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<title>CUCC Expo Surveying Handbook: Surface surveys</title>
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2004-04-24 12:50:58 +01:00
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<h2 id="tophead">CUCC Expo Surveying Handbook</h2>
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<h1>Surface surveys</h1>
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<h3>Surface surveying is different</h3>
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<p>
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<a href="../../piclinks/ssvypl.htm"><img src="../../tinypix/ssvypl.jpg"
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width="122" height="122" alt="" class="onleft" /></a>
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The main difference with a surface survey is that you can see, and are not
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constrained by passage walls. The lack of walls may mean that all survey
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points are on the floor, which can be a pain. It is useful to use one or two
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"survey staffs", which may be as simple as a stick shoved in a grike, or a
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photographic tripod which is handy. Make sure not to place a compass too near
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anything made of steel! An aluminium pole (old tent pole, ski stick or any
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odd bit of tube or angle) is light and effective. Making it a useful length
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(eg. 1m or 1.5m) means it can double as a ruler for measuring features.
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<p>
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Surface survey legs tend to be longer than underground ones, so errors from
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poor compass/clino/distoX angle readings are bigger. In good light you may find it easier
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or get more consistent results by sighting the compass with <b>one</b> eye
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rather than two. Remember to do this consistently, and use the same method
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when doing your calibration. For better accuracy, you should really keep the
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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
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15m or less, which also makes sketching a little easier.</p>
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<p>Using a distoX above ground does make it hard to see the laser spot in bright
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sunlight of course, which limits the length of legs (except at dusk).
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<p><b>Don't neglect sketching!</b> Cold, exhaustion and call-out times should
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not be such a restriction on surface surveys, so don't do a rush job (it is
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best <b>not</b> to do surface surveys when the weather is awful:-). A good
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surface sketch makes caves easier to find, possibly saving future cavers from
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repeating your bearings to find the entrance. Eventually such sketches will
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build to a map of the area, showing which bits have really been looked at.
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<p>It
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is conventional to survey to the cave marker tag, where there is one (and you
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could always drill a spit for one, and survey to it). Failing that, the centre
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of the painted number or middle of the "+" sign, or the first bolt of the
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rigging (remember that we are no longer allowed to paint marks on the plateau
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surface). Make sure that you record what is used, and its height above/below
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the "surface".</p>
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<p>If you do run out of time, make sure that your final survey point can
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readily be found again, for example a drilled hole in a prominent boulder
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(take a photo). Consider going back a few legs if it will give you an
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easier to find end point - better to lose one or two legs than have to redo
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the whole survey!</p>
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<h3>Entrances and holes</h3>
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<p>All features of speleological interest should have their position recorded exactly.
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These days (2018) a long-average (200+ readings) GPS location is fine (see <a href="gps.htm">GPS for entrances</a>) in most parts of our caving area.
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This usually means using a handheld GPS device rather than a phone unless you have a particularly
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good GPS app which provides an averaging function.
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<p>If you are close to a big cliff, or almost inside an overhang, then an averaged-GPS will be good (~ 2m accuracy)
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for latitude/longitude but appallingly misleading for altitude. In some parts of our area, such as the steep cliffs of
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the Weisse Wand near Schnellzughöhle (as seen in <a href="../../piclinks/ssvypl.htm">the photo at the top of this page</a>),
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altitude is important for route-finding so GPS becomes surprisingly much less useful for re-finding locations. Before you use
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GPS you really should read <a href="gps.htm">GPS for entrances</a>.
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There is more about GPS altitudes in <a href="coord.htm">Olaf's article on GPS in Austria</a>.
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<p>Without GPS we need an old-fashioned survey location using fixed points
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with a minimum
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of two bearings on fixed landmarks (see <a href="../findit.htm">taking bearings
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</a> page for how to do this and for pictures of the various peaks we use).
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<p>Anything
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which gets a number (e.g. 2018-ad-01) should eventually be linked into an existing surface
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survey. The number (on a metal tag) will be attached to the cave
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entrance with a bolt, so it is useful to drill a hole for this (and place the
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spit if possible) early on, so you can use that point as the start of the
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underground or surface surveys. Always fix new stuff with a
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GPS (use waypoint averaging) as even if this is not full survey-quality it does prevent things getting lost.
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There is a separate manual page for <a href="gps.htm">using GPS for entrances</a>.</p>
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<h3>Finding a starting point</h3>
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<p>If your new cave is near a well-documented one, then a short connecting
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survey from one to the other is straightforward. The point on the cave
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should always be accessible without caving gear. Usually this will be the
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cave marker tag (or the spit you have placed for one, or hole drilled for
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it). If there is just a hole, it is as well to mark it with a bit of paint
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so it can be found again. Failing these, a well-documented spot which can
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be found again is essential - the first bolt of the rigging or part of a
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painted number.</p>
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<p>The surface is now becoming laced with a network of surface surveys of
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different vintages and qualities. As these build up, good sketching means
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a useful scale map can be drawn, which in turn means you can look to see
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where the nearest existing fixed points are to your cave. The best fixed
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points are the ones fixed by accurate (laser theodolite) survey by the
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Austrians, commonly known as <a href="lasers.htm">"laser points"</a>. Next
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best are surface surveys taking a short route from these points.</p>
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2004-04-22 21:43:17 +01:00
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<hr />
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<ul id="links">
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<li><b>Expedition Handbook:</b>
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<ul>
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<li>Expo Handbook <a href="../index.htm">Introduction</a></li>
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<li><b>Surveying:</b>
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<ul>
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<li>Surveying <a href="index.htm">Overview</a> and index of
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topics</li>
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<li><a href="what.htm">What is a cave survey?</a></li>
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<li><a href="why.htm">Why am I doing this?</a></li>
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<li>Methods: <a href="how.htm">underground</a></li>
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<li>Pitfalls to avoid, <a href="hints.htm">hints'n'tips</a> to
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make life easier</li>
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<li>Methods: surface</li>
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<li>A new cave: <a href="gps.htm">Getting a GPS fix</a></li>
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<li>Base Camp: <a href="getin.htm">getting it in</a> to the
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computer</li>
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<li>Base Camp: <a href="drawup.htm">drawing it up</a>, writing
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the description</li>
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</ul></li>
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<li><a href="../look4.htm">Prospecting guide</a></li>
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<li><a href="../rescue.htm">Rescue guide</a></li>
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<li><a href="../rig/rigit.html">Rigging guide</a></li>
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<li><a href="../photo.htm">Photography guide</a></li>
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</ul></li>
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<li><a href="../../infodx.htm">Index to info/topics pages</a></li>
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<li><a href="../../indxal.htm">Full Index to area 1623</a>
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<ul>
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<li><a href="../../areas.htm">Area/subarea descriptions</a></li>
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</ul></li>
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<li><a href="../../index.htm">Back to Expedition Intro page</a></li>
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<li><a href="../../../index.htm">Back to CUCC Home page</a></li>
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</ul>
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</body>
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</html>
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