[Proj] Left- or right-handed rotation convention: which is which?

mikael.rittri at telia.com mikael.rittri at telia.com
Sat Sep 30 12:21:12 EDT 2006

I am confused. 
At my work, I have tried to document the rotation convention used by 
our software for seven-parameter datum shifts.  Since it was originally 
based on publications from the Swedish Land Survey, it uses the 
rotation convention of USA/Sweden/Luxembourg/Australia, as opposed to 
the opposite European/IAG/ISO19111 convention.  

Following http://www.ordnancesurvey.co.
html, I have called the USA-etc. rotation convention the left-handed 
one.  The British Ordnance Survey writes, about the European 

"Beware that two opposite conventions are in use regarding the 
rotation parameters of the Helmert transformation. Equation (3) uses 
the right-hand-rule rotation convention: with the positive end of an 
axis pointing towards you, a positive rotation about that axis is 
anticlockwise. A way to remember this is: if your right-hand thumb in 
hitch-hiking pose is the positive end of an axis, the curl of the 
fingers indicates positive rotation."

But now, I have noticed that the Grids and Datums columns of Cliff 
Mugnier (http://www.asprs.org/resources/grids), at least the columns on 
Finland and the Netherlands, say that it is the American convention 
that is right-handed, and the European one is left-handed.  

Well, I suppose that everyone wants to be right, and no one wants to 
be left!  But are there any simple, unambiguous names for these two 
conventions?  Would the following be correct:
  American convention = "coordinate frame rotation";
  European convention = "position vector transformation".

Is the "Bursa-Wolf" transformation exactly the same as the European 
convention, whereas a "Helmert" transformation is a more general term, 
and can refer to either rotation convention (and, indeed, this kind of 
transformation in n-dimensional Euclidean space, for any n)?

Grateful for comments,
     Mikael Rittri, Carmenta AB, Sweden

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