[Therion] Magnetic deviation corrections

[Martin Sluka]

• declination <specification> ◃ set the default declination for all  
data objects in
this survey (which can be overridden by declination definitions in  
subsurveys). The
<specification> has three forms:
1. [] an empty string. This will reset the declination definition.
2. [<value> <units>] will set a single value (also for undated surveys).
3. [<date1> <value1> [<date2> <value2> ... ] <units>] will set  
declination for
several dates. Then the declination of each shot will be set according  
to the date
specification of the data object. If you want to explicitly set the  
declination for undated
survey data, use ‘-’ instead of date.
3 Note: it’s not possible to reference any object from the higher- 
level surveys.
14 If no declination is specified and some geodetic coordinate system  
is defined, the declination
is automatically computed using built-in geomagnetic model.
N.B.: The declination is positive when the magnetic north is east of  
true north.

So if you write declination 0 to particular survey it should work.

m.s.



On 1.11.2010, at 12:06, Graham Mullan wrote:

> Therion appears to correct for mag deviation automatically, based on  
> the date that a survey was carried out. is it possible to turn this  
> feature off within specific surveys? I have much legacy data where  
> either the relevant correction has already been applied or where  
> they have recorded a "compass correction" which includes both  
> instrument error and mag deviation in one figure.
>
> Graham
> --
> graham.mullan at coly.org.uk
>
> 0117 9502556 or 07887 637064 (or 0844 2327803)
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