Jim Frame
Well-Known Member
(I wasn't able to reply to Kelly's thread on this subject, so I started a new one.)
First, I want to say that I saw this coming. As soon as I saw the original 2A model designations, I thought, "Uh oh." Specifying the bottom of a removable adapter as the ARP not only broke from long-standing tradition, it also just about guaranteed confusion. While it would have been better never to have gone down this path, at least an effort is underway to rectify it.
But I'm not convinced that it's been rectified yet, at least as far as OPUS is concerned. The image that Kelly posted showing the "new" JAVTRIUMPH_2A NONE isn't the one that currently appears on the NGS antenna calibration page:
http://geodesy.noaa.gov/ANTCAL/LoadImage?name=JAVTRIUMPH_2A+NONE.gif
Also, I happen to have 6 multi-hour observations on a wide-open point that collectively call into question the model, or at least the way OPUS is handling it. 4 of them were made with my JAVTRIUMPH_2A NONE between December 26 and December 31, 1 of them with aTRM33429.00+GP NONE on January 26, and 1 with a TRM22020.00+GP NONE on January 27. All occupations used SECO 2-meter fixed-height tripods, and all were reprocessed through OPUS today.
The TR2 had the 25mm adapter installed, as that's the only way I have to get the unit on the tripod's 5/8"x11 mount:
Thus the ARP height I used for the TR2 OPUS submissions was 2.025 m. The 2 Trimble antennas go right on the tripod's mount, so I used a 2.000 m ARP height for their OPUS sessions.
The NAD83 ellipsoid heights returned by OPUS for the station using the TR2 ranged from -20.066 m to -20.087 m, for a spread of 0.021 m and a mean of -20.027 m. The Trimble 33429 session came in at -20.044 m, and the Trimble 22020 session at -20.027. The 2 Trimble antennas are very similar and well-characterized, so I consider the spread of 0.017 m and the mean of -20.036 m to be valid.
The difference between the TR2 mean and the Trimble mean is 0.040, which I regard as significant given the number and length of the observations.
If OPUS is not handling the TR2 ARP height correctly -- by using 84.3 mm as the ARP-to-phase-center, instead of 59.3 mm -- the the TR2 mean would come within 15 mm of the Trimble mean. That still seems a bit large to me, but much more reasonable than 4 cm.
First, I want to say that I saw this coming. As soon as I saw the original 2A model designations, I thought, "Uh oh." Specifying the bottom of a removable adapter as the ARP not only broke from long-standing tradition, it also just about guaranteed confusion. While it would have been better never to have gone down this path, at least an effort is underway to rectify it.
But I'm not convinced that it's been rectified yet, at least as far as OPUS is concerned. The image that Kelly posted showing the "new" JAVTRIUMPH_2A NONE isn't the one that currently appears on the NGS antenna calibration page:
http://geodesy.noaa.gov/ANTCAL/LoadImage?name=JAVTRIUMPH_2A+NONE.gif
Also, I happen to have 6 multi-hour observations on a wide-open point that collectively call into question the model, or at least the way OPUS is handling it. 4 of them were made with my JAVTRIUMPH_2A NONE between December 26 and December 31, 1 of them with aTRM33429.00+GP NONE on January 26, and 1 with a TRM22020.00+GP NONE on January 27. All occupations used SECO 2-meter fixed-height tripods, and all were reprocessed through OPUS today.
The TR2 had the 25mm adapter installed, as that's the only way I have to get the unit on the tripod's 5/8"x11 mount:
Thus the ARP height I used for the TR2 OPUS submissions was 2.025 m. The 2 Trimble antennas go right on the tripod's mount, so I used a 2.000 m ARP height for their OPUS sessions.
The NAD83 ellipsoid heights returned by OPUS for the station using the TR2 ranged from -20.066 m to -20.087 m, for a spread of 0.021 m and a mean of -20.027 m. The Trimble 33429 session came in at -20.044 m, and the Trimble 22020 session at -20.027. The 2 Trimble antennas are very similar and well-characterized, so I consider the spread of 0.017 m and the mean of -20.036 m to be valid.
The difference between the TR2 mean and the Trimble mean is 0.040, which I regard as significant given the number and length of the observations.
If OPUS is not handling the TR2 ARP height correctly -- by using 84.3 mm as the ARP-to-phase-center, instead of 59.3 mm -- the the TR2 mean would come within 15 mm of the Trimble mean. That still seems a bit large to me, but much more reasonable than 4 cm.