Surveying Caves - Part I


It gives me great pleasure to present this first in a series of articles for publication in the Croydon Caving Club's illustrious organ. When I was finally 'tempted' by those nearest and dearest to me to put pen to paper after what was thought by many to be my premature retirement from underground activities; I gave much thought to what great contribution could I make? Originally it had been my intention to write an article on 'Alternative Calcite Mining Techniques' or 'National Parks Law Enforcement' but instead I found myself drawn to surveys and attracted to the tools instrumental in the production of them. I therefore commend to you this body of knowledge that I have accumulated and feel that many would benefit by absorbing it (not).

Moonrat - November 1998

1. Purposes of a Cave Survey

The majority of cave surveys are not meant for fulfilling a particular specific use but are instead useful for a number of purposes. Most cave surveys it will be noted are just basically too big to be taken into the very caves they are of; this is not however a deliberate over-sight. A miniature version would not be so easy to read underground neither would it be such an ideal source of cheap wall-paper. This type of decoration is most often seen gracing 'digs' owned by students pretending they're hard/experienced cavers and thirty plus knackered old cavers pretending they're still students.

The aim of the surveyor should always be to make the most accurate survey of the cave as is possible in the time available before their speleological career ends. This is most commonly due from either the debilitating effects of old age, death and/or marriage; all of which have identical and eventually terminal results on the surveyors ability to venture underground to collect data. Several examples of the different phases in the life cycle of a cave surveyor have been observed in Ogof Draenen where the survey team have so far spent 4+ years and 8000+ man hours of effort producing a particularly large piece of speleological wallpaper. (This amount of effort is at once commendable but also incomprehensible but it does go a long way to explain why various antagonists have been singly unable to prevent the surveyors producing an admirable survey of the cave.) Births, marriages, death like feeblement have all been observed and had a consequential affect on the individual's willingness to perform abnormal acts underground with their fellow cavers.

Some other popular uses for a cave survey include...

(a) a source of diversion in attempting to delay exit from the cottage before the next mug of tea arrives.
(b) a table-cloth for bickering over if the cave has been exited very, very late and the local public house has closed.
(c) Bullshit
(d) a source of information that may interpreted in a thousand ways giving armchair cavers a perfect base to argue with young tigers as to why their dig is a speleological dodo; this often occurs just before the dig breaks into cave passages of satanic proportions. If a survey has been drawn well then all preceding geological theories may however be dispensed with easily and a new set created.
(e) more bullshit

2. Precision of a Cave Survey

There are two basic approaches to reducing the effect errors have on the survey. The first technique attempts to minimise anything and everything that might cause inaccuracy in the readings. This method although popular amongst the older caving establishment has recently been put into doubt by modern new age thinking promoted by the impatience of youth; mainly it would seem in order to ensure that they trample down more virgin passage before anybody else. This new approach is good for producing surveys that are of use as an aid to the explorer's further ambitions, ego and bragging in the pub.

It has been shown by highly complicated, sophisticated and basically dubious theories that when enough errors are combined they tend to cancel themselves out. The secret of a highly accurate survey therefore can be to introduce as many errors into everything that everybody does so that numeric karma is achieved. Although a greater sense of tranquillity and peace is experienced when surveying this way, it is often mistakenly interpreted as 'not trying'. Glaring inaccuracies may however always be dismissed by explaining that those taken during the next trip will balance all dubious readings out. (See Joints). When using this method however, it must be noted that every element involved in producing the survey must contain an equal quantity of inaccuracy; the presence of a single surveyor who is perfect and faultless will cause trouble.

It is useful for the user of a survey to have an idea of the claimed accuracy so that he/she/it can decide on a). the likelihood of getting lost; b) the amount of derision that might be encountered if caught publicly studying it too seriously c) the street-cred associated with it if used as wallpaper. The true accuracy of a survey may however never be known as most surveyors will usually bend the rules during it's production. It is not uncommon to falsify passage details to hide connections, alternative (easier) entrances, good dig sites and pretty stal that novices and diggers cannot be trusted near. Most of these 'cartographic sins' are justifiable if one remembers to drop the word conservation into the dialogue often.

Survey Grades

The following grades refer to the claimed accuracy of the centre line of the survey. Cave surveys also consist of the detail added to this centre line, and the artistic flair/license or imagination possible with a blunt and muddy pencil.

Grade 1 - A vague memory of large passages being run down to lord knows where. Good in the Pub this one as it conveys the most passage and glory to the audience with the minimum amount of hassle underground. A sketch on the back of a beer mat is especially useful as an aid for navigation if the cave passage amounts to 20km+. Also known as the 'X X X X' grade survey.

Grade 2 - The above with some modicum of reality. It is usually possible to convert a Grade-1 survey to a Grade-2 by halving all boasted passage lengths and dividing pitch lengths by three. Unlike a Grade-1 survey it is not affected by the consumption of intoxicating liquor.

Grade 3 - A rough magnetic survey or a survey when YOU are feeling rough. This has the advantage of being the lowest grade which tells you where the cave is actually going and how long it is. The disadvantage is that instruments have to be used and you have to work as a team. Not using instruments such as a clinometer means that the cave will have no measurable depth which can however often make it easier to get out.

Grade 4 - The most common grade of survey, this is often written as 'Grade-5' on surveys by cavers who ought to know better. Most caverns if asked, would like to have a Grade-5 done of them when they are discovered but then potholers get involved and pubs only stay open until 11:00pm.

Grade 5 - A good survey in which some personal relationships may come under strain as well as your eyes trying to read that 0.25 degree thru' the instruments.

Grade 6 - Obsessive behaviour for subterranean anoraks that can result in a work of art and admiring questions like 'Why??'. BlueTac is not good enough for this type of survey, a frame may be required.

Grade X - Useful only for long underground passages like the Channel Tunnel for instance.

Classification of survey detail...

Class A - Use your arms to show how big it is or simply compare it with the best cave that everybody else knows.

Class B - A sketch showing some passage details. Unlike Class-A it actually proves that caves have two walls not just one.

Class C - Shows caves can have small passages as well as big ones. These make the cave longer as well as easier to get lost in.

Class D - Measurement and drawing of such fine detail that will be lost on both the survey and those impatient members of the team waiting to shout out the next survey measurements.

In summary one will realise that there are really only two basic types of survey; these can be termed "bad" and "probably Ok". This broad classification into only two types agrees with theoretical studies that have been made into what happens when you try to use them underground or amongst those with less than clean hands. The survey user need only remember that a low grade survey conveys approximately the same amount of information about the cavers involved than an accurate grade 5 does about the actual cave involved. If there is a desire to know more closely the probable accuracy of a cave survey then reference can be made to the diagram that follows. Alternatively get the surveyors very drunk and find out what really went on.

3 General Principles of Surveying

In this section we will cover the actual recording of cave survey data. While it is possible for a lone surveyor to make an accurate survey, it is recommended that a survey team consists of at least two people and more usually three or four. This is for a number of good reasons ...

(a) solo surveying survey things that are longer than ones arms causes obvious difficulty unless the far end of tape can be jammed into cracks or boulders. A sometimes useful technique however when you suddenly 'find' yourself separated from the rest of the party on the wrong side of a tight squeeze with the book, compass, clino, tape....

(b) no matter how good your survey is of the gorgeous cave you have just discovered, absolutely no one will believe you until they have been there along with all their mates (usually) from other Clubs.

(c) there is less chance of being volunteered for unpleasant tasks like being neck-deep in water holding the tape and determining the depth and how horrible it is.

(d) lots of underground food that is better than yours.

(e) lots more banter and crude jokes that takes ones mind off the tedious and unpleasant tasks underground, like surveying for example.

The Team

A party of three can divide the work as follows. One person to take the instrument readings (good eye-sight and a steady hand is essential, usually the one that was sober enough to drive back from the pub the night before).

A second to record the numbers and makes sketches, usually the neatest writer and most artistic in talent (and temperament). Try to avoid anybody with a non-contemporary style like avant-garde or surrealist as this can affect the final result - it is rumoured that the Ogof Ffynnon Ddu survey was touched by cubism (as were allegedly some of the Westminster Speleo Group members whilst on expedition)

The third holds the far end of the tape and can act as a general factotum (!), surveyors dog, beast of burden, step-ladder and potential accomplice in rebellion when the lead surveyor needs to be reminded that the outside world includes things like pubs and beds.

Before starting on a survey trip, it is preferable that the lead surveyor should be certain that each of his 'volunteers' knows as little as possible about surveying. Only by doing this will the trip get to where it is planned to go and carry out the exercise of surveying before a complete mutiny takes place. One disadvantage of this is that very soon within a finite population of cavers all of them will develop excuses for being elsewhere and a sudden interest in unlikely subjects such as the opposite sex, child rearing and cottage maintenance. The other disadvantage is that it takes ten times as long to do anything and the end result gives a mistaken impression that nobody knew what they were doing.

Alternatively the lead surveyor may choose the risky but ultimately more productive strategy of gathering together a group that have a vague idea of what they are expected to do and how to do it. The lead surveyor should always ascertain the competency of his party... - Is the person who will be reading the instruments familiar with them and know what to precision each reading is expected? +/- 0.5o, +/- 1o, +/- 5o and North'ish, East'ish, South'ish, and the other one.

  • Do they know that giving alternate readings in Gradients and Degrees and/or metric/imperial is punishable by hanging (or worse) in some far off countries where caves are only just now being explored and surveyed properly, like Wales for instance.
  • Are they aware that measuring bearings with a clino is futile but that recording an inclination read from a compass is possible if the person with the book isn't concentrating.
  • Does everyone have 'left' and 'right' written on their caving gloves?
  • Do they understand complicated surveying jargon such as 'on the big rock', or 'behind you'.
  • Does the tapeman understand that space may be curved but this doesn't justify using it's properties to get 30 metre long legs.

Attention to detail like the above will save frustration and also probably your voice from explaining what reading you want for the n'th time.

The method of recording information obtained in the cave is a matter of opinion. Experienced surveyors usually devise a shorthand system that is quick but quite incomprehensible to others including the poor sod who has to transfer the data onto the master. It is often noticed that by the end of a long arduous trip the lead surveyor becomes so adept at this that at 3:00am in the morning even he's not sure what he has just written. Various types of durable notebooks are usually the preferred medium for writing on. (An example of a record sheet is shown below). Water proofed paper is very good in wet and muddy conditions but has the disadvantages of being expensive and ineffectual when caving abroad if last night's donkey stew suddenly disagrees with you. Any ruined notes that are to be disposed of should always be marked by writing an appropriate comment across them like 'void' or 'Andrex'.

This concludes part I of 'Surveying Caves, subjects covered in later issues will include...

Plotting - how to find the ring leaders
Cave Surveying for Sad Computer Boffins
Underwater Surveying - Your Equipment, Magnetism and Futility

 Paul Stacey (With apologies to Bryan Ellis....)

Paul Stacey