Belfry Bulletin

Search Our Site

Article Index

 

Round and About

A Monthly Miscellany

Compiled by 'Wig'

154.      Survey Gradings.  In December 1972, the Surveying Sub Committee set up by the C.R.G. before its amalgamation with the B.S.A. reported its findings in C.R.G. News Letter Number 132.  It said that the majority of cave surveyors were 'of the opinion that because the existing system worked very well and was widely recognised it would be preferable for any amendments to be minor rather than radical changes.  This would have the advantage that the new and modified schemes were at least reasonably compatible.'

The sub-committee (Dave Brook, Bryan Ellis, Trevor Ford, Dave Judson and Gordon Warwick) sounded out surveyors for their comments and views.  The fundamental decision reached was that no longer would grades be based on instruments used but on the required precision for lower grades and accuracy for the higher grades.  The numbering of the grades is unaltered except that there no longer exists a grade 7 but a grade X for any survey not based on magnetic instruments.  The grade X can be of any related accuracy and no longer has to be better than grade 6. The terms 'accuracy' and 'precision' have been defined.  Accuracy is the nearness of the result to the true value and precision is the nearness of a number of readings to each other irrespective of their accuracy.  The new grades are as follows:-

1.                    A sketch of low accuracy where no measurements have been made.

2.                    A sketch intermediate in accuracy between grades 1 and 3.

3.                    A rough magnetic survey.  Horizontal and vertical angles to nearest 50, distances to within 1m.  Station position error less than 1m.

4.                    A survey lying between grades 3 and 5.

5.                    A magnetic survey.  Horizontal and vertical angles accurate to 1O.  Distances accurate to 20cm and station position error less than 20cm. Instruments must be calibrated.

6.                    A more accurate magnetic survey than grade 5.  Compass and clinometer readings up to the present best standard of accuracy of ½O. Distances and station positions to 5cm.

X.                    A survey based primarily on a theodolite.  All grade X surveys must quote an estimate of their accuracy and details of the methods and instruments used.

Why, oh why must we have our national 'specialists' bury their heads in the sand against all reasoned argument?  However, it does seem that the sand was a little loose around their ears as they have now introduced preferred grades and if one looks a little closely at them, one will see that the Mendip surveyor’s arguments have been filtering through.  In the late 1960's, after considerable thought, the Mendip surveyors came to the conclusion that there were only TWO basic groups of survey.  One was a LOW accuracy survey which for want of a better word they called a MAP and a high accuracy survey which they agreed should be actually called a SURVEY.  Even these definitions are unnecessary as the only message that need be put across is that any survey is better than none at all and when you've done it, white a short note on how you did it.  By the way, is your 1” O.S. survey (or map) a map (or survey)?  Is the 25” O.S. a surveyor map?  Pity the sub-committee couldn't see it!

155.      Watch your car.  Car thieves are about on Mendip again.  Recently a visitor to the Mineries Pool had his car broken into and over £120's worth of property stolen.  No longer are the thieves sliding wire through the quarter lights - they are simply smashing them.

156.      No speed limit through Priddy.  The local authorities have turned down a request for a 30 m.p.h. limit through the village.

157.      New Books.  The third hook in the Series ' Northern Caves' (Volume 4) Whernside and Gragareth has made its appearance.  Price £1.20.  At the same price Trevor Ford's 'Caves of Derbyshire' (3rd Edition) makes its appearance.  In the same format as the Northern Caves series, it now includes line surveys of the larger caves in the area.  Small stocks are at the Belfry.  The second in the Series 'Limestone and Caves, published by David and Charles, dealing with Mendip makes its appearance now, after three publishing dates, on April 3rd 1975.  Price £7.50. Tony Oldham's latest offering is a giant bibliography entitled 'Caves of Scotland (Except Assynt)'.  Though there are several caves within the country longer than a thousand feet, the majority are merely short caves and rock shelters. Martin Mills has contributed the section dealing with the Isle of Skye. 174pp, maps, surveys, price £3.00. The dedication is to John Hooper.  ADO states that 'Caves of Devon' is now out of print.

158.      Digging.  The N.H.A.S.A. Windsor Hill dig is continuing on Wednesdays.  The B.E.C. dig has ground to a halt for the next few months. Flower Pot is being reopened and dug in the side passage near the entrance.

159.      Cave Notes.  The next edition will make its appearance later in the year and will include more interesting articles on original work carried out by club members.  Among the items to be considered is John Hunt’s SRT, Graham Wilton-Jones and Bucket Tilbury's 'OFD' and other bits and pieces.

160.      Library Books.  Have you any library books?  If so, will you please return them as soon as possible so that a half-yearly check can be made.

161.      C.S.C.C. Hon. Secretary.  In May this year, Tim Reynolds is resigning as Hon, 'Secretary of the C.S.C.C.  He is looking round for possible contenders for the post.  If you feel that you ought to enter the filed of National caving politics, then chat Tim up as I feel sure he will be interested.

162.      Britain's Longest caves: (including Eire). O.F.D. 23.9 miles (38,500m); Easegill 18.95 miles (30,500m); Aggy 15.41 miles (24,800m); Pollnagollum 7.33 miles (11,800m); Gaping Gill 7.02 miles (11,300m); D.Y.O. 6.96 miles (11,200m); Doolin 6.52 miles (10,500m); Langcliffe 6.03 miles (9,700m); Mossdale 6.03 miles (9,700m); L.N.R.C. 5.09 miles (8,200m); W. Kingsdale 4.72 miles (7,600m); Peak 4.66 miles (7 ,500m).

Answers to Space Filler on page 12

A.         Dave Irwin

B.         Graham Wilton-Jones

C.         Colin Dooley

D.         Barrie Wilton

E.         Alfie Clloins

F.         Chris Howell