Antenna measured location, Tallysman

Hello all

I have read the documentations and read some threads on this forum but not found my answer.

Since Reach and the antenna can be used as RTK GPS I would assume it is very important to get accurate actual position on where the location is being measured by the Reach unit. For example on the Trimble antennas there is for an example a grey line that one should measure the height from.
So where within this grey box of the Tallysman antenna is the position being measured? The
height of the grey box is 14.3mm.

Thanks in advance!

@AllenCrawford maybe you have phase center measurement data for TW4721 that you can share?

Thank-you for your interest in Tallysman’s antennas. The ARP (Antenna Reference Point) for the TW4721 is the bottom of the antenna. This antenna has not been calibrated by NGS nor by IGS, therefore there are no .atx files available. The data available on Tallysman’s website shows the PCV measured by an independent lab using a Satimo chamber. Unfortunately, one cannot rely upon the PCO since the antenna wasn’t accurately centred in the chamber.