Expedition Surveying Guide

Wookey, Andy Atkinson and Anthony Day
1995 version

This weighty document is the numpty's guide to surveying. The authors intend it to be read. It is not meant to be used for propping up wobbly table legs or filling holes in rusty sills. There are two sections on surveying, writing up of surveys. It is largely derived from a doc prepared specifically for Cambridge University Caving Club.

1. How to Survey

Ask n surevyors how to do it and you will get n aswers, so this is necessarily biased by my knowledge & experience.

1.1. Intro

The idea of the survey is to record the cave as best you can. This being expedition caving, time is limited, but don't forget that no-one else may ever come here again, so the idea is to efficiently record as much info as possible. You are collecting data to fulfil a number of needs: the actual position of the passage for finding where it goes & possible connections; geological info for working out how it got there; the shape of it for drawing pretty surveys, to prove that you actually achieved something.

Equipment

*Pencils: propelling generally better. Take several & a knife. Have spare leads at base. Pick ones the rubbers are hard to knock off (eg Bic).

*Paper: How wet is it? Rag paper (chartwell is good) if only damp, or ocaisionally drippy, plasticised paper can be good if wet, but use soft pencils or writing will rub off. Take lots.

Aluminium books + bulldog clip to hold notes,

Notebooks are handy but unless you rip out the pages you will take old surveys back into the cave which can be risky.

Clipboards for comfy large warm caves

*Insts: Suunto good but expensive. Silva type 80 also good. Silva Twin is both insts in one block option. Don’t buy ones with backsights on unless you are doing them, as it only gives people the chance to use the wrong scale.

Lighting- built-in LEDs are good -(see Compass Points). Otherwise use external (care needed!)

Seal instruments - store in dessicator (‘bide/silica gel) for cold areas. Also use silcon sealant/araldite. For humid areas, get ones with ports for flushing.

Suunto’s can be bought cheapest in UK from BCRA Cave Surveying Group.

*Tape:fiberglass is best (metal ones kink and snag). 30m is good. Small ones tend to fill with mud. Open reels break. All tapes break or numbers rub off.

Processing:

Can use ruler & potractor at a pinch, but Calculator & graph paper much better.

Computer has major advantages (visualization, speed) & disadvantages (size, cost)

Somthing like Psion & baby inkjet may be good compromise (except I don’t know of any software yet).

1.2. Survey Method

READ A BOOK - ‘Intro to cave surveying’, or ‘cave surveying’ - both by Bryan Ellis.

Very hard to do well until you have tried to use somone else’s info to draw up.

The idea is to leap frog along the cave measuring the direction, derivation and length of the legs, while recording the dimensions and sketch of the passage. Leapfrogging means that if the first leg is measured from station 1 to 2, the second leg should also survey to station 2 (ie from station 3 to 2), then proceed 3 - 4, 5 - 4, 5 - 6, 7 - 6 etc. Easy. Around this is drawn the cave in 3d (ie plan, elevation and cross sections). However the amount of information collectable is infinite and time is usually short, so set out here is what is considered the essential information and a few ways to collect it.

•Survey stations should be well-defined (eg fixed points like bolts, carbide marks, obvious features etc) such that you can draw straight lines between them without intersecting the walls (obvious, but you'd be surprised how many bent survey legs are found.)

Teams of two, three or four are used. If there are two of you it is generally accepted that one reads the instruments while the other writes it down and sketches. With three two people can do as above while the third scouts for stations or one can do the instruments, one records the figures and the third sketches (requires co-ordination between the two note-takers). If there is a fourth person they can do the other end of the tape, and scout for leads.

As for the recording of information, some people prefer to list a few stations on one piece of paper along with the sketch of the plan and elevation, while others use one page for a table of information and use another sheet for the sketch.

Survey stations at intersections and the end of surveys should be permanently marked (an 'S' is usual) and recorded in the notes. This should also be undertaken on long passage seemingly junctionless as it is not unknown for passages to appear from nowhere.

A grade 5c survey is one of a pretty respectable standard. For very small caves or when exceptionally short of time lower grades (3 & 4) can be sensible. The information below is the minimum that can be collected to for grade 5c.

Compass and clino read to the closest degree (halves are OK if you like).

Tape to the closest centimetre.

A cross-section with dimensions every time the passage changes significantly.

The left, right, up, down (LRUD) from the survey station to the general passage wall, not the closest little piece of rock.

1.3. What to Write Down

1. TITLE - Date - Which cave - From where to where (connection points) - Who did what - Which instruments used - Calibration

2. DATA - example format illustrated below

From To F/B Tape Compass Clino Station Description LRUD
1 2 F 5/35 042 +171 Top corner of flake 0 1/15 2/50 0/45
3 2 B 7/50 227 +252 CM on roof 0/75 0/40 0 3/20
3 4 F 6/30 002 -053 CM on wall 1/25 0 ~5/00 0/45
4 5 F 10/13 - DOWN 4Pitch head bolt - - - -
5CM by rebelay - - - -

Notes:

3. DRAWINGS

Put on all survey stations, fixed points (eg bolts, including rigging details) section positions & directions, survey station LRUD plane, floor details, height changes (eg pitches & climbs) , water, draughts, leads etc

A work of art worthy of the Tate Gallery is not required, but it must look like the cave otherwise you will have a hard time drawing up the neat version in the survey book.

Try to draw a single continuous plan rather than one in six different bits as this is also hard to interpret when drawing up.

In vertical sections, elevations take the place of plans and should be drawn in the same way. Extended elevations are generally the most useful.

_Find out what the BCRA symbols are and use them

Draw 3d boulders for ones that exist.

4. CROSS-SECTIONS - should be drawn wherever the passage size/shape changes. Cross sections without a scale, orientation or position are useless - this info should be noted on the plan. Cross-sections need not coincide with survey stations, but where they do not the distance to the nearest survey station should be noted.

1.4. Calibration

Calibration is very useful for detecting errors in instruments, people’s eyesight and the local magnetic conditions. It can make a significant difference to accuracy. On expos, unless you have one or two very big caves it can be difficult to set something suitable up. A couple of cairns as the camp might be a good idea. Compass is best done between distant known objects (eg mountains) unless it is usually misty. Clino can be done between any two point, in both directions. Several readings for each calibration is best.

1.5. Points to Remember

Compass must be flatish to get a meaningful reading. Also take care with lights, batteries & helmets - check your gear on the surface, or your work could be seriously impaired. If your light affects the compass, then hold it away from the instrument when lighting it. Practice using the compass above ground to avoid classic errors like reading 56 as 64 (ie counting the wrong way from the 60 marker)

Degrees is the left hand scale on clinos. (Percent is better than nothing if you can't read the other scale, but reading the wrong one without realising gives useless results.)

_Read all numbers back in different format eg 50 - Five - oh

Pick survey points so you can get your head in, and so you can see both ways as easily as possible. Note that Bolts are good things to use as stations (because we can find them again), but don't put the compass within 20cm as it will give joke readings. Sight from the other end of the leg, or put the compass behind it and look past the bolt.

Have a separate front sheet without anything important on it to protect your actual survey notes.

Take at least one spare pencil!

Keep instruments in a dessicator (eg sealed container with a bit of carbide in it) to reduce risk of fogging

Leapfrogging is a good idea in general (it helps to eliminate station position & clino errors) but you don't have to be religious about it.

Draw extended sections in two directions for vertical cave, with plans where required. Mark directions on plans and sections otherwise they are impossible to orient later. A plan with only one station & no direction indicator cannot be oriented. It is easiest if the drawer takes a spare compass for this in vertical work.

Think ahead when surveying pitches, especially long ones. Take two tape measures for stuff over 30m.

_Plumb piches if at all possible. Steep legs are very hard. Short Horizontal legs into space are betterthan 40m shots at 79 degrees.

Find put where you are going to join your survey to before you go, otherwise your surveys will be left hanging in space.

1.6. Common Mistakes

No Calibration or record of who did what.

Forgetting part of the survey gear (especially second pencil.)

Bending survey legs (can be done without error if _both_ ends moved correspondingly)

Not marking permanent survey stations.

No dimensions on cross sections.

No cross sections.

Not written up in book back at camp.

Forgetting to mark stations on sketch.

No elevation recorded making it extremely hard to draw later.

No names when written up on sketch leading to other people naming it badly.

Recording too much causing low morale and little done. Boulders can be drawn over a beer in the potato hut and just a general note made underground.

Recording too little so it is essentially two parallel lines.

Survey what you find, don't leave it for someone else.

Survey from last point, don't run off finding loads of cave and survey back. This leads to very long nights.

Take care when holding your survey notes when using a carbide - they catch fire very easily.

2. Writing up Surveys

2.1. Intro

Exactly what you do at base camp depends greatly on circumstances. Here I assume a central survey book and computer/printer.

On returning to base camp, all the data needs to be written up neatly in the survey book and typed into the computer so a centre line can be printed to make the sketching easier. The data, calibration and sketch, marked with names and numbered question-mark or continuations should be written into the survey book while everyone's memory is still fresh. The question mark completed should be marked on the list with what supersedes it and the new leads numbered.

File the original notes! The original notes should be put into an envelope marked with the name of the bit of cave, date of survey (including year), and the names of the surveyors and filed with all the rest.

3. Software

There is a wide range of available survey software, and different software is better for different needs, abilities & computers. I recommend Survex for speed, power, language & system independence (and it’s free), but if you like software with menus everywhere then there are several competent pieces for Windows although none are free. There is also toporobot for the Macintosh, which is free & very good.


See also the Cave Surveying pages.


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