So - Im part way through drawing up a survey, all going well (tunnel is awesome  :bow: )..

however, I've noticed that one leg on my survex line is incorrect, Easily sorted in Survex, but can I alter my center line within tunnel, Or do I have to import the whole thing again, and somehow overlay it, then re do all my connective lines etc. 

Not sure how to approach it really  :-\

OK, a quick summary of how to update the survey data within a sketch. This applies whether you are correcting an error, or have added new data to an existing survey.

1) Start a new empty sketch.
2) Import the new survex data file into the empty sketch as usual.
3) Import the centreline as usual.
4) Save the new empty sketch with a new filename.
5) In the Tunnel Main Box window, you should now see both your new and old sketch files listed. Select the old sketch file (just select it with a single click, we don't want to open it).
6) Return to the drawing window which should still be showing your new sketch with just the new centreline.
7) Select 'Import down sketch' from the import menu.
8 ) Tunnel should now import the drawing into the new sketch, distorting it to fit the new centreline automatically.
9) You can now continue working with the new sketch file.

Depending on how drastic an error you corrected, you may need to do a bit of tidying up in the sketch were you corrected the data. Loop closure corrections which just tweak the positions of the whole sketch generally work fine. But changing a bearing by 90 degrees in a passage can put a bit of a kink in the passage walls where they get bent to fit the new angles of the centreline. But it doesn't take long to fix up.

righto - that worked, albeit with a bit of a blip -

Error was that I needed to move the final few legs from one station to another.
i.e. survex was
60 - 61
61 - 62.
but should have been
60 - 61
60 - 62.



So followed Footlegs instructions to get new survex line into a new sketch, fine - sorted....



but when I did the 'Import Down Sketch - it seemed to add an extra leg on.



bit odd, I simply enabled the 'delete centerlines' option and deleted the extraneous center line and redrew the sump, but otherwise - sorted  :bow:

Ah yes, this is because by default Tunnel will import any legs from the old sketch that do not exist in the new sketch. In your case this was leg 61-62. This is useful when importing a sketch into a new sketch where the old sketch contains parts of the cave not in the centreline data you created the new sketch with. But in this case you do not want it to happen.

To turn off this behaviour just select the option in the import menu to 'Exclude Centrelines' before you import the old sketch into the new one.

:bow: