Online PPP computes the height, as well as latitude and longitude, of the antenna phase centre realised by the processed observations.

In order to obtain the position of the ground marker, the vertical distance between the ground marker and the antenna reference point (ARP) as well as the distance between the ARP and the antenna phase centre (APC) must be known. National Geodetic Survey GPS Antenna Calibration.

The vertical distance between the point to be positioned and the antenna reference point is a function of the antenna installation. If known , the ARP to marker distance in units of metre should be input as the H component of the "ANTENNA: DELTA H/E/N" RINEX header record (see section 1.2.2.1).

Note that the E and N components, even if non-zero, are not considered in the PPP computations at this time.

The distance between the antenna reference point and its phase center is frequency dependent and a function of the electronic characteristics of the antenna. It is usually obtained from laboratory or field calibration and is expected to remain constant among all antennas of a given model and manufacturer. Online PPP uses the antenna phase centre calibration values published by the International GPS Service (IGS) and by the U.S. National Geodetic Survey (NGS). The IGS convention for antenna model identification is used to uniquely identify on the "ANT # / TYPE" RINEX header record the GPS antenna model used at data collection. The same model identification number is also used to retrieve from the antenna phase calibration table the appropriate ARP to ACP values.

The "marker to ARP" and "ARP to APC" distances used for PPP computations are included on the output summary report and should be verified to validate the computed position.