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<title>1990: Cambridge Underground report</title>
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<center><font size=-1>CTS 91.1327/f: Cambridge Underground 1991 pp 28-31</font>
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<h2>Surveying Report Part II - Survey production</h2></center>
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<p align=right>Wookey
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<p>This is an attempt to summarize what I have learned about the art/science
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of survey production, from getting people to do it in the first place,
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through processing the data, to producing and distributing the finished
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product.
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<p>I have only performed this exercise twice so I don't claim to be a great
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expert, but I think it is worth recording the current state of my art (?) to
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give future CUCC surveyors something to work from. Having said that, I
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suspect that much of what I will say will very rapidly become out of date due
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to the extensive use of technology.
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<p>First, never forget that surveying is ultimately pretty pointless, and
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that most of your compatriots have very little interest in surveying for its
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own sake. These people can usefully be bullied and cajoled into going out
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there and getting you some data, but it is fair to say that an uninterested
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surveyor is not likely to produce outstanding work. Bearing this in mind you
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are likely to have to go and do lots of real surveying yourself. You will
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then notice that it is very hard to do well, and that the only reasons you
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understand your stuff any better than anybody else's are a) because you did
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it yourself, and b) because you learned what information you need from having
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to make half of it up the year before.
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<p>It is almost impossible to appreciate exactly what is required to make
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drawing up straightforward unless you have tried it yourself, so any
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opportunity to make your surveyors do some should be utilised (I have largely
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failed in this so far).
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<p>Right, that's enough sermonising.
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<p>Having got yourself some data what do you do with it? Encourage your
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surveyors to follow helpful practices when writing it up in the survey book,
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and then have a look over it. You may immediately find missing information -
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calibration, compass numbers, names, dates, locations etc. This sort of thing
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is often easy to discover so long as it is noticed quickly. Reference to the
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original notes and/or surveyors should clear up most things.
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<p>Next stick it in a computer. If you can do this during the expo it
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obviously helps a great deal with spotting errors and with locating likely
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connections. Collar your surveyor, stick a plan/elevation of their bit on the
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screen and ask "does it look at all like that?" Answers like "No" and "That's
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not my bit" should be dealt with by working out which bits are
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backwards/total bollocks so that this can be allowed for or corrected if
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feasible.
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<p>Current CUCC computer policy is dominated by the fact that our preferred
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surveying software only runs on a C/E/VGA PC, and the club doesn't own any of
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these. This situation is likely to change as we should shortly have some new
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software which should be persuadable to run on lots of things, and hopefully
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someone can eventually be persuaded to give/lend us some suitable kit
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(unfortunately the only offer I have managed to get so far is a Mac, which
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isn't terribly useful). In the meantime we will be using whatever people are
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prepared to take to Austria, or, if no-one does, it will be back to the club
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programmable calculator!
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<p>The software in question in Sean Kelly's Surveyor '88, written for the
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Queen Mary College Belize Expedition (as it unhelpfully tells you every time
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you run it). Make sure that you are using the improved '89 version which has
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had a major bug fixed and will actually do its sums right. (In the correct
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version SVY2POS has two copyright dates on the title screen - the second
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being 12 Nov 89). SURVEYOR.DOC gives instructions on how to use the program,
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which, although both basic and irritating in some respects, is essentially
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very good and does the job. So far as I know there is nothing better
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available, but Olly and I hope to address this as soon as possible.
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<p>Processing the data involves lots of comparing of cave plots with survey
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data and drawings to spot the obviously wrong bits. You can also use the
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errors thrown up by loop closures, but this often isn't actually much help as
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the closures tend be a little on the dodgy side anyway. This is primarily
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caused by 'expedition conditions' but as we are likely to be claiming Grade 5
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it is worth encouraging the best practices possible, and to aim for errors to
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be under 2 to 3%. This is a rough guide, as the relationship between
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permitted error (within a grade) and traverse length isn't linear and so the
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percentage error could be more for long loops, and less for short ones. See
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the diagrams in Bryan Ellis's book.
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<p>Eventually you will have a plot you are happy with (although upon drawing
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up you are likely to discover more errors); and you will be very bored with
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plotting out 'absolutely the final survey', chopping up all the bits of
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paper, and sticking them all together. Unfortunately Surveyor '88 can only
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output onto an Epson compatible dot matrix printer (it might manage some
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slightly dissimilar interfaces but laser printers don't seem to like it at
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all, even when they claim to do Epson emulation. Until a method of getting
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the plots out on bigger bits of paper (eg. in a pen plotter) is created you
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are forced to a great deal of chopping up and sellotaping together of plots.
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This is very time-consuming and is absolutely desperate without access to a
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guillotine.
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<p>You may now come across some problems caused by adding bits to a
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pre-existing survey. Assuming that you haven't decided to change the view you
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should just be able to draw the new bits independently and graft them on to
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the old survey. Hopefully loop closures and discoveries of old errors will
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not have distorted the old stuff so much that this is impossible (as it did
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this year - aligning Adrian's put Yapate 15 to 20m out, for example).
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<p>The plan was to try and have something ready for the BCRA conference so I
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drew each new bit onto its own centreline (as this could be done in a tent
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whilst still on holiday), then traced each bit, reduced them onto acetate,
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and stuck the results onto an A4 acetate copy of the '89 survey. This sort of
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worked, but produced a fairly unhealthy-looking result as photocopying more
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than two layers of acetate produces lots of greyness. It is also a very
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expensive procedure as to get from the original 1:500 to A4 required a
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reduction to 22%. Normal copiers can only reduce to 64% (requiring four
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iterations), and plan copiers can manage 47% (so only requiring two
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iterations but they are much more expensive). To do all this for nine new
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bits of cave in both plan and elevation takes forever, requires the services
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of about six copy shops and is definitely not worth the effort or cost.
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Unfortunately I only realised this whilst half way through this epic process
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and decided that having already invested a fair amount of time, effort,
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money, and petrol, I might as well finish and have something to show for it.
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<p>When drawing the little bits it is helpful to just plot the bit you want
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to draw, but don't forget that you must arrange things so that whilst it is
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plotted on its own, it is still calculated as part of the total net otherwise
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it may 'unspring' significantly giving you an incorrect centre-line to draw
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on.
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<p>Having discovered that the old and new surveys didn't match properly and
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already having traced each independent bit I decided that the best way to do
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the final drawing was to put the Permatrace sheet on top of the final plot
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and then sandwich each transparent bit of cave between them. This allowed
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alignment with the plot underneath (as both top layers were transparent). The
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old master was treated in exactly the same way but each section between loop
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junctions was aligned separately. This worked very well, the only
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disadvantage being that by the time a bit of cave gets to the master it has
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been copied twice (or four times if you count the original as the one done in
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the cave).
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<p>If you are doing a new survey then the whole thing can be drawn on the
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final plot and then traced to make the master. The only disadvantage of this
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is that you have to work with a great big bit of paper lying around for weeks
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- OK if you have the space.
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<p>Obviously other combinations of wholes, sections and tracing could be
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employed - choose according to circumstance, remembering that tracing is
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extremely quick and easy in comparison to drawing originals (except for all
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the bloody rocks).
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<p>I have rather glossed over the bit which is definitely mostly art -
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drawing round a centreline so that the result looks something like the cave.
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There are actually a number of (sometimes conflicting) considerations here.
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Do you want it to be clear which way to travel or to have lots of realistic
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detail? This really depends on who you think your audience is and your own
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preference. I have aimed for authenticity at the expense of simplicity and
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make no claim that it is at all easy to follow!
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<p>A quick note on materials is probably in order here. Use a propelling
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pencil for the first drawings, as it has constant width and a rubber on the
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other end. The master needs to be drawn in pen so that it photocopies. Thick
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lines in 0.35mm, thin lines in 0.18mm. We tried 0.13mm in '89 and things
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tended to disappear on reproduction. If drawing at a very small scale you
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will find that 0.35 is just too thick to be sensible and everything will have
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to be 0.18. The club has Rotring isograph pens in the above sizes which have
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been very reliable and have not clogged up even when left from one year to
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the next. The ink these use is erasable which is obviously incredibly useful
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- but note that it is much easier to rub off just after it has gone down than
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a couple of days later. After being in place for a long time it will never
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rub off perfectly.
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<p>I recommend proper drawing office plastic film (eg. Permatrace) for
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masters as it is 'dimensionally stable', tough, waterproof, more transparent
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than tracing paper, and photocopies better than paper. The disadvantage is
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the cost - nearly £4 per A0 sheet! If using this then use the special
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film rubbers designed to complement it. Also required are a scale ruler (if
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you can't easily do it in your head) and a drawing board (the club doesn't
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own one of these yet).
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<p>So, you now have a complete survey drawn up - practically finished! Wrong.
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You may be halfway through if you're lucky. Doing the cross sections and the
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lettering is unbelievably time-consuming. Until someone can work out a better
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way you are restricted to getting all the names printed and then cutting each
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one out and sticking it on by hand. At least it's better than doing each
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letter individually with Letraset.
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<p>A bit more detail on this process. Use a sans-serif font which is nice and
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solid. Helvetica seems to be the most suitable of the commonly available
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ones. This is easy to do on a Mac, but requires some quite flash software on
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a PC as they have only just noticed that there are fonts other than Courier
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in PC-land. Getting all the names, and a suitable selection of question
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marks, pitches, climbs, vdlbs, too tights, and cross section labels out on
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someone's laserprinter should thus be quite straightforward.
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<p>To align them when sticking them on use sheets of graph paper carefully
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aligned and stuck onto the back of the master to give a grid. Be careful to
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align the text rather than the edges of the bit of paper that contains it. To
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actually do the sticking use the amazing Scotch Magic Tape. This stuff is
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totally photocopier transparent, can be written on and is the right
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stickiness so that you can peel it off again if you get it wrong, without
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tearing anything.
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<p>The tedium of adding text in this way is perhaps a good reason for
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attempting to scan the image into a computer so that a drawing package can be
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used to add the text. If anyone has access to a scanner then perhaps this
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could be tried next year.
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<p>The other 'little' thing remaining to do is the cross-sections (on the
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plan at least). First you have to pore over the survey book again and decide
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which ones you want, weighing various factors like how representative they
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are, which ones can be sensibly fitted onto the plan, and how much
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space/time/enthusiasm you have. Once you have chosen them you must mark them
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all, think of a numbering system, draw them all, and number them all (in two
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places, obviously). This does, of course take forever too, although it is a
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task suited to distribution if you have several helpers, as each can do their
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own bit and they can all be stuck on to the master later.
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<p>Finally, you must get your masterpiece photocopied and reduced to both the
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size people can stick on their walls, and to something that will go in the
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Journal, and Caves and Caving/Descent. This proved to be extremely hard in
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Cambridge, using the Xerox place next to Sainsbury's for the primary
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reduction and a much cheaper copy place on the industrial estate next to
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Tesco on the A45/A10 junction north of Cambridge. Having a slightly better
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quality master this year may have helped but I think it was the copy shop
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which just got it right first time. In Cambridge we had four visits to Xerox
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with several tries each time and lots of Tippex in between.
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<p>So there you are - piece of piss, and it only takes about 200 hours. If
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you'll just form an orderly queue of volunteers for next year....
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<p>P.S. if anyone thinks I am being dim doing things as outlined above, please tell me so. Obviously anything that improves either the quality or the efficiency is welcome.
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<hr />
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<!-- LINKS -->
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<ul id="links">
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<li>Cambridge Underground 1991,
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<a href="../../../jnl/1991/index.htm">Table of Contents</a></li>
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<li>Surveying Report:
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<ul>
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<li><a href="svy1.htm"> 1: Calibration</a></li>
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</ul></li>
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<li>Other 1990 Expedition info:
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<ul>
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<li><a href="index.htm">Index</a> (more detail than in this list)</li>
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<li><a href="log.htm">Logbook</a></li>
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<li><a href="report.htm">Expo Report</a> (Diary)</li>
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<li><a href="cavegd.htm">161 Description</a> to date (ie. 1990)</li>
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<li><a href="162163.htm">Entrances 162 and 163</a></li>
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<li><a href="newent.htm">New Entrances</a></li>
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<li>Bosch Cordless Rotary Hammer <a href="drill.htm">Drill Report</a></li>
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<li><a href="sponsr.htm">Sponsors</a></li>
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</ul></li>
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<li><a href="../../pubs.htm#pubs1990">Index</a> to all publications</li>
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<li><a href="../../index.htm">Back to Expeditions intro page</a></li>
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<li><a href="../../../index.htm">CUCC Home Page</a></li>
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</ul>
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