I'm working on a 5km long highway corridor project where we are building a series of new bridges, viaducts and retaining walls in order to 4 lane and remove the old existing two lane highway through a mountain pass in the Rockies.
The issue we're facing is any ground surface is at a premium, it's either used for parking or is continually being work over by earth works. It's turned into a cat and mouse game of resetting control and it being destroyed. To make things worse, they've opened the highway full time so we can no longer access our control on the edge of the road.
Besides setting rebar in the ground down low (with very poor sight lines), as structures get built there are area of concrete that are available, steel beams and piles, and rock face. The rock however is very crumbly and slides non-stop.
I've attached a few pictures to give you an idea of the terrain.
I had an idea of making a forced centering plate out of 5" x 5" x 1//4" steel plate, drilling holes into it to mount it via anchor bolts to concrete with spacers to keep it off the concrete surface and welding a 5/8" bolt through the middle to screw on a prism holder (pics attached as well). This could be placed on concrete structures and welded onto steel beams or rock retention wall posts.
Anyone have any other ideas or tried something similar??ÿ
How about establishing some targets on the rock face across the road and resecting instrument positions as needed??ÿ
The redneck version might be to saturate the rock face with many somethings like a PK nail or a flat brassie drilled in and epoxied and do reflectorless control in vertical faces.
Laser on a paint spot has the fewest moving parts. No hardware required.
?ÿ
Some of that epoxy fridge paint and maybe the gold paint pen this time.
?ÿ
Ooof!?ÿ What a great challenge to maintain your control.?ÿ ?ÿYou have a neat solution as long as the pieces your attached to don't move or shift i.e. jersey barrier etc.
Thanks for the photos.?ÿ This will be useful for planning purposes if I?ÿ ever get faced with similar issues and will introduce them for the design engineer team to allow for the inclusion of locations that can be created to allow control to be transferred from and perpetuated for efficiency and consistency.?ÿ
How about establishing some targets on the rock face across the road and resecting instrument positions as needed??ÿ
The problem I see with using RL on this project is most of the time I'd be looking at a pretty oblique angle on the targets since it's a corridor. Obviously I want to be perpendicular to targets when shooting RL and that just won't happen on a long, narrow project like this. The vast majority of the site is 20m wide, the one image of the big open area with the ravine is the exception.
?ÿ
The Trimble's were using don't seem to be as accurate as Leica's in RL as well. I believe they have a wider beam?
How about establishing some targets on the rock face across the road and resecting instrument positions as needed??ÿ
The problem I see with using RL on this project is most of the time I'd be looking at a pretty oblique angle on the targets since it's a corridor. Obviously I want to be perpendicular to targets when shooting RL and that just won't happen on a long, narrow project like this. The vast majority of the site is 20m wide, the one image of the big open area with the ravine is the exception.
?ÿ
The Trimble's were using don't seem to be as accurate as Leica's in RL as well. I believe they have a wider beam?
Yes, Trimble beams are a bit wider than Leica making RL less effective on small targets. You still want to avoid oblique angles if you can, especially if you are moving around a lot.
I'd look at using these targets:
on the rock face and on permanent structures as they are built. I've used them several times before, just bolt or epoxy to whatever surface you like.
I really like placing them in pairs, one lower, and the other one as far up as I can get it. Dials in the resections a bit better, especially the vertical. If you can see any two of those pairs you ought to be good to go.
I looked at the link and didn't readily find a spec on the distance between the centers of the two faces. Seems like that would be important.
You can actually purchase the forced centering plates which may be cheaper than fabricating them yourself.?ÿ you could use the same for a backsight or drill in monitoring targets (small circular prims on an 'L' bracket) high on a rock face.?ÿ Try Seco or Omi for both.?ÿ On a project like this, why spend the time climbing around setting reflectorless targets when you can set something a little more precise.?ÿ The other advantage of monitoring prisms is that you can have the instrument check them robotically.
The problem I see with using RL on this project is most of the time I'd be looking at a pretty oblique angle on the targets since it's a corridor.....
Then simply establish control nails - about every 100 metres or so - just on the traffic side of the of the jersey barriers that you can lean over to reach, and resect to those as needed. I'd suggest putting nails or marks in the barrier itself but I'd be concerned about the barrier moving.?ÿ ?ÿ?ÿ
Another idea is to rely more on RTK to do your layout.?ÿ
How about establishing some targets on the rock face across the road and resecting instrument positions as needed??ÿ
The problem I see with using RL on this project is most of the time I'd be looking at a pretty oblique angle on the targets since it's a corridor. Obviously I want to be perpendicular to targets when shooting RL and that just won't happen on a long, narrow project like this. The vast majority of the site is 20m wide, the one image of the big open area with the ravine is the exception.
?ÿ
The Trimble's were using don't seem to be as accurate as Leica's in RL as well. I believe they have a wider beam?
Yes, Trimble beams are a bit wider than Leica making RL less effective on small targets. You still want to avoid oblique angles if you can, especially if you are moving around a lot.
I'd look at using these targets:
on the rock face and on permanent structures as they are built. I've used them several times before, just bolt or epoxy to whatever surface you like.
I really like placing them in pairs, one lower, and the other one as far up as I can get it. Dials in the resections a bit better, especially the vertical. If you can see any two of those pairs you ought to be good to go.
These look fantastic. You've used these? Any idea at what distance the beam of RL would start causing issues? Either spilling over the sides of the fixed targets or hitting the arms of the swivel targets?
You can actually purchase the forced centering plates which may be cheaper than fabricating them yourself.?ÿ you could use the same for a backsight or drill in monitoring targets (small circular prims on an 'L' bracket) high on a rock face.?ÿ Try Seco or Omi for both.?ÿ On a project like this, why spend the time climbing around setting reflectorless targets when you can set something a little more precise.?ÿ The other advantage of monitoring prisms is that you can have the instrument check them robotically.
I can't seem to find any when I google them, any idea where I could look specifically?
The problem I see with using RL on this project is most of the time I'd be looking at a pretty oblique angle on the targets since it's a corridor.....
Then simply establish control nails - about every 100 metres or so - just on the traffic side of the of the jersey barriers that you can lean over to reach, and resect to those as needed. I'd suggest putting nails or marks in the barrier itself but I'd be concerned about the barrier moving.?ÿ ?ÿ?ÿ
That's one thing we were doing until they fully opened the highway and banned (safety) us from walking on the downhill slope side of the barriers (without using fall protection which would take way too long) and we can't walk in the ditch or edge of the highway without calling traffic control and shutting the highway down which takes 45 minutes to set a backsight.
?ÿ
We use rtk for earthworks and rough layout, but there is a lot of work here where the accuracy or rtk isn't sufficient.
