Hi there, does anyone know what the receive antenna height offset is for the GPS-23847 antenna? The specs don’t mention it. Many thanks.
I don’t have one at the ready for you. Let me check.
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Welcome @PLAN8 !
The APC normally isn’t provided or published for these types of tiny Helical antennas.
AFAIK, NGS doesn’t perform Antenna Calibration on any Helicals, as they aren’t normally used for control work.
You can compare a specific Helical to a calibrated geodetic antenna on a test rig for an empirical offset. I’ve found them to be repeatable individually, but you need to establish a North Reference point and check each one.
In my mind, we trade a published & qualified APC for the extreme portability of these tiny helical antennas. I believe they are useful in their intended application, but it’s not something I grab when targeting “cm” absolute accuracy for a position (without a lot of extra care on the front-end).
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That’s great, thanks for the breakdown and advice! Cheers!
Great! Thanks!
As @rftop points out, take these offsets with a grain of salt since they can’t be easily verified. In short, 37.5mm is the APC. We’ll update our docs accordingly.
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That’s amazing! Thank you!
Hello friends.
I have this antenna in a Postcard with the portability shield.
I also have professional equipment, and I used it to compare the heights.
Experimentally, at a known point, the APC hit me 2 cm from the base of the antenna. I repeated this many times, and it always hit me around 2 cm.
It’s just above the thick part of the antenna.
Regards
Angel
Of course, the tests were conducted within an hour. If you test it 12 hours later, for example, it may produce slightly different results. Try it and share.