Verification of GNSS equipment

Speaking in terms of quality it is not sufficient to measure as precisely as possible. You also have to demonstrate that the equipment used is traceable down to well-known and accepted standards. How can that be achieved in terms of global satellite positioning?
Well, I used my measurement equipment in connection with my personal continously operated reference station and the GNSS test point located at Zaberfeld Stausee Ehmetsklinge, with a distance of 8.868,88 meters from my garage. The position of this reference point was certified by Vermessungsamt Heilbronn.
Here are the results of my measurements:

North Latitude Eastern length Ellipsoid height
Certified Value 49,058346944° 8,9124975° 292,21 m
Measurement 49,05835702° 8,91251317° 291,539 m
Difference 0,000021% -0,00017% -0,23%