Interactive extended elevations

[Phil Underwood]

On Sun, 18 Jun 2000, you wrote:
>Phil Underwood wrote:
>
>> I'm currently working on yet more bells and whistles for chasm.
>> In this case, a slightly more intelligent extended elevation processor=
=2E
>>=20
>> If I recall correctly, there was a discussion on this a while back; th=
is
>> would be my implementation=20
>
>I produced a partial implementation of extended elevations about a year
>ago.  However, it used the pre-loop-closure data, rather than the closed
>data, and I haven't had time since to sort it out.
>
>My implementation used extra commands in the survex file; doing it
>graphically could certainly be advantageous.
>
>I can let you have the code if you think it would be useful.
Thanks - that could be helpful.
>
>> A selectable starting point.
>> Process consequent legs from left to right.
>> Individual legs can be *breakable* and/or *reversed*
>> Specification of several continuous legs, which will be extended as a =
whole=20
>
>Discussion of projecting a series of legs (rather than straightening the=
m
>out) snipped.  This is a useful feature, but a bit of a side point.
>
>> If a loop contains no breakable legs, then it will be broken at a
>> junction, which is unspecified.
>
>I think a warning should also be given in this case, so that the user kn=
ows
>(s)he should choose a more intelligent break point.  BTW, IMO it normall=
y
>looks best if you don't break at a junction.
Agreed.
>
>> If a loop contains one *breakable* leg, then it is broken at that leg.=
 If it
>> contains more than one, it will be broken at one of them (unspecified)=
=2E
>
>In the latter case, I think a warning should be given again.
Also agreed.

>
>> On encountering a *reversed* leg, the direction of unfolding is revers=
ed.
>
>Do you mean just that leg is reversed, or from then on?  I hope the latt=
er:
>you really want to be able to reverse a section of survey easily.
Definitely the latter.
>
>> The graphics interface will allow selection of the starting point,
>> modification of the properties of legs(breakable/reversible), and disp=
lay
>> of legs according to their properties (breakable & broken, not breakab=
le
>> but broken anyway, reversed)
>
>You also want to be able to specify that certain legs should be omitted
>from the extended elevation, for clarity.
OK - I'll include that possibility; the underlying data structures are
already available.=20

>
>> The specification of which legs are to be breakable or reversed is don=
e
>> after processing (ie there would no added survex commands)
>>=20
>> Having rambled on at length about this, does anyone have any better
>> ideas/improvements? Can anyone see any potential problems with this?
>
>One thing that wasn't clear from the description is how the EE informati=
on
>is subsequently stored.  I hope you're planning to store it in a way tha=
t
>it can be retrieved, and such that it can still be applied to surveys on=
ce
>extra data has been added.

It will be stored in the 3dx format; that isn't a problem, both the
positions of each station in extended elevation, and the details as
described above. Chasm also allows you to add colouring information to th=
e
3dx file. However, when the survex files are reprocessed by cavern, all t=
his
added data is lost. I'm working on a text file format, which would hold t=
his
addded data, and can then be merged into the pristine data file.

>
>Gavin
>
>
>--=20
>Survex http://lists.tartarus.org/mailman/listinfo/survex
--=20
Phil Underwood <furbrain@furbrain.screaming.net>
Homepage: http://members.xoom.com/bighairyone/
"It's not what you've got, it's how you make it explode."