Mag dec from date. was Re: Survex 1.1.1 test version uploaded

[Michael Lake]

M.J. Green wrote:
> With cavern understanding dates, would it be possible to put in 
> corrections between magnetic north and grid north based on date?  It is 
> of course not obvious where to put in this general data, or perhaps 
> survex is tending towards processing everything together, and then 
> extracting the data that is required.

The mag declination correction for a given area might not have a linear 
relationship with the date. Sometimes it is given as so-many degrees per 
year on a map but sometimes it's given as a table of values. I'd rather 
have to add a correction explicitly myself than survex guess it for me 
and not realise it. Also if I get the data wrong for a map by entering 
it incorrectly then the mag dec would be wrong too.

my 2c worth.

Mike
-- 
Michael Lake
Chemistry, Materials & Forensic Science, UTS
Ph: 9514 1725 Fx: 9514 1460



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