[Therion] extend

[Martin Sluka]

Many many years there is the "length of centerline" term for it. It is defined. 

Martin S. 

Odesláno z iPhonu

10. 6. 2018 v 14:33, Marco Corvi via Therion <therion at speleo.sk>:

> i put together comments to all the posts 
> about "extend"
> 
> (1) yes, -1 = left, 1 = right and vert is in the middle (0)
> 
> (2) evaristo, with his proposal of idealized profile not only suggested a way to control shortening, but that also allows stretching. that's good
> 
> (3) bruce described a procedure for a program to automatically decide how to draw splays in the extended profile.
> it's more or less what topodroid implements: at a station the range of azimuths is divided into angular sectors one for each leg at that station. a splay is "projected" using the leg of the sector its azimuth falls in. (by the way, to really be in bad luck one need three vert in a row)
> 
> (4) a program may assign extends to splays automatically, but the user should always be allowed to override what the program does.
> (that's why a user can set extend also for splays, in topodroid)
> 
> (5) "cave length": in the (old) manuals i studied that the cave length is "computed" measuring the length of an ideal line that goes thru the middle of the passage.
> now it is rather cumbersome to compute that line, and all the programs uses the length of the midline, with some discount (duplicate in therion, L in compass, and so on).
> the problem, i think, is that cave length is not a thing that can be well-defined.
> so the numbers we give for cave length are an approximation of a fuzzy concept.
> 
> marco
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