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</o:shapelayout></xml><![endif]--></head><body lang=EN-NZ link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoPlainText><span style='color:black'>Hi Tarquin<o:p></o:p></span></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>> I don't quite understand why asking it to ignore a leg then changing your mind and asking it to draw it anyway, would cause it to then split it at the point you want. I wonder if I will be able to make sense out of that in future.<o:p></o:p></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>I think of extended generation as a trial and error sequential process. <o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>Tell it where to start, then what direction. See what happens.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>At the point where the generation deviates from what you would like, add an instruction, in the correct sequence. See what happens.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>Once that part works OK, look further along the centreline to find the next deviation, and add another instruction. <o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>So it is not changing mind or contradicting previous statements. See sequence below.<o:p></o:p></span></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>>What is makes me wonder is; why doesn't this exist?<o:p></o:p></p><p class=MsoPlainText>>extend break 6<o:p></o:p></p><p class=MsoPlainText>>This could cause a centreline "weakness", and prefer (but not mandate) breaking at that point. It would massively simplify this control, and be much more predictable.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>This is pretty much exactly what ‘extend ignore 6 <station at other end of leg>’ does. It causes the centreline to break at station 6, and continue automatic extended centreline generation elsewhere.<o:p></o:p></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>Here is the plan view, and the solution I came up with. There are probably others.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><img width=196 height=318 style='width:2.0416in;height:3.3125in' id="_x0000_i1030" src="cid:image001.png@01D59868.2A048E20"><o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'>survey extendedloop<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> centreline<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> data normal from to length compass clino<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 1 2 1 0 5<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 2 3 1 0 -5<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 3 4 1 45 -10<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 4 5 1 90 5<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 5 6 1.71 225 45<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 6 2 1.71 225 -45<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> 5 7 1 90 0<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> <o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend start 1<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend right 1<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend ignore 6 5<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend right 6 5<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> endcentreline<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'>endsurvey<o:p></o:p></span></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><span style='color:black'>Stepping through the process I take;<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend start 1<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend right 1<o:p></o:p></span></p><p class=MsoPlainText>This produces an extended centreline that propagates 1 2 6 5 4 3 2, and now that the loop is closed (and broken at 2), propagation continues for the rest of the cave from 5 7.<o:p></o:p></p><p class=MsoPlainText><span style='color:black'><img width=391 height=176 style='width:4.0729in;height:1.8333in' id="Picture_x0020_1" src="cid:image004.png@01D5986C.5382AB20"></span><span style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>Could I have predicted this sequence? No. Usually I think Therion chooses the surveyed sequence, but not always. This is why I use a trial and error approach.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>From the diagram above, I think that I want the map-connection line (the break) at station 6, and the extended generation direction for the leg to ignore is 6 5 (despite the survey data enumerating this leg as 5 6). So now I try;<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend start 1<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend right 1<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend ignore 6 5<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><img width=385 height=158 style='width:4.0104in;height:1.6458in' id="Picture_x0020_2" src="cid:image006.png@01D5986C.5382AB20"></span><span style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>This is much better, but the leg 5 6 is extending right and not left.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>The apparent generation sequence is now 1 2 6, 2 3 4 5 6, 5 7<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>So I could try;<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend right 6 5<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>or<o:p></o:p></span></p><p class=MsoPlainText><span style='font-family:"Arial Narrow",sans-serif;color:black'> extend left 5 6<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>I chose the former because it involved less typing, but the latter makes more sense perhaps if you are following the apparent sequence of generation. It turns out that they both work, and produce this (same apparent generation sequence, just the extend direction differs for 5 6);<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><img width=371 height=150 style='width:3.8645in;height:1.5625in' id="Picture_x0020_3" src="cid:image010.png@01D5986C.5382AB20"></span><span style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>Don’t worry, extend is a mystery for me as well.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>This example turns out to fairly straight forward, but it can be very complicated for a real cave, especially if you don’t start thinking about the extended elevation until you have 10 km of passage in your project.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>Any further insights greatly appreciated.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>Bruce<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>PS: I just noticed on page 25 of the Therion Book, that extend directions can be explicitly influenced from within a scrap drawing.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><img width=624 height=50 style='width:6.5in;height:.5208in' id="Picture_x0020_4" src="cid:image011.png@01D5986B.DA9295E0"></span><span style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>I’d be interested in finding out about usage scenarios.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p></div></body></html>