Construction Site Control

You mean construction site control in the site itself? It will definitely be gone. Is there surrounding structures as well?

Normally I try when I run a traverse in the site (I know it will be gone), I try to set target (Those reflector sheets) on surrounding structures or permanent features so I can resect of them if need be and they will seldom be gone.

Things on the ground will always blocking you. The foreman may be nice or not to help you but just assume they will not.

Normally when you use the total station properly (reading both faces, being careful when you), your residuals will definitely be less than 0.02. (I use a 3s gun and sometimes a 1s gun)

Whats N&D and IPC?

Cheers,

Jan

I'm guessing N&D is nail and disc and IPC is an iron pin with a cap?

I prefer to set iron pins with caps. Usually around here the soil conservation laws require the contractor to install a silt fence around the site along the limit of disturbance. I usually set my construction control using 5/8" rebar about 24" long just outside the silt fence around the site. I sometimes set secondary control inside the site, but I assume it won't last long. As far as the 0.02' tolerance, I am the only surveyor here so I do everything myself. I may hold one or two lines and lay out all the tight tolerance stuff from those point(s). The looser control (usually +/-0.04') is perfectly fine for laying out curb, storm, sanitary, sidewalks, etc.

I like several offsite controls to start with, and onsite, I like to set rebar and caps. I currently am responsible for the layout of a new high school on a 68 acre site. We have a concrete monument set onsite, away from any area of disturbance. This point is the Gospel, as far as vertical is concerned, for the whole site. As far as horizontal, I like to set my rebar and caps near any sanitary or storm structures. The reason for this, is that while Mr dozer operator may not "notice" my basket with paint and flagging, he will always steer clear of the exposed structures. Well, almost always, but that is a different story.

Like everything it all starts with the proposal. The fee will be the least if we have a clean site. If we cannot see the building from the control, it will take longer and the fee will be higher. If our control is disturbed, it will take longer and the fee will be higher.
We have been setting rail road spike with drill holes outside of the site at key points for major layout. The last one was a fire station and we had RRs at the line outs of the major walls. There was random control elsewhere.
Fortunately we were recently underbid for some bridge layout projects. Who needs the headache when the schedule is full?

The side of the project we're currently working on has no surrounding structures, just an on-ramp to an expressway. N&D means nail and disc. IPC means iron pipe and cap, even though I think that's an inaccurate description. The plastic survey marker goes inside of the pipe. Should be iron pipe and plug (IPP). Actually, we use 1-1/4" aluminum chain link fence posts cut to a length of 18", so should be APP.

I like to set a couple of baselines surrounding the site, so that I can reset the control inside the site after it disappears. Control inside the site is usually sporadic and in a place I'm hopeful it won't be hit. I also try to set somewhere I can spin an angle to a point outside the site to check into. I always "pig pen", or "cage" any points I can, but it seems when I make the points obvious they are knocked out quicker. The best points in construction sites for me always either nails and discs, or x-cuts on permanent structures that will not be disturbed like stated above. The more options the better when it comes to construction staking, because without a doubt there will be equipment on at least two of the points.

Dan Patterson, post: 353468, member: 1179 wrote: I prefer to set iron pins with caps. Usually around here the soil conservation laws require the contractor to install a silt fence around the site along the limit of disturbance. I usually set my construction control using 5/8" rebar about 24" long just outside the silt fence around the site. I sometimes set secondary control inside the site, but I assume it won't last long.

Our crews follow this approach whenever possible. The silt fence requirement helps control from being destroyed, plus it provides a safe spot to set up the instrument. A long baseline is established soon as construction gets underway. We usually do the topo surveys too, so once design is finished, we use the initial control to set that baseline where it won't get damaged. 1/2"x24" rebar with plastic caps are our monument of choice for control. Anything that we know is temporary will be hub and tack.

...I usually set my construction control using 5/8" rebar about 24" long just outside the silt fence around the site....

You might consider that silt fence is more often on lower ground than higher ground. This being the case it will be subjected more to the influence of water, whether surface or subsurface water.

Water will saturate the ground causing swelling and heaving which moves your control. The ground will eventually dry out causing shrinking and subsidence which moves your control.

Construction control requires locating the control point in safe stable locations while the instrument needs to be located where the work can be accessed. Conventional control point occupation using a known a backsight often failed in the second objective. For a good number of years most lfield software contains a setup and orientation option by which the instrument can be set at a unknown location (chosen for usability). The position is calculated by least squares requiring a minimum of 3 up to 9 (with my current software). The requirements are the primary control be tight and the unknown setup point have a strong geometric relationship to the primary control (>30å¡ <150å¡ between measured pairs). We have our rejection spec set to <0.03-ft horizontal and <0.015-ft vertical. I can say this method has consistently held-up to staking audits for state/federal road and bridge layouts. We found that control deterioration was minimized on those multi year projects.

bridger48, post: 353774, member: 6251 wrote: Construction control requires locating the control point in safe stable locations while the instrument needs to be located where the work can be accessed. Conventional control point occupation using a known a backsight often failed in the second objective. For a good number of years most lfield software contains a setup and orientation option by which the instrument can be set at a unknown location (chosen for usability). The position is calculated by least squares requiring a minimum of 3 up to 9 (with my current software). The requirements are the primary control be tight and the unknown setup point have a strong geometric relationship to the primary control (>30å¡ <150å¡ between measured pairs). We have our rejection spec set to <0.03-ft horizontal and <0.015-ft vertical. I can say this method has consistently held-up to staking audits for state/federal road and bridge layouts. We found that control deterioration was minimized on those multi year projects.

Are you talking about a resection? I've had some recent work where those residuals wouldn't have worked. I found the best option was to use the same occupation point and backsight point for layout (which were carefully chosen outside the limit of disturbance in a location where the column line offsets would be visible). Checks were made to other control points always within 0.005' or less. I used to think that anything less than 0.01' was impossible or just lucky, but i managed to repeat the result every time over many months.

For pretty much all the other stakeout items, the resection with 0.03' residuals would be totally fine, but this particular building had crazy tolerances.