Definition of "Nullantenna" and Antenna Type "Nullantenna"
The Nullantenna has an absolute and isotropic characteristic. Hence, the Nullantenna has no PCV. The PCV are reduced to an antenna reference point (ARP) in order to avoid problems arising from a mean phase center (i.e. dual frequency antenna).
Realization "Nullantenna" A realization of a Nullantenna is an actual antenna corrected by absolute PCV with its associated standard deviations.
"Nullantenna" for Absolute PCV The absolute PCV for a Nullantenna are, corresponding to the definition, null for offsets and PCV.
"Nullantenna" for Relative PCV (refering to IGS/NGS Reference Antenna) The relative antenna type Nullantenna (refering to the IGS/NGS reference antenna) is required for consistency with the currently existing relative PCV tables. This can be derived from an absolute PCV calibration of the IGS/NGS reference antenna (i.e. AOAD/M_T).
The PCV of the antenna type Nullantenna relative to the IGS/NGS reference antenna is derived from the AOAD/M_T, SN 404, absolute PCV field calibration in the following manner:
- the absolute PCV are reduced to the IGS/NGS height offsets and horizontal offsets set to zero:
OFFSETS L1=+0.00000 +0.00000 +0.11000
OFFSETS L2=+0.00000 +0.00000 +0.12800
(north, east, height in meter)
- the sign of the PCV is altered compared to the actual absolute calibration
- only the PCV is relevant for the Nullantenna; hence, all offsets are set to null to achieve consistency with relative IGS/NGS calibrations