DefineObservers[A,B,a]

DefineObservers[{A1,B1,a1}, ..., {An,Bn,an}]

A,A1, ..., An: names of declared observers

B,B1, ..., Bn: names of declared points

a,a1, ..., an: names of declared triads

The function DefineObservers associates a reference point and a reference triad with a given observer. An observer may only be defined once.

The function DefineObservers results in permanent changes to the global variable GlobalObserverDefinitions.

Restart;
DeclareObservers[A,B,C];
DeclarePoints[Ap,Bp,Cp];
DeclareTriads[a,b,c];
DefineObservers[{A,Ap,a},{B,Bp,b},{C,Cp,c}];
GlobalObserverDefinitions

$\left\{A\to \left\{''Point''\to \mathrm{Ap},''Triad''\to a\right\},B\to \left\{''Point''\to \mathrm{Bp},''Triad''\to b\right\},C\to \left\{''Point''\to \mathrm{Cp},''Triad''\to c\right\}\right\}$

DeclareObservers, DeclarePoints, DeclareTriads, DefinePoints, DefineTriads