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*fix and GPS
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@ -117,7 +117,9 @@ of any new question marks, with an estimate of quality and any difficulties
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which will be encountered (eg. if it is a climb, are bolts going to be
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needed ? If a dig, is it a few loose boulders or a crawl over mud?)</p>
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<h3>Archaic: hand-drawing the final survey</h3>
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<p>The actual published cave-survey is produced by software these days.
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These notes come from a different age but reading them will make your tunneling better
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and more polished:
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@ -146,7 +148,7 @@ For pitches, several plans at different levels may be easiest (rather like
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the cross sections at each survey station used in horizontal passage). Also
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projected elevations may be useful in addition to the extended section. But
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learning a good set of procedures for using survex is the way to go.</p>
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</em></div>
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<p>If you did all that properly, there should be very little left to do in
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the UK, unless you have volunteered to help with drawing up the final survey.
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@ -158,7 +160,7 @@ experience: it's now late April 2004, and the 204 survey is only just
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approaching completion. This shows how easy it is for these things to go wrong.
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The chief problems were a change of software and the fact that the Expo printer
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broke down last summer, so a number of surveys never got drawn up. -->
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</em></div>
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<hr />
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<p>Back to the previous page in this sequence <a href="newsurvex.html">Starting a new survex file</a>.
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@ -45,10 +45,53 @@ This page outlines step 7 of the survey production process. Each step is documen
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</p>
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<h3>Edit Entrance form</h3>
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<p>New in 2021 are fields for the latitude and logitude (WGS84 - the same as your GPS displays). These should be entered in degrees with decimals for fractions of a degree, e.g. 42.357 (not 42 degress 21 minutes 25 seconds, or 42 degrees 21.42 minutes).
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<p>These fields exist for newly-discovered cave entrances for which we currently have no location information except for a GPS reading by the original discoverer. These discoveries have a habit of getting completely lost: so enter it so that someone can find it again to properly survey it. In due course, proper surveys will be done and the cave will be linked in to the GPX and survex survey system. If this has been done, then that is authoritative and you do not need to enter location informaiton on this form.
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<p>In previous decades the location of an entrance was the <em>output</em> of a whole lot of surveying and position fixing (e.g. see <a href="lasers.htm">laser points</a>). Today, an initial location of an entrance is available by GPS at the <em>beginning</em> of the process. So we have these fields to record the data. [We don't yet have the code to automatically add these to the <var>essentials.gpx</var> download to be used for prospecting though.]
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<ul>
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<li>There are labels on the fields which explain what they mean - read the labels.
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<li>There is popup information on some of the fields if you hover your mouse over them, try it.
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<li>If you still don't understand the purpose or meaning of a field, read <a href="ententryfields.html">the documentation</a>.
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</ul>
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<h4>WGS84 fields on the form</h4>
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<p>New in 2021 are fields for the latitude and logitude (WGS84 - the same as your GPS displays). <b>Unless</b> someone has already created the *fix point for the cave, these should be entered in the form. IF the *fix <em>has</em> been done, then <em>leave the WGS84 fields blank</em>.
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<p>We always write degrees with decimals for fractions of a degree, e.g. 42.357 (not 42 degrees 21 minutes 25 seconds, or 42 degrees 21.42 minutes).
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<p>These WGS84 fields exist for newly-discovered cave entrances for which we currently have no location information except for a GPS reading by the original discoverer. These discoveries have a habit of getting completely lost: so enter it so that someone can find it again to properly survey it. In due course the cave will be linked in to the survex survey system using *fix statements. If this *fix work has been done, then that is authoritative and <em> you do not need</em> to enter location information on this form.
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<h3 id="fix">More details about *fix statements</h3>
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<p>When a nerd creates a *fix statement, in the right place, the nerd will manually delete the WGS84 values on the Entrance.
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<p>
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The survex location uses a *fix statement and it looks like this:
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<code>
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*cs LONG-LAT<br>
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*fix p2023-js-02 reference 13.80841 47.69055 1745<br>
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*entrance p2023-js-02
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</code>
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<p>If you are doing this for the first time, it might be a good idea to put it in the same survex file temporarily. A nerd will move it to the right place later.
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<div style="margin-left: 3em; margin-right: 4em"><em>The 'right place' is in the <var>fixedpts</var> part of the <var>:loser:</var> repository, but is very different depending on whether the cave is in the 1623 or the 1626 area - for historic reasons
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</em>
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<p>For the 1623 area it is easy. Each year has a different file. For 2019 there is a file <var>gps/gps19.svx</var> which contians all the *fix statements for new locations that year.
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<p>For the 1626 area it has got horribly complicated and you should talk to Wookey and Becka. Most likely it will have to go into <var>fixedpts/1626-no-schoenberg-hs-not-tied-to-caves.svx</var></div>
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<p>And in your main survex file you will need to make the connection between the survey points in the cave and the external location. This would be something like this (not real data), where survey station "1" is the tag at the entrance of the cave, and outside the begin/end section it is called "2023-js-02.1"
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<code>
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*equate p2023-js-02 2023-js-02.1<br />
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<br />
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*begin 2023-js-01<br />
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*export 1<br />
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...<br />
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*data normal from to length bearing gradient ignoreall<br />
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1 2 4.46 099.3 -54<br />
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...<br />
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*end 2023-js-01<br />
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</code>
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<p>There is a lot more to say about how to record the best GPS data, and how to link GPS with survey points, e.g. see <a href="gps.htm">Getting a GPS fix</a>
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<p>In practice, for us on the plateau, we get repeat measurements of the same spot by different teams in different years to be accurate to only about 3m. This is fine for finding entrances, and for checking whether two different teams have found the same cave, but it is not adequate for loop-closure. That requires particular care with averaging the reading over 2 minutes, and use of a location with good view of the sky, away from vertical rock, and surface survey using instruments to get from the GPS point to the actual cave entrances. To get a decent <em>altitude</em> measurement requires averaging over 10 minutes, and it is still not good.
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<p>In previous decades the location of an entrance was the <em>output</em> of a whole lot of surveying and position fixing (e.g. see <a href="lasers.htm">laser points</a>). Today, an initial location of an entrance is available by GPS at the <em>beginning</em> of the process. So we have these fields to record the data. [We don't yet have the code to automatically add the *fix statements into the <var>fixedpts</var> data, or to the <var>essentials.gpx</var> download to be used for prospecting though.]
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<h2>List of New Entrance/Entrance_data fields</h2>
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<p>The full list of fields is documented: <a href="ententryfields.html">the full list of data-entry fields</a> when creating an entrance.
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@ -18,11 +18,12 @@
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</p>
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<h3>Only one field is essential for Entrances</h3>
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<p>There is only one essential field which must be there before the Submit button will work:
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<h3>Only two field are essential for Entrances</h3>
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<p>There are only two essential fields which must be there before the Submit button will work:
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<ul>
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<li><b>marking</b> e.g. Tag or Paint
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<li><b>Marking</b> e.g. Tag or Paint
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<li><b>Findability</b> e.g. Lost or Coordinates
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</ul>
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<p>See below for explanations.
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@ -57,7 +58,7 @@
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<dl>
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<dt>photo</dt>
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<dd>Put an <img> tag in here, as for the cave description. See how images are managed for caves, and do the same thing for this entrance. <em>HTML freeform field.</em></dd>
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<dd>Put an <img> tag in here, as for the cave description. See how images are managed for caves, and do the same thing for this entrance. <em>HTML freeform field.</em></dd>
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</dl>
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<dl>
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<dt>marking</dt>
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@ -65,7 +66,7 @@
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</dl>
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<dl>
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<dt>marking_comment</dt>
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<dd>A text field: where is the tag? <em>HTML freeform field.</em></dd>
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<dd>A text field: what colour paint? Where was the aluminium tag place?? <em>HTML freeform field.</em></dd>
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</dl>
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<dl>
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<dt>Findability</dt>
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@ -79,39 +80,28 @@
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<dt>Altitude (metres)</dt>
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<dd>In old caves this will have been calculated in UTM coordinates. Enter your GPS value here (WGS84). Yes, altitudes are slightly different. This will be overwritten in due course by an altitude derived from the location and the lidar dataset.</dd>
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</dl>
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<dl>
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<dt>Northing</dt>
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<dd>calculated position in UTM</dd>
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</dl>
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<dl>
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<dt>Easting</dt>
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<dd>calculated position in UTM</dd>
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</dl>
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<dl>
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<dt>latitude</dt>
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<dd>Decimal degrees of longitude in WGS84 datum. To be entered when entrance is first found so that someone can find it again. Will be overwritten in due course by proper survey data which will be enforced to be consistent with the UTM position.</dd>
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</dl>
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<dl>
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<dt>longitude</dt>
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<dd>Decimal degrees of longitude in WGS84 datum. To be entered when entrance is first found so that someone can find it again. Will be overwritten in due course by proper survey data which will be enforced to be consistent with the UTM position.</dd>
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<dd>Decimal degrees of longitude in WGS84 datum. To be entered when entrance is first found so that someone can find it again. This will be deleted here when a proper tag station or other station is created</dd>
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</dl>
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<dl>
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<dt>tag_station</dt>
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<dd>a survey station id. It has to be in a format similar to this: "1623.p204e" (for the 'e' entrance to cave 1623-204)</dd>
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<dd>a survey station id. It has to be in a format similar to this: "1623.p204e" (for the 'e' entrance to cave 1623-204). This is where the aluminium ID tag is bolted at the entrance.</dd>
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</dl>
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<dl>
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<dl>
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<dt>exact_station</dt>
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<dd>a survey station id. It has to be in a format similar to this: "1623.p204e" (for the 'e' entrance to cave 1623-204)[to be documented further - use Edit This Page!]</dd>
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</dl>
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<dl>
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<dl>
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<dt>other_station</dt>
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<dd>a survey station id.It has to be in a format similar to this: "1623.p204e" (for the 'e' entrance to cave 1623-204) [to be documented further - use Edit This Page!]</dd>
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<dd>a survey station id. It has to be in a format similar to this: "1623.p204e" (for the 'e' entrance to cave 1623-204) [to be documented further - use Edit This Page!]</dd>
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</dl>
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<dl>
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<dt>other_description</dt>
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<dd>[undocumented?] Filename?: the name of top-level description file for this cave, when a separate file is used. Used instead of above entrance_description field for large caves with complex descriptions. Blank if the description is in the 'underground_description' field. </dd>
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<dd>Continuation of the description is in the 'underground_description' field if you have more to say. </dd>
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</dl>
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<dl>
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<dt>bearings</dt>
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@ -119,10 +109,10 @@
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</dl>
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<dl>
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<dt>url</dt>
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<dd>Usually blank</dd>.
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<dd>Leave blank. The correct value is computed.</dd>.
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</dl>
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<h4>ALternative data entry using a file</h4>
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<h4>Alternative data entry using a file</h4>
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<p>
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There are template files for you to fill-in when creating new caves and entrance in the online system. You will need to be on a machine which has
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<a href="../computing/keyexchange.html">keys installed</a> and you will need to know how to use git.
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BIN
handbook/survey/fix-2023-js-02-new.jpg
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handbook/survey/fix-2023-js-02-new.jpg
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handbook/survey/fix-2023-js-02-notes.jpg
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handbook/survey/fix-2023-js-02-notes.jpg
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After Width: | Height: | Size: 16 KiB |
@ -4,7 +4,6 @@
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<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
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</head>
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<body>
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<h2 id="tophead">CUCC Expo Surveying Handbook</h2>
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<h1>Locating entrances by GPS</h1>
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@ -27,6 +26,7 @@ landmark with a wide, clear view of the sky, and within one (or maybe two) surve
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of the entrance. If you have found a group of caves close together, it
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might be better to GPS a central point rather than get quick (but less
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accurate) fixes on each entrance.</p>
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<p>Yes, you will have to manually do a surface survey leg using your survey instruments between the GPS point and the cave entrance tag station, and record that in your cave survex file.
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<p>We now (2018) have differential GPS which is much more accurate than
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in the past (e.g. Wookey's 1996 article) but altitudes are often very inaccurate
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@ -61,8 +61,5 @@ on coordinate systems</a> has been moved to a different page. If you are really
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<a href="coord.htm">Olaf's article</a>too.
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<hr />
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</body>
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<hr /></body>
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</html>
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@ -58,6 +58,7 @@ actually do these things.
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<li>Transcribe your sketches onto centre-line paper
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<li>Scan your centre-lined sketches
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<li>Use therion or tunnel to digitise your centre-line sketches
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<li>Connect your survey to the surveys of other caves by fixing the entrance location.
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</ul>
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<p>and either later or at the same time, you will be doing these other tasks
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<ul>
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@ -97,7 +98,8 @@ New cave process
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│ ├── How to create a survex file - PDF - Brendan's guide
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│ ├── From muddy book to survex plot
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│ ├── Cave description
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│ └── Adding QMs (Question Marks)
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│ ├── Adding QMs (Question Marks)
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│ └── Fixing the entrance location
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├── 4 Drawing up your survey
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│ ├── How to use Tunnel - PDF - Brendan's guide
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│ ├── Guide to using Tunnel - PDF - David Loeffler's guide
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@ -114,9 +116,10 @@ New cave process
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│ ├── Edit this cave
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│ └── the full list of data-entry fields
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├── 7 Creating a new entrance in the online system
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│ └── Entrance entry page fields
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│ ├──cave_data template
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│ └──entrance_data template
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│ ├── Entrance entry page fields
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│ │ ├──cave_data template
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│ │ └──entrance_data template
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│ └── Entrance locations in more detail
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├── 8 Next steps
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│
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Back in the UK</textarea></code>
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@ -45,6 +45,39 @@ This page outlines step 3 of the survey production process. Each step is documen
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</figcaption>
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</figure>
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</div>
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<h3>Fixing the location of the entrance</h3>
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<div class="onright">
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<figure>
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<a href="/walletedit/2023:17">
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<img src="fix-2023-js-02-notes.jpg" ></a>
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<figcaption style="font-variant-caps: small-caps;">
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<em>At cave sketch notes [July of course, not June]</em>
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</figcaption>
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</figure>
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</div>
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<ul>
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<li>We won't be able to see where your cave may link in to others <b>if we don't know where it is</b>.
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<li>We won't be absolutely sure that your cave is actually a new cave <b>unless we can check it off</b> the locations in our records.
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<li>If your cave does link to another, we need to know where the entrances are <b>with respect to each other</b> so that we can compute the loop-closure errors and improve the quality of the surveys.
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</ul>
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<p>So this is important.
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<div class="onright">
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<figure>
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<a href="/walletedit/2023:17">
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<img src="fix-2023-js-02-new.jpg" ></a>
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<figcaption style="font-variant-caps: small-caps;">
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<em>New Cave Sheet location and altitude</em>
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</figcaption>
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</figure>
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</div>
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<p>Now, in 2023, we have mobile phones which can get a GPS location directly from the satellites without requiring a 'mobile signal'. We find that relying on one of the party recording a continuous 'track', and then extracting the locations later, is very prone to human error. The worst and most common error is that everyone forgets to do this.
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<p>The (strongly) recommended procedure is to take a specific GPS measurement at a well-defined point and to write down the location on your prospecting survey notes. Then for a new discovery it will be copied onto the New Cave data sheet.
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<p>Note that we record the location in degrees and decimals of degrees: <code>47.69055 13.80841</code> and the altitude is in metres.
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<p>The altitude is not nearly as vital as the lat/long numbers. GPS altitudes are still pretty bad, and even the new Galileo system won't promise anything better than ± 0.4m in 2030. (If you take the altitude from a track while moving the altitude can easily be 15m wrong.)
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<p>See <a href="#location">the bottom of this page</a> for how the location information is typed in.
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<h4 >Two ways to type in survex data</h3>
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<ul>
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@ -208,6 +241,35 @@ telling them to use the online form.]
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entering the QM data into a survex file.
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</p>
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<h3><a id="location">Entering the Entrance location data</a></h3>
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<p>The location of the cave is, eventually, stored in a survex file, just <em>not the same survex file</em>.
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<p><b>If you are doing this for the first time</b>, don't bother with this *fix stuff. Just type the latitude & logitude numbers into the <a href="ententry.html">New Entrance form</a> and someone else will do the *fix stuff.
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<p>
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The survex location uses a *fix statement and it looks like this:
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<code>
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*cs LONG-LAT<br>
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*fix p2023-js-02 reference 13.80841 47.69055 1745<br>
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*entrance p2023-js-02
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</code>
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<p>If you are doing this for the first time, <em>do</em> put it in the same survex file. A nerd will move it to the right place later.
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<div style="margin-left: 3em; margin-right: 4em"><em>The 'right place' is in the <var>fixedpts</var> part of the <var>:loser:</var> repository, but is very different depending on whether the cave is in the 1623 or the 1626 area - for historic reasons
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</em> </div>
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<p>And in your main survex file you will need to make the connection between the survey points in the cave and the external location. This would be something like this (not real data), where survey station "1" is the tag at the entrance of the cave, and outside the begin/end section it is called "2023-js-02.1"
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<code>
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*equate p2023-js-02 2023-js-02.1<br />
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<br />
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*begin 2023-js-01<br />
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*export 1<br />
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...<br />
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*data normal from to length bearing gradient ignoreall<br />
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1 2 4.46 099.3 -54<br />
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...<br />
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*end 2023-js-01<br />
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</code>
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<p>There is a lot more to say about how to record the best GPS data, and how to link GPS with survey points
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<h3><a id="tickingoff">Entering the cave description in the survex file</a></h3>
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<p>The last part of the survex file is a description of the passage surveyed. Remember
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that this is intended to be read by people
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Block a user