hi,i m Reza and i would like to know  how many error traverse at a tunnel and what is best the way?

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Hello Reza,

I think you're going to get more response to your post if you provide some more information.

I don't have much true tunnel experience, but the basic principles of control in a tunnel are not different than those in any situation where optimum geometry or strength of figure is not available.

In the worst of all situations, you have only a long open traverse ... even if you run alternating control stations and create triangles, you're going to end up with a weak figure that can do no better but propagate the error inherent in the equipment and care you put in.

Generally, transferring the "line" or azimuth of the survey below ground is the largest source of error. I'm imagining a shaft which typically doesn't give you much of a backsight when you get below ground. In a good situation, you can ask for a shaft further down the tunnel or co-opt an existing shaft and create a much stronger tie to the below-ground survey.

If you just generate coordinates from point to point, without any analysis of error, you're not going to know the uncertainty you've accumulated as you progress down the tunnel. There are many least squares adjustment programs that will take advantage of any redundancy you build into your survey and provide you a statistical analysis of a realistic certainty of positional tolerance. I prefer StarNet ... but use something.

Provide some more information or a more specific request and I'm sure someone here will pipe in with advice.

Tunnel surveying involves a lot of specific logistics, like spads (control hung on the ceiling) and special rigs for instrument setups and transfer of control. I suggest you seek a surveyor with specific experience to guide you in the early phases of your project setup.

Hello Rich Maher
with thank and apprecate you for your reply
i think
Considering that the drilling is done after both sides should be high precision operations and the creation of personal error must be avoided and the most important issue determining the coordinates of each point must be independent and multi-point control of transmission errors to be done to a point Another point to prevent the error amount in a tunnel traversing the same ground should be
Often guide holes are drilled and surface control plumbed down.  In the tunnel itself control is usually transfered to the ceilings or walls, because the floor is constantly being scraped and dumped on.
the key is support. Well-defined bases. These bases are placed in the rock, and so that it can putthe total station. Ceiling support points are crucial. Great care inputs and outputs of the curves.Review often traverse the support and confirm each week. But the autocad help much, but be careful.


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