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extend [2018/05/03 11:13]
brucemutton [Extended elevation scrap drawing considerations]
extend [2019/01/14 09:25] (current)
brucemutton [Summary of all extend options, for survey centrelines] independent splay control
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 There should only be one '​start'​ specification I think, but there seems to be no ill effect if there are multiple starts.\\ There should only be one '​start'​ specification I think, but there seems to be no ill effect if there are multiple starts.\\
 \\ \\
-''​extend right <​leg>''​ - extend this leg only, to the right, then continue extending subsequent legs, left or right, as per the leg immediately previous.\\ +''​extend right <​leg>''​ - extend this leg only, to the right, then continue extending subsequent legs, left or right, as per the leg immediately previous. ​ But sometimes it continues generating all legs, as per the next entry below!\\ 
-''​extend right <​station>''​ - continue generating all extended centreline legs from this station onwards, towards the right. ​ Usually this option will not work as described, unless it is preceded by one or two extend right <leg> statements.\\+''​extend right <​station>''​ - continue generating all extended centreline legs from this station onwards, towards the right. ​ Usually this option will not work as described, unless it is preceded by one or two ''​extend right <leg>'' ​statements. ​ And sometimes it can appear to extend the wrong way.  If this happens, use ''​extend ... <​leg>''​ rather than ''​extend ... <​station>''​\\
 ''​extend left <leg> or <​station>''​ - same as for extend right, but extending left!\\ ''​extend left <leg> or <​station>''​ - same as for extend right, but extending left!\\
 \\ \\
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 ''​extend reverse <​station>''​ - continue generating all extended centreline legs from this station onwards, in the opposite direction to the leg immediately previous.\\ ''​extend reverse <​station>''​ - continue generating all extended centreline legs from this station onwards, in the opposite direction to the leg immediately previous.\\
 \\ \\
-''​extend vertical <​leg>''​ - do not extend this leg horizontally,​ extend only the vertical component of this leg, then continue extending subsequent legs as per leg immediately previous.\\+''​extend vertical <​leg>''​ - do not extend this leg horizontally,​ extend only the vertical component of this leg, then continue extending subsequent legs as per leg immediately previous. ​ The order of stations in your vertical statement should usually match the direction of extended elevation centreline generation. However if Therion seems to ignore this vertical statement, try reversing the order of the stations in your vertical statement, and it might work!\\
 ''​extend vertical <​station>''​ - continue generating only the vertical components all extended centreline legs from this station onwards.\\ ''​extend vertical <​station>''​ - continue generating only the vertical components all extended centreline legs from this station onwards.\\
 \\ \\
 ''​extend ignore <​leg>''​ - generation of extended centreline shall not take this leg, it will take the (an)other leg if possible.\\ ''​extend ignore <​leg>''​ - generation of extended centreline shall not take this leg, it will take the (an)other leg if possible.\\
-  * If the leg is an open branch (does not loop back to the main centreline),​ then this has the effect of hiding the entire branch from this leg onwardsat this leg. +  * If the leg is an open branch (does not loop back to the main centreline),​ then this may have the effect of hiding the entire branch from this leg onwardor it may offset the leg to a random location (in which case ''​extend hide''​ may be of use
-  * If leg is part of a loop, a loop connection gap, with joining map-connection line will be formed between two instances of the first station in the leg specification. +  * If leg is part of a loop, it beaks the loop.  ie a loop connection gap, with joining map-connection line will be formed between two instances of the first station in the leg specification. 
-The order of stations in your ignore statement should usually match the direction of extended elevation centreline generation. ​ However if Therion seems to ignore ​this ignore statement, try reversing the order of the stations in your ignore statement, and it might work!  Sometimes the leg specification needs to follow the direction of survey, if it differs from the current direction of extend generation.\\ +The order of stations in your ignore statement should usually match the direction of extended elevation centreline generation. ​ However if Therion seems to ignore ​your ignore statement, try reversing the order of the stations in your ignore statement, and it might work!  ​In any case, try reversing the order to get a different effect (loop connection gap arrangement). ​Sometimes the leg specification needs to follow the direction of survey, if it differs from the current direction of extend generation.\\ 
-''​extend ignore <​station>''​ - where <​station>​ is one leg past a junction in the direction of generation. ​ The generation of extended centreline shall not take this leg. I have found this syntax unreliable, and the following may explain ​why. Marco Corvi says (if I understand correctly) this does not work where there are only three legs meeting at a junction ie the usual case.  So only for use where 4 or more legs meeting at junction(?​).+''​extend ignore <​station>''​ - where <​station>​ is one leg past a junction in the direction of generation. ​ The generation of extended centreline shall not take this leg. I have found this syntax unreliable, and the following may offer an insight as to why. Marco Corvi says (if I understand correctly) this does not work where there are only three legs meeting at a junction ie the usual case.  So only for use where 4 or more legs meeting at junction(?​).
 Also do not use this syntax where <​station>​ IS the junction station, obviously that will have unpredictable results. \\ Also do not use this syntax where <​station>​ IS the junction station, obviously that will have unpredictable results. \\
-Extend ​break is mentioned in some Therion posts, presumably as an alias for extend ignore (Survex terminology). ​ It will trigger a Therion error “unknown extend flag – break”.\\+Try to avoid ''​ignore''​ing the same looped passage (ie an oxbow) at each of its junctions to a main passage. ​ This can have the effect of offsetting the whole oxbow to the far end of the map (which of course is undesirable). \\ 
 +<​del>''​extend ​break''</​del> ​is mentioned in some Therion posts, presumably as an alias for extend ignore (Survex terminology). ​ It will trigger a Therion error “unknown extend flag – break”.\\
 Sometimes branch centrelines will be ignored (hidden?) by default, and an extend right (or similar) statement will be required to stimulate it’s generation.\\ Sometimes branch centrelines will be ignored (hidden?) by default, and an extend right (or similar) statement will be required to stimulate it’s generation.\\
 +\\
 +//There is a lot about ''​extend ignore''​ behaviour that I do not understand and cannot explain. ​ If anyone has insight or explanations for odd behaviour, please amend this page or post on the forum.// \\
 \\ \\
 ''​extend hide <​leg>''​ - hides the centreline part of the specified leg only, but NOT its stations. ​ Stations that form the leg remain visible! ​ Does not hide subsequent stations or legs. \\ ''​extend hide <​leg>''​ - hides the centreline part of the specified leg only, but NOT its stations. ​ Stations that form the leg remain visible! ​ Does not hide subsequent stations or legs. \\
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 ===General Tips=== ===General Tips===
-  * Remember to comment out all extend options in the trip surveys ​before creating a separate extended elevation centreline. ​ I put mine in it’s own file and call it something like Extend-CaveName-ElevEXT.th file.+  * Remember to comment out all extend options in the trip survey files before creating a separate extended elevation centreline. ​ I put mine in it’s own file and call it something like Extend-CaveName-ElevEXT.th file
 + 
 +  * Using this approach, splay shots cannot be controlled (because they have no unique name) independent of the survey legs that they are associated with ie extending a splay left when the legs at that station are extended right. ​ Somewhat contrary to the above point, it seems that you may be able to extend the splays '​in-line'​ with the survey data, in a trip survey file, so long as you take care not to try to also control the survey legs
  
   * Sometimes, if generating the centreline against the direction of survey, then every <leg> needs to be enumerated, ie they don’t autogenerate if just a single <​station>​ is specified. ​ Other times, they autogenerate nicely.   * Sometimes, if generating the centreline against the direction of survey, then every <leg> needs to be enumerated, ie they don’t autogenerate if just a single <​station>​ is specified. ​ Other times, they autogenerate nicely.
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 ====Extended elevation scrap drawing considerations==== ====Extended elevation scrap drawing considerations====
-If you have drawn a scrap with the opposite orientation to the extended centreline generation, it will tend to plot inside out.  You need to compensate for this by including ''​-flip horizontal''​ in the definition of your scrap. ​ Or you can add ''​-revise scrap-id -flip horizontal''​ in your Extend-CaveName-ElevEXT.th file.+If you have drawn a scrap with the opposite orientation to the extended centreline generation, it will tend to plot inside out.  You need to compensate for this by including ''​-flip horizontal''​ in the definition of your scrap. ​ Or you can add ''​-revise scrap-id -flip horizontal''​ or ''​-flip none''​ in your Extend-CaveName-ElevEXT.th file.
  
 If you include in your scrap drawing a ''​point station -name <​station>''​ where that <​station>​ is at a survey leg junction AND is offset in the extended centreline due to extended loop misclosure, then it will force the extended station to plot, incorrectly,​ in its original location, distorting the scrap in the vicinity of that leg.  This can be vexing, as \\ If you include in your scrap drawing a ''​point station -name <​station>''​ where that <​station>​ is at a survey leg junction AND is offset in the extended centreline due to extended loop misclosure, then it will force the extended station to plot, incorrectly,​ in its original location, distorting the scrap in the vicinity of that leg.  This can be vexing, as \\
  • extend.1525338819.txt.gz
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  • by brucemutton