The ARP to Phase Center height is 48.02 mm, but there’s no north marker on the antenna (that I see). The doc says “… A multi-feed design scheme is used to ensure the coincidence of phase center and geometric center, and minimizes the influence of the antenna on measurements.” So … does that mean there is no XY offset for the phase center?
It’s the connector, as shown on the NGS file
North Reference Point (NRP) is labeled as RXC (Receiver Connector).
Phase Center Offsets for SFESPK6618H
| Frequency | North Offset (mm) | East Offset (mm) | Up Offset (mm) |
|---|---|---|---|
| L1 (GPS) | +0.48 | +0.13 | 48.02 |
| L2 (GPS) | -0.19 | +0.43 | 35.91 |
| L5 (GPS) | -1.13 | -0.15 | 31.35 |
[Edit: chart has errors, see below]
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Hey Ryan, thanks!
I’m an admitted GNSS antenna novice. I’m guessing many others are out there as well. Maybe this is a good spot to capture some learning info?
Can you give full URLs for where those docs come from? Also, perhaps some pointers as to learning how to interpret some of the table I’ve seen?
Thanks!
Sure.
Here’s all of the SparkFun Antennas that have NGS Calibrations:
https://geodesy.noaa.gov/ANTCAL/index.xhtml?manu=SparkFun%20Electronics#
If you hover over DRAWING, you will see the graphic I posted:
To view the calibration results, you can click the ANTEX link.
https://geodesy.noaa.gov/ANTCAL/LoadFile?file=SFESPK6618H_NONE.atx
Scroll down until you see this line:
G = GPS constellation, 01 = L1 Band
As you will notice, I messed up the chart in my previous post 
Keep scrolling to G02 , for GPS L2 Band which says:
And G05, which is GPS L5 band:
So the corrected chart would be:
| GPS freq | ANTEX freq code | North (mm) | East (mm) | Up (mm) |
|---|---|---|---|---|
| L1 | G01 | 0.47 | -1.26 | 48.02 |
| L2 | G02 | 2.73 | -1.87 | 35.91 |
| L5 | G05 | 3.16 | -2.02 | 36.91 |
This antenna has a fairly large delta between the L1 and L1 Phase Centers (UP). If you are interested in how much “Z” to add to your Rod Height for a Rover, it’s probably safest go add 48mm (L1 phase center) to the ARP.
If you are using OPUS or CSRS-PPP, just make sure to select the correct antenna and all the processing is done for you with the .atx file, for each specific signal.
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