expo/expoweb
1
0
Fork 0
mirror of https://expo.survex.com/repositories/expoweb/.git/ synced 2025-12-08 06:45:00 +00:00
Code Issues Packages Projects Releases Wiki Activity

knitting in docmn for writing logbook entries, fixing old survey methods

Browse Source
This commit is contained in:
Philip Sargent
2018-08-09 11:31:45 +02:00
parent e4e88a73d7
commit a3ff1cacc2
9 changed files with 92 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

49
handbook/survey/ontop.htm
View File

@@ -1,7 +1,5 @@
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>CUCC Expo Surveying Handbook: Surface surveys</title>
<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
</head>
@@ -10,18 +8,9 @@
<h2 id="tophead">CUCC Expo Surveying Handbook</h2>
<h1>Surface surveys</h1>
<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>
<h3>Surface surveying is different</h3>
<p>
<a href="../../piclinks/ssvypl.htm"><img src="../../tinypix/ssvypl.jpg"
width="122" height="122" alt="" class="onleft" /></a>
@@ -33,8 +22,9 @@ 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.
<p>
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
poor compass/clino/distoX angle 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
@@ -42,13 +32,16 @@ survey legs short (6m gives a compass/clino error comparable with a 5cm
station position error). This makes the survey take much longer, and maybe
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>
<p>Using a distoX above ground does make it hard to see the laser spot in bright
sunlight of course, which limits the length of legs (except at dusk).
<p><b>Don't neglect sketching!</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
build to a map of the area, showing which bits have really been looked at.
<p>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
@@ -62,6 +55,32 @@ readily be found again, for example a drilled hole in a prominent boulder
easier to find end point - better to lose one or two legs than have to redo
the whole survey!</p>
<h3>Entrances and holes</h3>
<p>All features of speleological interest should have their position recorded exactly.
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.
This usually means using a handheld GPS device rather than a phone unless you have a particularly
good GPS app which provides an averaging function.
<p>If you are close to a big cliff, or almost inside an overhang, then an averaged-GPS will be good (~ 2m accuracy)
for latitude/longitude but appallingly misleading for altitude. In some parts of our area, such as the steep cliffs of
the Weisse Wand near Schnellzugh&ouml;hle (as seen in <a href="../../piclinks/ssvypl.htm">the photo at the top of this page</a>),
altitude is important for route-finding so GPS becomes surprisingly much less useful for re-finding locations. Before you use
GPS you really should read <a href="gps.htm">GPS for entrances</a>.
There is more about GPS altitudes in <a href="coord.htm">Olaf's article on GPS in Austria</a>.
<p>Without GPS we need an old-fashioned survey location using fixed points
with a minimum
of two bearings on fixed landmarks (see <a href="../findit.htm">taking bearings
</a> page for how to do this and for pictures of the various peaks we use).
<p>Anything
which gets a number (e.g. 2018-ad-01) should eventually be linked into an existing surface
survey. The number (on a metal tag) will 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. Always fix new stuff with a
GPS (use waypoint averaging) as even if this is not full survey-quality it does prevent things getting lost.
There is a separate manual page for <a href="gps.htm">using GPS for entrances</a>.</p>
<h3>Finding a starting point</h3>
<p>If your new cave is near a well-documented one, then a short connecting