Survex 0.99 prerelease 5

[Andrew Atkinson]

> > 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).
>
> Never, never, never do this.
>
> You might initially get joke survey data which doesn't distort the current
> dataset, but any additional data added to the dataset which
> changes the loop
> closures will mean the joke data no longer fits exactly, and this misfit
> will be distributed back across the rest of the data.
>
> The best approach is to make a leg in the joke survey a "nosurvey" leg -
> such a leg has a FROM station and a TO station and no other data - the leg
> automatically fits the gap between the two stations.
>
The problem of no leg data is as the cave moves so do the length of the legs
joining the joke survey. Wouldn't a neat solution be to make up a survey for
the joke bit of cave but always make sure that it is after a *solve for the
rest of the real cave, then at least the joke survey maintains its original
made up shape.


Andrew Atkinson
--
Secretary, Cave Surveying Group			www.bcra.org.uk/csg
c/o 31, Priory Avenue, Westbury-on-Trym, Bristol. BS9 4BZ. England