[Therion] North True Grid Magnetic Astronomical?

[Martin Sluka]

On 29.7.2008, at 22:48, Bruce Mutton wrote:

> However there are cases where all we have is a paper map, no computer,
> usually no date (well we do have a date within a decade or so),  
> certainly no
> survey data, and where survey practices result in gross errors that  
> swamp
> any probabilistic or systematic ones.

Hi, Bruce,

anyway you may calibrate such paper map (in the same way as the  
sections), add coordinates to the entrance, draw what you have and  
sometimes in the future somebody will resurvey those cave and correct  
your data.

I'm sure this is the main advantage of "therion method". You may  
collect all accessible data and correct them part after part.

Regards

Martin