[Therion] declination

Stacho Mudrak s.m at group-s.sk
Thu Dec 20 16:03:24 CET 2007

According to Wikipedia (http://en.wikipedia.org/wiki/Magnetic_declination)

Declination converts between true and magnetic bearings: True Bearing equals
Magnetic Bearing plus Magnetic Declination. (See

In therion - declination is implemented this way (to avoid confusion), while in

(true bearing) = ((bearing)-(declination zero err))

Thanks for pointing out, we will mention this difference in thbook.

Regards, S.

Quoting Wolfgang Zillig <wolfgang.zillig at web.de>:

> Hi,
> I've just changed one input file from survex format to therion format to 
> get the LRUD data into the model. The declination is corrected manually 
> by "declination xx degree" within the centreline. I've noticed that I 
> had to change the prefix from "-" (minus) to "+" to get the same result 
> as with survex. In survex it is done by "*calibrate declination xx".
> It would be nice to add a comment in the Therion book that declination 
> correction is opposite from Survex.
> Regards
> Wolfgang
> _______________________________________________
> Therion mailing list
> Therion at speleo.sk
> http://www.speleo.sk/mailman/listinfo/therion

More information about the Therion mailing list