Precise GNSS positioning needs a baseline to be measured.
You have to fix two receivers in place in order to define a 3D vector.
RTK mode is extremely fast, even if less …
You can use a Total Station placing it on a point measured with GNSS receiver, in nRTK mode.
In this case you have a 2D precision of around 2/3 cm.
Or, better …
Using two GNSS receivers for a RTK base-rover you need:
a base GNSS receiver;
a rover GNSS receiver;
pole, stands and tripods.
In order to avoid settings issues you may want …