[Therion] What is exactly "extended elevation"?

[Bruce]

What is an extended elevation?

Not such a silly question, as I could not find it directly described in the
Therion Book or the wiki.  I think it was described on the forum once, but I
cannot find it now.  It deserves a FAQ entry.

My off the cuff definition...

Imagine the plan view of the cave straightened so that all of the passages
lie on a single line from left to right (or vice versa).
Now imagine viewing this straightened cave from the side - this is an
extended elevation (often called a developed elevation in other packages).
The passages are all shown with their true slope as you would experience it
travelling through the cave.  Very good for producing a route guide
elevation for a vertical cave.

Bruce