Does anyone know if the TRM 59800 antenna has a reference to align in North. I wouldn't normally worry about antenna alignment for static this but it is for university research and want to minimise potential errors.
Wouldn't the machined tick be aligned to the North?
M
> Wouldn't the machined tick be aligned to the North?
That's certainly a reasonable interpretation, though I haven't found anything in the antenna calibration data to positively identify the tick slot as the north point. Then there's this note from UNAVCO:
> The antennas will either be labeled with a (true) north arrow, or in the case of choke ring antennas orient the cable connector to true north.
Unfortunately, the connector is opposite the tick slot; fortunately, if you guess wrong you'll only be looking at an error of about 2 mm, as the L1 phase center east eccentricity of this antenna is only 1 mm (the north eccentricity is 0 mm), and the elevation-dependent response is symmetrical about the vertical axis.
My understanding is that, where it is considered at all, it is not important which part of the antenna points north as long as its the same part with each occupation.
Agreed, actually it doesn't even need to be north, as long as you are using the same procedure on ALL of your antennas it could be any direction, north is just the standard, BECAUSE if mixing in any CORS they are all allegedly pointing to north... Absent an index mark, I believe as mentioned the standard is for the antenna connector to point north, of course if you have an index mark that isn't aligned with the antenna connector you have a conflict.
I don't know that it is as critical these days, BUT old habits die hard, so I always point my antenna connectors north for any static work...
SHG
It's my understanding (especially from early days of GPS) that specific antenna corrections were determined and given in relation to North. So, if you wanted to apply corrections for that antenna you needed to have it aligned North. And I have seen some antennas that actually had a North arrow on them.
Most modern antennas are "centered" and whatever error there is is below the accuracy levels of GPS.
> Agreed, actually it doesn't even need to be north, as long as you are using the same procedure on ALL of your antennas it could be any direction, north is just the standard
This is only true if:
a) you are doing differential positioning
b) you have the same antenna for the base and rover.
For point positioning,or with mixed antenna types you need to get it right, of course keeping in mind the level of accuracy you actually need.
Thanks for posting the definitive answer!