How do you measure accurately building corners with a prism? Οf course with reflectorless is easy but with prisms?
This is a prism from a German company
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This looks like it is designed to get the building corner at the grade level.
I would think any pole/prism combination would work. Just use the hidden point offset routine in a data collector or manually calculate the corner.
No longer a question, with my AP20.
Okay, this may be a bit extreme but it works great.
@john-putnam yeah it’s a 40k setup…
I do not measure building corners. Haven’t for years. I get reflectorless shots on the walls and intersect the wall lines.
If, for some reason, I couldn’t then the AP20 would be my fall back. A real game changer, the AP20.
But if you don’t have reflectorless I very much doubt that the AP20 would be an option for you.
@johnymal Only if you are including the instrument. The AP20, pole and batteries were around 10K when I purchased mine. So far I would say it was well worth the price with just the day-to-day workflow. Then there are the tasks that would be all but impossible with one person, such as that in the photo.
The AP20, pole and batteries were around 10K when I purchased mine.
I paid about that for our second one. The first I got for a little over $6k. This tilt sensing thing is the biggest thing in data collection since reflectorless, maybe since data collectors. I wouldn't want to be without it, although I have to admit that it isn't all sunshine and roses.
AP20 Tilt Sensor
The good:
- It's not just a tilt sensor. It also automatically updates the rod height, eliminating rod height errors
- And more than that there is the target id feature, which eliminates hooking up to the backsight and shooting that 50 times.
- On to the tilt sensing - Allows the user to focus attention on things other than the level bubble and target height. I find that I have way fewer coding errors. And then there is the safety factor of.
- Snookered behind a pole, tree, or parked vehicle? Lean out from behind it and get the shot. I haven't done an offset shot in I can't remember when.
- Used with a range pole or two to extend the rod height it can be used to collect invert elevations in manholes to a degree of accuracy not otherwise possible.
- Allows one to easily get direct shots on vertical walls and under things, like parked cars.
- Topo production, in terms of number of shots, goes way up. Last week I collected 450 points in under 2 hours, did not miss a single one for any reason, including blockages. This was on a street loaded with parked cars and curbside street trees, signs, poles, etc. I'd say that 1000 points in a full day would be an average day.
The bad:
- Not quite precise enough for control & boundary work. Maybe. Others may disagree.
- Has to be re-configured each time it is used after not using it.
- You have to keep moving to keep the tilt sensing active, and it can be a bit recalcitrant about re-initializing the tilt sensing at times. I'm told (by the salesman) that when used with the new TS-20 total station it acquires initialization much easier and retains it far longer.
- It only works with the mated rod, which extends to only 7.0 feet. This is less of a problem than it might otherwise seem to be because of the abilty to tilt.
- Its one more set of batteries and one more thing to set up.
- There is the cost.
@norman-oklahoma Bingo. Shoot faces relectorless, compute the corners. I go old school if thats not an option.
Set a rough 5x5 or other offset from the corner using a tape. Tie the point and occupy it. Backsight control then turn parallel with building face, fine-tuning and checking your oldest by sighting a level rod held horizontal. Record your angle and measured offset. Do the same for the other observable face.
There are numerous variations on this theme, and I bet you've used them. These tricks need passed on as they are still useful...
The bad:
- Not quite precise enough for control & boundary work. Maybe. Others may disagree.
- Has to be re-configured each time it is used after not using it.
- You have to keep moving to keep the tilt sensing active, and it can be a bit recalcitrant about re-initializing the tilt sensing at times. I'm told (by the salesman) that when used with the new TS-20 total station it acquires initialization much easier and retains it far longer.
- It only works with the mated rod, which extends to only 7.0 feet. This is less of a problem than it might otherwise seem to be because of the abilty to tilt.
- Its one more set of batteries and one more thing to set up.
- There is the cost.
If you routinely use a rod and bipod for control, then I think it is more accurate. Leica has a white paper out that indicated the IMU is better at determining plumb when the tilt is less that 5 degrees. Unfortunately, if you are turning sets, you need to re-acquire a fix when you invert the instrument or shoot the backsight.
I'm not sure why you need to re-configure each time you use it. Mine hooks up flawlessly (most of the time). I actually wish there was a way to temporarily stop the CS from communicating with it (more on that later),
The movement thing is pretty typical of all IMUs, you need an occasional location fix to account for drift. I do think that Leica has it dialed a little tight on the AP20. It can be real finicky when you loose lock some times where as the GS18 is much more forgiving.
There are a couple of software bugs in Captivate that I Leica needs to work out. First, once you have connected to the AP20 the instrument looses it mind when you try to check the backsight. It holds the last AP20 HR, changes the prism type to circular and sets the measurement to manual vs ATR. You can easily change these, but it is a little frustrating. This is even the case if you turn the AP20 off, it only goes back to normal when the TS, CS and AP20 are restarted. Second, sets of angles occasionally freaks out hard when the AP20 is connected. I think it has to do with the height reading. The CS will just act like nothing is happening while you can see the instrument repeatedly shoot the prism with no HR info. It always seems to happen when you are away from the TS.
As for the batteries, it would have been nice if they used the same type as the CS20 and GS18. I'm carrying around at least four battery types and sometimes five if I have a GS16 in the mix.
How about with no prism?
Make a closed traverse of at least three points where the building corner is visible from each station.
Turn angles only to the building corner from each of the stations.
Where the rays intersect is the coordinate of the building corner.
Or with a zero offset prism.
Make a mark on the building corner, and aim the EDM theodlite at the mark.
Screw a zero offset adaptor onto the prism and have an assistant aim the prism.
Push the button to measure.
Done.
Historic boundaries and conservation efforts.
How do you measure accurately building corners with a prism?
Is this a trick question? I do a lot of as-built topos and locate a lot of building corners with a robotic total station and a Leica GMP-101 prism. The outside edge of the prism frame is 0.10' from the prism center, so I kiss the corner with the side of the prism frame and use a distance offset routine. Quick, easy, accurate. With the occasional exception due to unusual obstructions, I get the ground elevation of the corner at the same time. What's not to like?
Getting back to the OP, this Bohnenstingl seems to be a german manufacturer of overengineered solutions in search of a problem.
@norman-oklahoma "Getting back to the OP, this Bohnenstingl seems to be a german manufacturer of overengineered solutions in search of a problem."
What a great observation and it applies to our current county map checkers as well. "overengineered surveyors in search of a problem that only exists in their overengineered minds." We have even had red-lined comments demanding periods at the ends of monument descriptions.