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Total Station VS Auto / Digital Level for height "stakeout"  


Bojan Petkovic
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Dear all,

just wondering what is your opinion for accuracy when we mark elevations with total stations versus level instruments... I have construction site with Benchmarks established each 100 m. The accuracy of this Benchmarks is good - each TS resection is under 2 mm. We stake (mark levels) in these 100 meters.

I would like to use TS for all marking but a bit afraid of accuracy, so at this moment we are using TS for alignment and for the level marking Auto level instrument that is time-consuming.

Note that we have by Quality standard +- 5mm

Thank you in advance

 

 

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Bill93
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A digital level would be the most accurate and fastest.  An auto level next best. Refraction and curvature correction would be useful if sights are not approximately balanced, but should be well within you tolerance.

It can be done with the total station, but unless sight lengths are balanced you probably need to average face 1 and face 2 readings for each point and that will take a bit longer.  

If the TS is robotic and following a prism, don't use a 360 degree prism, as that would give more vertical uncertainty.

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Bojan Petkovic
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@bill93

Hi and tnx for fast comment. We are using Robotic TS but on small prism (Leica TS16 + small prism +17.5 constant) - my plan was to use 3D polylines and surfaces for stakeout so we would speed up process multiple times...

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Jim Frame
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+/-5mm relative or absolute accuracy? 

For run-of-the-mill civil infrastructure, I wouldn't even think about using a level to set construction stakes anymore -- it takes to much time and returns, at best, a negligible increase in accuracy.  (That said, I don't do much construction layout these days as a matter of choice.)

Unless this is a project requiring an unusual degree of accuracy, a total station in good adjustment coupled with sound field practices will provide more than adequate results.

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Bojan Petkovic
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Hi Jim,

I would say relative accuracy to the closest benchmarks because we will work in this 100 meters (distance between benchmarks). We are doing road /utility reconstruction...

My original plan is to use cad lines and surfaces as I have this on disposal so no additional data need to be calculated and it will reduce time multiple...

I forget to mention the project is in Qatar - Middle East ...

Bojan

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party chef
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Total station should be fine, do your resections in two faces to button up the HI a little and be sure the equipment is in good working order. I would consider starting early in the day and using an umbrella as well. One approach is moving often to be close to the work and using reflectorless or a sheetprism along with red laser to get the chainman close, this is assuming a two person crew and fixed control points that do not need to be visited for every set up. 

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