How does RS2 differ from Larson's Reciprocal System (RS)?

RS2 incorporates several concepts that are omitted in Larson's RS (which was published in 1959, so some where just not known at the time):

1. The Observer: Larson's RS does not include the assumptions made by the observer and their instruments when trying to observe and measure phenomenon. RS2 includes the observer "assumptions" in order to back-calculate what is really being observed and measured.
2. Reciprocal Geometry: Larson's use of Euclidean geometry was "linear", so he had to construct devices such as a "rotational base" to account for rotational systems. RS2 recognizes that geometry also has its "reciprocals", and the inverse of linear geometry is polar geometry and that rotational motion is a natural consequence of a polar geometry.
3. Projective (Synthetic) Geometry: though Larson postulates "Euclidean geometry", his use of scalar motion as the basis of his theory is not Euclidean in nature--it falls into a different geometric strata known as "affine geometry." RS2 adopted a technique used in the virtual reality systems of computers called "projective geometry", which explicitly defines the relationships and transformations between geometric strata--and how scalar motion (affine) can transform into coordinate motion (Euclidean, which remains a mystery in the RS).

Though some of the natural consequences change with these additions, the bulk of the RS2 system is the same as Larson's original work. It just simplifies a lot of concepts, since conceptual devices can be reduced.