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updated gps - online edit of handbook/survey/ontop.htm - on dev machine 'SnowWhite'

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Philip Sargent
2025-05-22 09:15:12 +01:00
parent 674c5a1650
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1 changed files with 6 additions and 17 deletions
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handbook/survey/ontop.htm
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@@ -4,7 +4,6 @@
<link rel="stylesheet" type="text/css" href="/css/main2.css" />
</head>
<body>
<h2 id="tophead">CUCC Expo Surveying Handbook</h2>
<h1>Surface surveys</h1>
@@ -57,11 +56,11 @@ 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.
These days (2025) a medium-average GPS location (3 minutes: i.e. 1,000+ GPS "events" inside your device) is fine (see <a href="gps.htm">GPS for entrances</a>) in most parts of our caving area.
(This is not "accurate": it will be perhaps 5m off if you measure the same spot the next day when the ionosphere is in a different mood, and any altitude you get will be absolutely useless.)
This usually means using a handheld GPS device rather than a phone unless you have a specifically accurate GPS app (e.g. OSMand) which provides both an averaging function and does not assume that you are a cyclist or fell-runner (most Garmin devices in 2025).
<p>If you are close to a big cliff, or almost inside an overhang, then an averaged-GPS will be good (~ 2m accuracy)
<p>If you are close to a big cliff, or almost inside an overhang, then an averaged-GPS will apparently 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
@@ -71,7 +70,7 @@ There is more about GPS altitudes in <a href="coord.htm">Olaf's article on GPS i
<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).
</a> page for how to do this and for pictures of the various peaks we used to use). This is now a forgotten skill.
<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
@@ -125,15 +124,5 @@ best are surface surveys taking a short route from these points.</p>
<li><a href="../rescue.htm">Rescue guide</a></li>
<li><a href="../rig/rigit.html">Rigging guide</a></li>
<li><a href="../photo.htm">Photography guide</a></li>
</ul></li>
<li><a href="../../infodx.htm">Index to info/topics pages</a></li>
<li><a href="../../indxal.htm">Full Index to area 1623</a>
<ul>
<li><a href="../../areas.htm">Area/subarea descriptions</a></li>
</ul></li>
<li><a href="../../index.htm">Back to Expedition Intro page</a></li>
<li><a href="../../../index.htm">Back to CUCC Home page</a></li>
</ul>
</body>
</ul></body>
</html>