The Dayton Underground Grotto
of the National Speleological Society
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The Dayton Underground Grotto
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Comments on Cave Surveying by Bill Walden Taken from the November 2001 COG Squeaks Newsletter
Instruments Compass Used to determine bearing in degrees. Two are used -- one for a forward reading and the second for a back sight. The two readings should agree. The Central Ohio Grotto records both the front sighting and back sighting as if they were both front sightings – in the direction of the survey. Clinometer Used to determine the inclination or declination in degrees. Normally only front sights are taken. Tape Used to measure the distance from one station to the next. The readings may be in any units but feet are the most common. Some tapes are graduated in feet and inches while others are graduated in feet and tenths of a foot. Use of either is OK but should be the same for a given survey series. Jobs Point: The surveyor responsible for this position must locate the forward station such that it is as easy as practical to read the instruments and tape. The point station should also be located
such that it is as easy as practical to read the tape and instrument to the next station that has not yet been set. The caver with this job takes the compass back sight (from the point to the from station). The point person is responsible for carrying the tape reel and reading the distance between the from station and the point, and for measuring (or estimating) the cross section dimensions of left, right, top, bottom. From Station The surveyor responsible for this position must ensure that the tape is clear between the point and from station – the tape must not be touching anything between the two stations. This surveyor is responsible for taking the front bearing with his compass and for measuring the declination or inclination with the clinometer. Note taker This job is often assigned to new comers or cavers with little survey experience. It is a very important job! The data must be accurately and clearly recorded. The data must be easily read by the person entering the data from the survey cards or survey note pages. The note taker must repeat the reading give to him by the point surveyor and the from station surveyor and when necessary remind a surveyor to give information. For example the point person may forget dimensions. The note taker must remind him of this task. The data that must be taken include: from station, point station (identified by numbers and letters such as P13 or A26), tape, Front compass reading, back compass reading, clinometer (be sure to include the + for up angles and the - for down angles), and the dimensions of left, right, top, and bottom. Make the point person give these dimensions in the order in which they are recorded on the header of the card or note page. The note taker is responsible for recording the following on the first card or page of the survey: personnel and the job they are doing, date, survey series, cave, distance units used (feet and inches or feet and tenths) and for recording the page numbers on the cards or pages. [Never mix distance units in a survey series.] Sketch In the Central Ohio Grotto we do the sketch to scale. This scale may depend on the size of the cave but most of the time we represent 50 feet by one inch. A Silva Ranger compass is most handy for this important job. One of the primary reasons for sketching to scale is to provide a real time check of the data. A reversed compass reading is readily apparent. In passages that are large enough, it is useful to leave the tape between the two stations while the sketch person does his job. With the tape in place, the sketch person can use it to place objects in the correct position along the passage. Number of surveyors on a team: Two is minimum and four is optimal while three is probably most efficient for most surveys. With 2 or 3 cavers some must do multiple jobs. Go survey a cave! Bill Walden |
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