Re: Total Station or 3D Laser Scanning?

Yuk! Sounds like the job from hell!
I don't think I would have even bothered quoting for that one.

I've no experience with laser scanners - they might be the right tool for
the job if you can position it above the surface, but you'd have to get hold
of one with a resolution of 1mm to be sure of getting your 3mm accuracy -
not sure if that is possible or cost effective, but like I said, I'm no
expert & I could be wrong.

As for using a total station:
You will be trying to achieve something that is going to be very difficult
and very unneccessary. It is very difficult to hold a mini prism on the
exact corner of even a precision cut slab - then you've got the instrument
accuracy on top of that. You'll get 3mm on a lot of your points if you have
the right kit & take great care, but a of a lot of those 28000 points will
be out of tolerance I expect.

I'd go back to the client & suggest that you produce a schematic plan of the
surface showing all the slabs & cobbles - they may even have a design
drawing with them all on already. I'd then go around with the client &
hi-light the real problem areas (I doubt if all 7000 slabs & cobbles are
wrong). Create a DTM surveyed with a total station to show high / low
spots - I'd use a robotic / Autolock instrument for speed. You can always
survey areas that are particulary bad in greater detail/accuracy once they
are identified.
If you need to check slab sizes - use a tape measure. It's easy to use &
easy to measure to +/- 3mm. Mark these sizes on the schematic drawing. A
careful visual inspection will show any steps between adjacent slabs - again
these can be marked on the drawing.

What ever you decide to do, good luck - you'll probably need it!



--
Kind regards
Steve Bury

Bury Associates Limited
www.buryassociates.co.uk
T. 01905 26222
F. 01905 22555
"Stu" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hi,
>
> My company has recently won a contract to survey as-built positions
> and levels of granite slabs and cobbles in a 60m x 40m indoor area. We
> are required to survey all slab corners and individual cobbles ( a
> total of 28,000 points) to an accuracy of +/- 3mm. The client is
> hoping to make a claim against the flooring contractor for being out
> of spec, trip hazards etc.
> I was originally going to survey it conventionally with total station
> and prism, but I have been thinking about other solutions. Would laser
> scanning be a viable alternative? Would laser scanning give the
> required accuracy? The survey was priced for about 3 weeks field time
> and 1 week office.
>
> Any advice gratefully received.
>
> S. Thomas
> Geomatics Manager