[Therion] CS and grid alignment

Ben Cooper ben at caver.plus.com
Wed Feb 16 22:08:41 CET 2011


Is there a way of turning off the grid alignment rotation for parts of a
survey when using the CS setting?  My survey is of a cave (Upper Flood) in
the UK using cs OSGB (or EPSG:27700). Some sections have been copied in from
a paper survey that is already aligned to Grid North, while other sections
are new surveys where I have manually specified declination to Grid North.
When turning on the cs setting, I've noticed that the cave is rotated,
because Therion has assumed that my survey is aligned to magnetic North.  
 
I can see two solutions for the new survey section:
1) change all my declination settings to be True North rather than Grid
North.  In this case Therion will apply the final rotation to Grid North.
2) remove all my declination settings and allow Therion to determine these
based on survey date.  
 
Howevver, I'd prefer not to have to edit all the source files and it still
leaves the problem with the old paper survey that I traced.  Is there
something I can do within Therion to turn off the rotation to Grid North
when using the cs setting?
Regards,
- Ben Cooper
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