Well, you could say that the good times are back in GCG. A recent influx of new cavers and recent discoveries of caves needing exploration and mapping have made the conditions right for starting survey projects. For those of us who are project cavers, this is the true essence of caving.
So - if you like back-breaking work consisting of long hours crawling (slowly) through muck and mud, and shouting numbers to a bookkeeper who increasingly becomes the person you most hate in the whole universe - well- then you'll agree also. We have new caves to survey - the good times are back!
The Goal of a Survey
A surveys goal - in short - is to provide data for the creation of a map of that cave. Sound simple? Well it becomes difficult when you realize we are not mapping a surface, but rather a void inside the earth. We have to represent a space represented by the walls, floor and ceiling only viewable from inside that space. Birds eye techniques do not work underground. And when you add in the rough circumstances of some caves - the water, mud, exposure, and long trips it can only get harder.
Well.....(What is the point of this tirade)
But wait! I am not trying to scare you away! There are some of us who think surveying and mapping a cave is great.
We often bring newer folks to help us on these projects. The truth is some of us rarely recreational cave, and a good percentage of the trips that go out a month are some sort of exploration or mapping. We want to bring you along! Here are some tips and insights to help you understand just what it is we are doing, running around with tapes and pencils and shouting things like " On station!" "Point!","Backsight!".
I don't intend to give all the information you'll need, just enough to understand what is happening. Much better resources exist - such as On Station (NSS Publication) and MSS (Missouri Speleolgy Survey) Introduction to Cave Mapping
Why Survey ?
Why Survey ? This is a question almost everybody asks at one time or another (I usually ask myself when I am in mud up to my tonsils). Long articles have been written to answer this question, but I'll keep it short
We survey to find out where the cave goes. By finding out where the cave runs we can put together a map of the cave. This often helps us to find new passages, or disregard others by seeing how they lie compared to other passages or surface features.
Personal reasons for surveying vary from doing it to be caving, to going with people you enjoy to be with. I survey because the joy of watching a cave you have pushed and explored unfold on computer and under pen can be unparalleled.
So - How Does It Work
A survey is a point to point process. We start at a certain location, called point, or station, and record data that describes the distance to the next location. Simple? Right!
Lets take an example, surveying from point A10 to A11:
First the distance (this can also be called tape). This is done by stretching a measuring tape between the two points, and measuring the distance in feet or meters.
Second, the bearing. This is the angle from A to B measured on a compass. This gives you an angle vs magnetic North. This is how we know what direction the passage is heading.
Third, is the inclination or the vertical angle measured on an clinometer. This is a measurement of the tilt up, or down, between point A and B. This is used later to find how high B is above or below A.
Each set of data is often called a shot (i.e. the shot from A to B)
Dist. I Bearing I Incl. I
12.3 50 -2
Sometime (or more often then not) we check the readings by first measuring from A to B and then we redo the measurements from B to A. This helps us catch errors.
This whole deal is Line Of Sight. This means we can go no further then we can clearly see from one station to another. This is mainly because we have to see the next station for our compass and clinometer, it also assures distance is correct.
Surveying in a cave is almost like surveying outside. Outside long lines connect stations around a piece of property. Inside a cave we are not trying to work around something, but trying to follow the passage, therein lies the problem. Most cave passages (around here at least) wind, twist, turn, interweave, ect. So, unlike the long lines we can take outside, we have to make many smaller ones, as all stations have to be within sight of each other. It is not uncommon to take 5-10 ft. shots, the average is probably 15-20.
Who Are These People Anyway?
A survey usually consists of 3 or 4 people.
The first person is called frontpoint, or just tape. This persons main task is to locate and shine his light from each point, and drag the tape. This is more important then it sounds. He has to pick points that are within sight of the last station, while looking forward to the next to afford the longest shot there. He must often look two or three stations ahead. An experienced frontpoint can cut a bunch of time by locating points that achieve the longest shot, and make it easier for the compass reader to make good shots. A slack frontpoint can make the compass readers life hell, by locating the points in mud puddles, over canyons, or other creative places (sometimes we do this just for fun - Ask John Wisher). Frontpoint shouts the distance measurement to the bookkeeper (this is the only piece of data not double checked).
The Second person is - you guessed it - the Instrument Reader, we usually call this just Compass. This persons job is to read the compass and clinometer and relay it to the bookkeeper. As I mentioned this can be a nerve wracking job when you are lying in a puddle of mud and the bookman insists you've made a mistake (sometimes the hardest part can be restraining yourself from strangling him). This job is straight forward but needs a measure of precision, we usually try to be accurate within 1°-2°. There are several tricks you can pick up by watching others and then trying yourself!
The third and hardest job is Bookkeeper, you'll hear this referred to as simply book or keeping book. It is this persons job to take down all the data being shouted at him, check it for errors, and at the same time sketch the passage so that the details are recorded. This includes a running sketch of the passage, and a series of cross sections, as well as estimating left, right, ceiling, and floor distances. This job can take a lot of work and practice, but we've found artists and draftsman who have taken to it right away. This is one of the more complex and time consuming tasks when surveying, and it is not uncommon to have to wait on the book.
The fourth person, if there is one, is Backpoint, he helps in the checking procedure by lighting the last point (without the fourth, the bookkeeper would do this, but it can tie him down and slow the survey). This person also follows up on leads to help the bookkeeper.
OK, I'm Down in this Hole with you - NOW What?
Now you know what we do, and who does it - the only this missing is HOW. Well it goes a little like this:
From point A the frontpoint moves forward to find a suitable point B. She marks it, warns the compass reader that she's pulling the tape (he holds the other end of the tape at A), pulls, and shouts out the distance. She then sets her light directly on her marked station.
Then the instrument person reads the compass and clinometer from A (where he is) to that light (B), shouting the data to the book.
When he is done he then moves up to B.
The back point moves up to A and sets his light on station. When the compass reader has moved up to B the frontpoint points out where the station is. Then she is free to move on to set up point C.
The Compass reader then reads data back to the light at A. This is where we can check for errors. The bookkeeper checks for errors, and if it checks out the compass reader then shots forward to the new point C that the frontpoint picked.
What is the bookkeeper doing all this time? Other then getting in the way, he is marking down the data, checking and wandering around the passage noting details.
This all sounds complicated and like a ballet, take it from me - it sometimes looks like a demolition derby, but it works and sometimes can roll quite smoothly.
Then What Happens?
The data is taken home to whoever is drawing up the cave. That person reduces the data into X Y coordinates and obtains a line plot. Then he uses the sketches to draw in the cave around the line plot.
This is an ongoing process and cave maps are often in the drawing stage for months or years. Many are never finished, as new discoveries are making existing maps obsolete. New maps are published in newsletters and bulletins.
To Sum Up (The End!)
This takes care of the rough details, so that if you join us surveying underground, you'll have an idea of what's going on and what to do when someone throws a compass your way. And that is exactly what we would like to do - Join Us Underground (You won't forget it, though you may try!)
H.J. Kalnitz J.A.C.K. Ass. #1 NSS 20678