×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

super accuracy positioning, precise levelling

super accuracy positioning, precise levelling

super accuracy positioning, precise levelling

(OP)
To measure top of a circular concrete pier 2m wide (inner diameter about 13m) about 1.5m up from datum point within 0.2mm on a grid of 150mm spacing (this will mean around 3000 points)

To test same for flatness deviation all round not to be more than +-0.5mm

To establish whether this "ring" is within 0.1 degree of horizontal.

This is then also connected to establish position to a nearby tower to within 0.5mm (distance around 30m further but much higher (I guess around 30m up)

Any suggestions as to methodology, precautions to be taken, and suggested instrumentation will be welcome. A bit of brainstorming on this would be welcome.

I propose to use a precise electronic level to get the levels to 0.2mm. What worries me is the positioning of the points on the pier (3000 of them) in plan (Y-X) to this same degree of accuracy or even 0.5mm. To this effect I envisage two single second total stations on a baseline within 1mm accuracy (EDM specs are 1mm plus 2ppm). The simultaneous intersection using such instruments (duly calibrated) should yield accuracies of this order as long as the baseline is around twice the diameter of ring.

I believe the site is also quite windy sometimes!

Any advice is welcome!

RE: super accuracy positioning, precise levelling

Hi,

I am a Kiwi surveyor with 11 years experience currently working in Singapore.

I suggest you contact Otago University in New Zealand who have in the past had to resolve such precise survey problems in their industrial engineering department which specialises in such high accuracy projects.

For a simple low cost solution your approach seems OK.

I have recently started using a 3D laser scanner from a company in france called mensi at www.mensi.com. They have 3D laser scanners that can measure to within 0.5 of a millimeter 100 points per second with their short range version. Although each measurement is slightly out of spec because you measure thousands of points in minutes the surface 3D model generated to far more accurate. No good for setting out but ideal for high accuracy as-built. We have one in singapore at www.hydronav.com.

Good luck

Allan Hosking
allanhosking@hotmail.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources