RTN Corrections - Antenna Height Reference Point

[Jim Frame]

When J-Field receives correction data from an RTN mountpoint, does it have any way of knowing whether the height reference is the ARP, the geodetic monument, the APC, or some other measurement point at the antenna? Is that information encoded in the RTCM message, or is there just an assumption that it's (probably?) the ARP?

 

[Jim Frame]

The reason I ask is that I'm trying to check RTK results against post-processed results of the same file, and they're not jiving very well vertically. The mountpoint that I'm using (CRTN's UCD1) has a CRTN NAD83 ellipsoid height value of -0.015 m as the geodetic monument (which is 0.0083 m below the ARP), but the ellipsoid height shown in J-Field is -0.515 m.

 

[Jim Frame]

I looked at the RTCM messages coming from the mountpoint (using SNIP), and when I converted the displayed XYZ to LLH (using NCAT) I get the position shown in the CRTN documentation (within 1 mm). The LLH position shown in J-Field is significantly different, even though the project reference system is CRTN NAD83. That doesn't seem right.

 

[giulio]

perhaps it is for this reason that Rtpk differs from the Rtk solution by a value of approximately 5/6 cm, equal to the value of the offset of the rtn station antenna