SNAP can be used to do height adjustments. However if the adjustment includes zenith distance data you will require accurate horizontal positions for the stations. This is because the height difference derived from zenith distance data depends upon the distance between the stations, which in turn depends upon their coordinates.
If you do not have accurate locations you can do a 3d adjustment and "float" stations horizontally. By doing this the uncertainty in their positions is reflected in the derived elevations. Note that doing this will affect that statistics, as the trial horizontal positions of the stations are treated as observations.