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| extend [2020/10/10 21:05] – [Enumerating extend station sequence] add sample log extend transcript brucemutton | extend [2024/01/24 08:42] (current) – extend options - add tips about making resilient to new loops brucemutton |
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| * They must be followed either by a valid survey **<station>** id, a valid survey **<leg>** (pair of stations), or in the case of ignore, possibly a three station **<path>**.\\ | * They must be followed either by a valid survey **<station>** id, a valid survey **<leg>** (pair of stations), or in the case of ignore, possibly a three station **<path>**.\\ |
| * Generally specifying a **<leg>** applies the option to ONLY to that leg, and specifying a **<station>** applies the option to the leg(s) used to reach (create) that station, AND all subsequent **<legs>** within the centreline (but this might not apply for ''start'', ''hide'', and perhaps ''ignore'').\\ | * For **direction** options, specifying a **<leg>** applies the option to ONLY to that leg, and specifying a **<station>** applies the option to the leg(s) used to reach (create) that station, AND all subsequent **<legs>** within the centreline (**Control** options ''start'', ''hide'', and ''ignore'' apply only to or at the <station> or <leg> specified).\\ |
| * Note that Therion differs from Survex here. Survex applies the **<station>** option only to the subsequent legs.\\ | * Note that Therion differs from Survex here. Survex applies the **<station>** option only to the subsequent legs.\\ |
| * Therefore to help with readability and cross platform usage, it is a good approach to specify two lines, one saying to apply the option to the initial leg where it is wanted, and one saying to apply the option to the (second) station to trigger the automatic propagation. ie | * Therefore to help with readability and cross platform usage, it is a good approach to specify two lines, one saying to apply the option to the initial leg where it is wanted, and one saying to apply the option to the (second) station to trigger the automatic propagation. ie |
| ''extend <0 – 200> <station>'' - stretch or shrink the leg creating this station by the ratio and continue generating all subsequent legs with that ratio.\\ | ''extend <0 – 200> <station>'' - stretch or shrink the leg creating this station by the ratio and continue generating all subsequent legs with that ratio.\\ |
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| ''extend ignore <path>'' - where <path> = station1 station2 station3\\ | ''extend ignore <path>'' - where <path> = station1 station2 station3. The map-connection break will occur at station2\\ |
| ''extend ignore <leg>'' - generation of extended centreline shall not take this leg (or path), it will take the (an)other leg (or path) if possible.\\ | ''extend ignore <leg>'' - generation of extended centreline shall not take this leg (or path), it will take the (an)other leg (or path) if possible. The map-connection break will occur at the first named <station> of <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 onward, or it may offset the leg to a random location (in which case ''extend hide'' may be of use. | * If the leg is part of 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 onward, or 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, 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. | * 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 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.\\ | 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 or more legs past a junction in the direction of generation. ie The generation of extended centreline shall not take this leg, but take another one instead. The map-connection break will occur at <station>. A bug in this functionality was resolved with Therion version 094ac85 14Nov2019.\\ | ''extend ignore <station>'' - where <station> is one or more legs past a junction in the direction of generation. ie The generation of extended centreline shall not take this leg, but take another branch instead. The map-connection break will occur at <station>. A bug in this functionality was resolved with Therion version 094ac85 14Nov2019.\\ |
| 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). \\ | 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”.\\ | <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”.\\ |
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| ''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 or splays. Stations that form the leg remain visible! Does not hide subsequent stations or legs. \\ |
| ''extend hide <station>'' - hides the station and all leg centrelines (usually two of these) that emanate directly from THIS station. It may not hide subsequent stations or legs, something yet to verify. \\ | ''extend hide <station>'' - hides the station and all leg centrelines (usually two of these) and splays that emanate directly from THIS station. It does not hide subsequent stations or legs. \\ |
| Note that the centreline generation is carried out as per normal, the stations and legs are just made ‘not visible’.\\ | Note that the centreline generation is carried out as per normal, the stations and legs are just made ‘not visible’.\\ |
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| * Don't miss Martin Sluka's [[tips#how_to_export_correct_extended_elevation_from_zig-zag_centerline|hot tip for obtaining realistic extended centrelines]] from zig-zagged survey data (uses ''data nosurvey'') | * Don't miss Martin Sluka's [[tips#how_to_export_correct_extended_elevation_from_zig-zag_centerline|hot tip for obtaining realistic extended centrelines]] from zig-zagged survey data (uses ''data nosurvey'') |
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| | * Creating a new loop (such as adding a new survey or using nosurvey legs to straighten a centreline) will often require a significant rework of the extended centreline definition. |
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| * Caves, or parts of caves that comprise a linear passage with one or two dead-end branches are easiest to generate extended centrelines for. | * Caves, or parts of caves that comprise a linear passage with one or two dead-end branches are easiest to generate extended centrelines for. |
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| * Caves with one or more loops are more challenging. The rate of complexity increase is perhaps closer to geometric than linear. It is definitely better to start creating the extended centreline when the cave is only one or two surveys long. | * Caves with one or more loops are more challenging. The rate of complexity increase is perhaps closer to geometric than linear. It is definitely better to start creating the extended centreline when the cave is only one or two surveys long. |
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| | * Therefore it is better to over enumerate (list every leg) to begin with, as this makes the extended network more resilient to the addition of future loops. |
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| ===Creating links between separate caves that are close to each other=== | ===Creating links between separate caves that are close to each other=== |