[Therion] Bitmap calibration

[mara]

Hi,

I am having some trouble in calibrating a bitmap image to be used as 
surface layer. I believe this is quite a basic problem but I havn't 
find anything in the archives.
I need to insert data of 2 different points, so entrance of the cave 
is 0 0 and I can get the relevant bitmap pixels data from a software 
like Microsoft Paint. 
Now, the question is how should I get the data for the second point? I 
have no knowledge of where the stations are compared to the surface.
Sorry but I'm really new to coordinates, GIS and all this stuff....and 
wonder how to proceed.

And also, to make sure the scale is correct I should just export tha 
map with same scale as the surface map scanned, is this correct or I am 
missing something?
thanks a lot for yr help
Best
Andrea


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