Interactive Extended Elevations

[Olly Betts]

In message <395250FB@Survex@pennine.demon.co.uk>, Andy Waddington on Survey stu
ff writes:
>>> list *all* those legs which are to be *included*
>
>Olly> If you update the survey you're likely to want the new legs to
>      appear in the extended elevation by default. ... there are likely
>      to be far fewer legs excluded than included ...
>
>I strongly disagree. If you are doing something like an EE of a route
>through a complex cave, it is likely that only a small subset of the legs
>would be needed. If I update the survex data by adding a survey nowhere near
>this route, I don't want to have to go to my EE-descriptor and say "exclude
>these (new) legs which you didn't know about before, and don't need to know
>about now."

This would mean the file would need to list every single leg in the survey
with an "in" or "out" status.  You clearly have in mind a very different
file format to me.  I'm thinking of a fairly small file which says:

 * where to start (by default some likely high up and/or fixed point would
   be picked)

 * where to force folds (by default heuristics would decide where to fold by
   looking at the trends in angles between survey legs)

 * where to break loops (again heuristics can make a default stab)

 * where to prune - legs/traverses beyond which whole areas of survey should
   be removed

This is easy to apply to a newer/older version of the same survey.  Listing
individual legs makes this task much harder.

>If the new bit of survey happens to relate in some way to the particular bit
>of cave that I'm showing on my EE, then I probably want to review the
>descriptor and decide whether to include some or all of the new survey and
>perhaps miss out some of the existing survey.
>
>[...]
>
>As a concrete example - suppose I had prepared an extended elevation of the
>various Left Hand Routes (LHR, Powerstation, Drunk & Stupid, Pitch-Ramp) to
>show their relationships. Then Expo 1999 goes off. If I had listed legs to
>be excluded, then on expo's return, 2.5 km of completely unrelated stuff in
>Chile would suddenly appear. This I would find undesirable.

This isn't a good example - the new data in Chile would be excluded
automatically because it is only connected to the left hand route by
traverses which are themselves excluded.

And if someone added a new survey connecting to the left hand route area you
most likely would want to include it.

The only slightly tricky case I can see is where a connection is made back
to the EE from excluded survey (e.g. ambidextrous, which connected the right
hand route back to the left hand route a couple of hundred metres below
where they originally split.  But that can be detected automatically (using
a node colouring algorithm) and the user prompted about what to do.

Cheers,
Olly