The well-known EPSG geodetic parameter dataset contains coordinate reference systems (CRS) and their transformation parameters.
A geographic CRS is based on a geodetic ellipsoid approximating the surface of the earth. Geographic coordinates (latitude and longitude) are referenced to a geodetic datum. A geodetic datum defines a particular ellipsoid by a set of parameters, including the semi-major axis and either the semi-minor axis or the inverse flattening.
Models and planned points are referenced to the local CRS and datum used at the site. EPSG codes are used to identify the applicable coordinate transformation parameters as defined by the datum.
GNSS receivers produce WGS 84 coordinates by default. The devices are usually set to display coordinates transformed to the CRS and datum used at the site.
People performing surveys or processing the data must be aware of the CRS and the referenced datum.