The explanation of vertical accuracy of P-7 pro or P-10 Pro

According to the technical specs, the vertical accuracy of Columbus P-7 Pro or P-10 Pro GNSS is 15 meters.

I was told by the Columbus engineer, the 15 meters vertical accuracy originates from the GPS chipset technical specs. In the real world tests, the average vertical accuracy is around 5 meters. 

Compared to the 50 meters vertical accuracy of most single frequency GPS/GNSS , the P-7 Pro or P-10 Pro still has great advantages.