Detection of underground utilities (Pipes, cables etc)

I think you should ask this question in the Civil Engineering forum, not software and programming.

Tom

I use a combination of both Cable/pipe locator and a GPR scanner. This will give us almost precise results. What kind of precision are you looking for?

you man something like this?

http://www.gp-radar.com/groundsonar.htm

Google is easy

Have you considered Water Devining? I was initially sceptical because I havnt been able to find a scientific explanation of how it works. However I have recently mapped out the waste water pipe runs under my garden, using two 'L' shaped wires made from Coat Hangers,with sufficient precission to guide the JCB Digger that was digging them up.