Survex digest, Vol 1 #136 - 3 msgs

Richard Knapp
Thu, 09 Aug 2001 12:03:24 -0400 (EDT)

On Thu, 09 Aug 2001 16:46:00 +0200, Eric Madelaine wrote:

> said:

>> Yes, LRUD are dependant on a shot but there are three ways they can
>> be taken:
>> 	- perpendicular to next;
>> 	- perpendicular to last;
>> 	- average between last and next. 
>If you have a second look to the way this is done in Toporobot, you comme to 
>the idea that the 3 ways listed by Richard are for LR dimensions only.

Interesting. True, the most common method is to apply that to only LR measurements. There is nothing to prevent UD/CF 
measurements from being taken the same way. After all, a shot describes a vector in three-space; UD/CF can be relative 
to it as well.

>In practice, if you have tried to apply this to UD data, you will probably 
>need to specify vertical dimension differently, e.g.:
>	- vertical
>	- bissectrice (average)
>	- horizontal

I like this. It does makes sense. I do have a question about the "bissectrice/average" option. Do you mean the dimensions 
would be an average between horizontal and vertical or based on the surrounding shots? Also, the "horizontal" option is 
a little confusing. If UD measurements are horizontal, how do you differentiate between the various passage dimensions 
when drawing the cross-section? Without a specific "up", it would be hard to determine where LR would go as opposed 
to UD. Granted, the data is still helpful.

	- Richard Knapp

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