Survey with laser instruments

[Wookey]

On 2008-07-15 08:53 +0100, Graham Mullan wrote:
> If I remember correctly, some years back work was done on the 
> theoretical constraints of surveying which showed that the optimum 
> length for a leg - in order to get the most accurate results - was 
> actually quite short, well under the length of a standard 30 m tape. 

About 7m IIRC due to relative innacuracy of compass/clino to tape.

> However, most surveyors will still go for the longest legs that they can 
> for speed, believing that their performance will not be affected so much 
> over shorter trips and thus accuracy will be maintained.
> 
> Has anyone done any similar work on surveying using laser tools rather 
> than tape and eyesight instruments and, if so, are the results any 
> different?

Not that I am aware of.

The nominal accuracy of the laser tapes is better than analogue tapes.
The nominal accuracy of the SAP is worse than compass/clino so in fact
the optimal leg length should be shorter - probably around 3m in
theory (handwave, no sums done). 

In practice (for most surveys) the biggest difference is much-reduced
opportunity for blunders, so overall significantly better results. On
the other hand tape errors will probably go up as it is easy to be
pointing it at slightly the wrong place and measure in front/behind.
Fortunately it is trivial to do them twice as a check.

Maybe we should force everyone to use the new, cheap laser tapes that
are software-limited to 20m :-)

Wookey
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