guidelines for authors of cave surveys

[Wookey]

On Fri 25 Oct, David Gibson wrote:
> A while ago, I think it was Graham Mullan in this mailing list or over
> in Survex, who was asking about graphics formats, and I made the comment
> that sending a magazine editor a small compressed JPG file for a cave
> survey, as some people apparently do, and expecting them to be able to
> reproduce it at a high quality was .. ummm. [sentence too long,
> truncated].

> Anyway, I now find myself in the position of being a caving magazine
> editor <http://bcra.org.uk/pub/speleology/> and I wondered if the
> readers of this mailing list would like to get together to draw up a
> list of 'guidelines for authors of cave surveys'?  Not just for me - it
> will be useful generally.

> I have put some draft notes at
> http://bcra.org.uk/pub/speleology/format.html>,
> scroll to the section on 'Graphical Content'.

A small correction:
'to narrow'-> 'too narrow'

Your suggestion of separate text-in-drawing-package and paper survey is an
interesting one, but I would expect such a scheme to be fraught with error
unless both the paper image and the file have registration marks. Relying
on correct scale is a) problematic and b) tells you nothing about the
position of the text over the drawing.

You mention EPS saying that import of it is 'dodgy'. I really do think that
you need to be able to read postscript and eps diagrams. It is the father
of all vector formats and anyone using anything unix-derived can always get
postscript out of it, but may stuggle to get anything else you can read. It
is also hand-editable (at least for reasonably simple diagrams), which
means you can fix a problem without access to the producing application,
which is something that is ture of almost no other format. SVG is another
vector format worth recommending as it is intended to become a web-standard
for this sort of thing. It's currently rather too new to be widespread
though.

In practise there is no real standard for vector images outside
postscript-for-unix. You may find the best thing to do is ask people to
send it in every format they can save it as and see which ones come out
best at your end :-)

For scanned cave surveys it's worth pointing out that they are _extremely_
compressible. a PNG or GIF (boo, hiss) will be something like 5% of the
size of the scanned bitmap. In our experience reducing them to 4-colour
(2bit) greyscale (for B&W surveys) produces sharp images with black blacks
that compress excellently. A 256-grey (8bit) or higher scan just has a lot
of fuzziness round the edges of lines, non-white background and compresses
much less well. Obviously colour surveys will need more colours.

HTH

Wookey
-- 
Aleph One Ltd, Bottisham, CAMBRIDGE, CB5 9BA, UK  Tel +44 (0) 1223 811679
work: http://www.aleph1.co.uk/     play: http://www.chaos.org.uk/~wookey/