expoweb/handbook/survey/ontop.htm

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<title>CUCC Austria Cave Surveying Guide: Surface</title>
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<h2 align=center>CUCC Expedition Handbook: Surveying<br>
Surface surveys</h2>
<p>All features of speleological interest should be recorded with a minimum
of two bearings on fixed landmarks (see <a href="../findit.htm">separate
document</a> for pictures of the various peaks we use). However, anything
which gets a number should eventually be linked into an existing Surface
Survey. The number (on a metal tag) will eventually be attached to the cave
entrance with a bolt, so it is useful to drill a hole for this (and place the
spit if possible) early on, so you can use that point as the start of the
underground or surface surveys. If possible, it helps to fix new stuff with a
GPS (use waypoint averaging for a couple of hours whilst you explore it).
There is a separate manual document for <a href="gps.htm">using GPS on
expo</a>.
<p><a href="../../piclinks/ssvypl.htm"><img src="../../tinypix/ssvypl.jpg"
width=122 height=122 hspace=10 align=left></a>
<p>The main difference with a surface survey is that you can see, and are not
constrained by passage walls. The lack of walls may mean that all survey
points are on the floor, which can be a pain. It is useful to use one or two
"survey staffs", which may be as simple as a stick shoved in a grike, or a
photographic tripod which is handy. Make sure not to place a compass too near
anything made of steel ! An aluminium pole (old tent pole, ski stick or any
odd bit of tube or angle) is light and effective. Making it a useful length
(eg. 1m or 1.5m) means it can double as a ruler for measuring features.
Surface survey legs tend to be longer than underground ones, so errors from
poor compass/clino readings are bigger. In good light you may find it easier
or get more consistent results by sighting the compass with <b>one</b> eye
rather than two. Remember to do this consistently, and use the same method
when doing your calibration. For better accuracy, you should really keep the
survey legs short (6m gives a compass/clino error comparable with a 5cm
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station position error). This makes the survey take much longer, and maybe
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more prone to recording errors, so a good compromise is to keep legs down to
15m or less, which also makes sketching a little easier.
<p><b>Don't neglect sketching&nbsp;!</b> Cold, exhaustion and call-out times
should not be such a restriction on surface surveys, so don't do a rush job
(it is best <b>not</b> to do surface surveys when the weather is awful:-).
A good surface sketch makes caves easier to find, possibly saving future
cavers from repeating your bearings to find the entrance. Eventually such
sketches will build to a map of the area, showing which bits have really been
looked at. It is conventional to survey to the cave marker tag, where there
is one (and you could always drill a spit for one, and survey to it). Failing
that, the centre of the painted number or middle of the "+" sign, or the
first bolt of the rigging (remember that we are no longer allowed to paint
marks on the plateau surface). Make sure that you record what is used, and
its height above/below the "surface".
<p>If you do run out of time, make sure that your final survey point can
readily be found again, for example a drilled hole in a prominent boulder
(take a photo). Consider going back a few legs if it will give you an
easier to find end point - better to lose one or two legs than have to redo
the whole survey !
<h3>Finding a starting point</h3>
<p>If your new cave is near a well-documented one, then a short connecting
survey from one to the other is straightforward. The point on the cave
should always be accessible without caving gear. Usually this will be the
cave marker tag (or the spit you have placed for one, or hole drilled for
it). If there is just a hole, it is as well to mark it with a bit of paint
so it can be found again. Failing these, a well-documented spot which can
be found again is essential - the first bolt of the rigging or part of a
painted number.
<p>The surface is now becoming laced with a network of surface surveys of
different vintages and qualities. As these build up, good sketching means
a useful scale map can be drawn, which in turn means you can look to see
where the nearest existing fixed points are to your cave. The best fixed
points are the ones fixed by accurate (laser theodolite) survey by the
Austrians, commonly known as <a href="lasers.htm">"laser points"</a>. Next
best are surface surveys taking a short route from these points.
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<b>Expedition Handbook</b>:<br>
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<b>Surveying</b>:<br>
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<a href="index.htm">Back to overview</a> and index of topics<br>
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<a href="what.htm">What is a cave survey ?</a><br>
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Methods: <a href="how.htm">underground</a><br>
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Pitfalls to avoid, <a href="hints.htm">hints'n'tips</a>
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