From: Michael Lake (mikel_at_speleonics.com.au)
Date: Sun Jan 21 2001 - 12:49:34 CET
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Julian Todd wrote:
> I've done quite a bit of development on this topic.
....
> read in http://www.goatchurch.org.uk/Tunnel/xsecto.html
> This page contains diagrams.
Can't connect to that server but from the describtion below its seems like
there are similarities to what I had thought about.
> It basically gives it in 7 parameters:
> Location: station0_location + lambda * (station1_location -
> station0_location)
> Orientation: angle = (angle(station_fore_location - location) +
> angle(location - station_back_location - location)) / 2 + adisp, tilt_angle.
> Obvious adjustments made to account for one or other or both of
> station_fore_location and station_back_location
> being null.
> Sensible cross sections need not be in the vertical plane,
> or centred on a station. They can be halfway along a leg,
> and be tilted with the general dip of the passage.
This was what I came up with early last year. The idea is taken from geology.
<SHOT FROM="88" TO="88a" AZIM="7.18" ELEV="10" DIST="+44.5" >
This shot was a bit difficult.</SHOT>
<SHOT FROM="88b" TO="88a" AZIM="3.6" ELEV="225" DIST="-55" />
<XSECT>
<XDATA SHOT="88 88a" POS="start">
0.5 2.0 1.5 0.4 </XDATA>
<XDATA SHOT="88 88a" POS="2.0">
0.5 0.8 2.0 0.9 1.5 1.0 0.4 0.9 </XDATA>
<XDATA SHOT="88 88a" STRIKE="30" DIP="-45" POS="end">
0.5 2.0 1.5 0.4 </XDATA>
</XSECT>
A general XSECT element encompasses cross section which is an arbirary shape. The
perpendicular vector from its surface is its STRIKE. If its a cross section that is
perpen to the leg or shot then STRIKE=bearing of the shot, the DIP=elevation of the leg
(and the default if not specified).
Cross section data is stored as character content within [[XDATA]] elements as
sequences of equispaced measurements in the form r1 r2 r3 where 0..theta..360.
Attributes of the [[XDATA]] element specify the orientation of the cross section.
The 3rd cross section above is 2.0 metres along the leg 88->88a
ie the radial distances are in the example above
2.0 2.0
^ 0.8 ^ 0.9
| |
<--0.5 1.5--> <--0.5 1.5-->
| |
| 0.9 | 1.0
0.4 0.4
I think is similar to what Julian had. Will check his website when its up.
Mike
-- -------------------------------------------------------------------- Michael Lake Active caver, Linux enthusiast and interested in anything technical. Safety Convenor, Australian Speleological Federation http://www.speleonics.com.au --------------------------------------------------------------------
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