<div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> You can't use any published map sources that you<br>consider reliable as it is too new for o-o-cop maps.
<br>Any thoughts?<br></blockquote></div><br>I guess the options are persuade the designers/contractor to
provide a drawing or other data, that can be used, or getting out the
theodolite. For a slightly less accurate approach (afterall, I hope
nobody is going to try and do any groundworks based on our data - so
who cares), you could try taking bearings with a compass at regular
intervals. It might depend on how the tunnel is lined whether the
compass works. Blackadder might know.