Spectra Precision ProMark 800 Reference Manual - Manual (Page 74)

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Precise Surveying - Field Applications & Concepts
The receiver has to correct the collected data (most notably
pseudo-ranges) so that they appear as if they had been
collected –for each frequency– at the virtual phase center, not
at the real phase center.
This implies for the receiver to be informed of the
dimensional parameters of the real antenna used, and the
necessity for it to perform the correction automatically on the
raw data being collected after the “Virtual antenna” function
has been enabled.
Note that in the data conversion, the virtual ARP is
maintained at the same location as the real ARP.
When GNSS antennas are embedded in the receiver (active
antennas such as ProMark 500 or ProMark 800), users don’t
have to enter their characteristics (because they are hard
coded in the receiver).
On the other hand, when an external antenna is used, with
the ProFlex series or with ProMark 100 or 200 for example,
users have to specify which external antenna is used so the
receiver can perform the appropriate correction.
Satellite
Pseudo-range
for Real Antenna
Virtual Phase Center
ARP
Real Phase Center
Pseudo-range
for Virtual Antenna