the world's biggest Swiss watch, today's instruments' cirlces don't need to have their different sectors read. They are pretty darn circular.
> Very interesting. I always thought I was turning double angles, but in practice was turning sets?
>
Yes.
> BTW, today I turn sets whichever way the last guy set the data collector.
>
> I used to turn BS-FS, hold angle and plunge, BS-FS, zero, FS-BS, hold angle and plunge, FS-BS. Record angle at each reading (only really need accumulation) and divide accumulated angle. This is VERY fast. Sets in a data collector are much better, I think.
Very fast and very good. That is all you need to do with today's instruments.
Stephen
I'd like some advice. I'm preparing to topo a long, narrow strip. Roughly 15000' x 300'. I've CAREFULLY set a pair, via VRS, at each end. Beginning at one end, I'm measuring 3 sets and 3 rounds (Trimble's multiple sets routine) to set control about every 500'. The plan is to close into the second pair at the other end and adjust as needed - assuming I'm close enough to feel confident that what I did is good. Here's the catch: as I move forward, I'm being asked to set some nails (sideshots) every 100' on a calculated baseline from a third party. No good, right? The nails I set won't really be ON the baseline, because I assume I'll have to make adjustments when I close to the second pair. The whole point of the adjustment is that I don't REALLY know where I am along the way, so how can I say that I'm on the baseline or not? Can't seem to get a consensus on this. I was told to double center to keep the line straight. How does that differ from what I'm doing (I don't think it does) and if it's different, how? And will it solve the problem? Will the nails be on the baseline?
Thanks.
The only problem with
"doubling" angles with a transit was the tendency (and I was guilty) to double the angle in your head and "force" the reading on the vernier to match what your head said it should be. I'd have to force myself NOT to double the angle in my head.
Modern day, BS direct, FS direct, BS inverted, FS inverted.
Andy
Here's the catch: as I move forward, I'm being asked to set some nails (sideshots) every 100' on a calculated baseline from a third party. No good, right? The nails I set won't really be ON the baseline, because I assume I'll have to make adjustments when I close to the second pair. The whole point of the adjustment is that I don't REALLY know where I am along the way, so how can I say that I'm on the baseline or not? Can't seem to get a consensus on this. I was told to double center to keep the line straight. How does that differ from what I'm doing (I don't think it does) and if it's different, how? And will it solve the problem? Will the nails be on the baseline?
>
> Thanks.
sounds right. if you wanted to be certain your new marks were on the baseline you would have to traverse, close and adjust first. on the return trip you stake your new marks. any other way is uncertain of the quality of the measurements and coordinates. we have done this both ways, you just have to answer the burning questions to yourself, is my work good enough? how 'good' does this baseline have to be? could i stake it on the way out, gamble on the quality and check in when i get in? might have to reset a couple on your way out, etc. hope it makes sense, ramble off.
