how to optimization of the control network
in case of a so called free network adjustment, the point types "new point" and "datum point" are valid. "Reference points" and "stochastic points" cannot be combined with "datum points".
The coordinates of "reference points" are known beforehand. These coordines will not be adjusted. "Stochastic points" are known positions having variances. These points are used within a so called dynamic network adjustment.
Depending on your network design, you can combine datum and new points (free network) or reference/stochastic and new points, if you like to adjust the network w.r.t. a known reference frame.
applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences