WIP: Gnss

MR open while Gitflow transition is on.

Set to merge to origin/devel

src/constraints/constraint_autodiff_trifocal.h

@@ -325,12 +325,12 @@ inline void ConstraintAutodiffTrifocal::expectation(const MatrixBase<D1>&     _w
          *   c1Ec2 = [T]x * R        <--- Essential matrix
          *
          * or, if we prefer the constraint P2' * c2Ec1 * P1 = 0,
-         *   c2Ec1 = c1Ec2' = R' * [T]x (we obviate the sign change)
+         *   c2Ec1 = c1Ec2' = - R' * [T]x
          */
         Matrix<T,3,3> Rtr = c1Hc2.matrix().block(0,0,3,3).transpose();
         Matrix<T,3,1> t   = c1Hc2.matrix().block(0,3,3,1);
-        _c2Ec1 = Rtr * skew(t);
-//        _c2Ec1 =  c1Hc2.rotation().transpose() * skew(c1Hc2.translation()) ;
+        _c2Ec1            = - Rtr * skew(t);
+//        _c2Ec1 = - c1Hc2.rotation().transpose() * skew(c1Hc2.translation()) ;
 }
 
 template<typename T, typename D1>