[Therion] North True Grid Magnetic Astronomical?

[Bruce Mutton]

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

Yes Martin,
I have started out on this course and this aspect of Therion is working very
easily.
Thanks heaps.
Bruce