[Therion] grid alignment rotation

[Ben Cooper]

Graham,
I too have used declination 0 on the "grid-aligned" data.  That's fine when
there is no cs setting; but when cs is used, for example when we integrate
Upper Flood into the Cheddar Catchment project, Therion rotates the survey
by 0.55 degrees to allign True North to Grid North.

How can I tell Therion that my survey is already alligned to Grid North
rather than True North?  Ideally I'd like to do this at the highest level,
rather than at the individual survey level, as there are about 50 surveys
that make up Upper Flood.  

The layout setting of North Grid or North True doesn't help either.  It is
about the alignment of the survey to the grid, and it affects the grid
references of the stations.  The further from the fixed entrance (as the
crow flies) the larger the error of course.
Regards,

- Ben

> -----Original Message-----
> From: therion-bounces at speleo.sk 
> [mailto:therion-bounces at speleo.sk] On Behalf Of Graham Mullan
> Sent: 17 February 2011 11:48
> To: therion at speleo.sk
> Subject: [Therion] grid alignment rotation
> 
> Ben
> 
> We've had similar problems, notably with some of Willie's 
> data where he applied a correction that encompassed both 
> compass error and declination. The result suggested was to 
> insert a line
> 
> declination 0 degree
> 
> which zero's the declination correction. One can then add a 
> line such as
> 
> calibrate compass +11.5
> 
> in our circumstances, not needed in yours where the alignment 
> with grid north has already been made.
> 
> As far as UFS is concerned, it's also worth noting that 
> Therion recognises the local grid so you can use
> 
> cs: OSGB:ST
> 
> Graham
> 
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