Interactive Extended Elevations

[Andy Waddington on Survey stuff]

> extra commands in the survex file

Here we go again ...

There should be no commands in a survex file. Survex's format describes a
survey, not what to do with it. Anything which describes the data, like an
estimate of how accurate it is, is part of the survey. Anything which says
how to display it or process it is a separate issue and should be in a
separate file.

This also has the advantage of allowing you to provide *different* extended
sections from the same basic data. If you have a complex cave (like KH, for
an obvious example) then an extended elevation is a good way of showing a
particular route, with some of the passages leading off. If there are several
routes through/across an area, then its useful to have a different EE to
emphasise each one, and perhaps to accompany the narrative description.

> You also want to be able to specify that certain legs should be omitted

It may be a lot more sensible for the file describing the extended elevation
to list *all* those survey legs which are to be *included*. This makes it a
lot clearer for the human user coming along to edit it, given that these
directives are in a separate file from the original survey data.

Andy