Survex 0.99 prerelease 5

[Andy Waddington on Survey stuff]

> In my experience, most people never look at the .pos file.
> Those who do look at it are using it for hand-plotting data ...

I use .pos files when I want to know the locations of just a few stations
from a large survey. This happens on several occasions:

1) When I'm adding entrance coordinates to cave descriptions, or depths
below an entrance, or distances of one passage end from some other
(unconnected) part of the cave (to name those bits of cave description
maintenance which quickly spring to mind - there are probably quite a
few others). This is probably my most common usage.

2) When I'm adding *fixes for entrances when building a schema which
isolates underground surveys from the surface data, or for *fixing points
when trying to track down blunders. Some of this need is being removed by
the developments in survex.

3) When I'm trying to compare conventional survey results with other
methods of locating points, such as GPS data.

4) When "inventing" survey data for bits of cave which haven't been
surveyed, but which have some details available (like pitch lengths).
Here you need to know the locations of the two ends in order to invent
"joke" survey data which doesn't distort the rest of the cave when added
to the dataset, but which *does* appear to connect (eg. the "fiction
survey" in 1623/41).

5) When checking that survex data invented by measurement of a printed
survey gives the same coordinates that I measured off the paper. This might
sound pretty spurious, but on several occasions it has proven useful to
invent survex data for caves where we don't have the original survey data,
just so caves explored by others can be seen in caverot.

None of these usages is necessarily "mainstream", but all are much more
easily done with the sort of output you get from a .pos file. For some of
these uses, you probably don't know in advance that you will be wanting a
.pos file, and it is just simpler to have a .pos to hand when the need
arises. I can envisage situations when you no longer have the option of
rerunning survex on the same data (a good reason for keeping the data in
CVS, so you can go back :). Perhaps a separate tool to generate a .pos from
a .3d would be handy if .pos files are not to be generated by default.

Andy