We wish to incorporate our old Trimble
Pro XR with the GPS/Beacon MB type antenna along with our Locus receivers but can not find the specification for the antenna height ( from the base to the phase center). Will also need this info for the XL dome antenna which is the EC type. The data converted to RINEX and back into the Ashtech format seems to work fine, but the exact measurements would be nice. Anyone know where to look?

Art,

I can tell you from the spec's of the Locus, and from a great deal of personal experimentation (with Locus) the vertical offset - ARP to L1 phase center (or at least the mechanical L1 antenna)- is 0.125 m. I have no idea on the others mentioned.


J.D.

I think you can measure the phase center by observing 2 points with Locus, then replacing one Locus with the Trimble for a session and checking the difference in elevation that you get. It may be a lot more complicated than that, but it would be worth a try. My only question is the Trimble Pro XR a geodetic receiver capable of providing the accuracies you require?

Art:

Here are the antenna phase center models for the Trimble antennas that you've mentioned:

COMPACT DOME - EC:

;Processor name : WAVE Alpha
;Calibration time : Tue May 13 18:35:06 1997
;Reference antenna : Dorne Margolin Model T
;Calibrated antenna : Compact Dome
;Model : Order=10 Degree=0 Polynomial

;Mean phase center (mm) North East Up
L1NominalOffset = -0.8 1.5 1.9

;Elevation range (deg) Start Stop Step
ElevationRange = 5 90 5

;Azimuth step size (deg)
AzimuthStep = 0

;Azimuth/elevation corrections (mm)

AZ=0

;L1
2.2 1.5 4.4 7.4 9.5 10.7 11.1 11.2 10.9 10.3
9.5 8.3 6.9 5.3 3.6 2.1 0.9 0.0

TRIMBLE PROXR W/BEACON - MB:

;Processor name : WAVE Alpha
;Calibration time : Tue May 13 18:21:43 1997
;Reference antenna : Dorne Margolin Model T
;Calibrated antenna : Integrated GPS/Beacon
;Model : Order=10 Degree=0 Polynomial

;Mean phase center (mm) North East Up
L1NominalOffset = -0.9 0.7 9.7

;Elevation range (deg) Start Stop Step
ElevationRange = 5 90 5

;Azimuth step size (deg)
AzimuthStep = 0

;Azimuth/elevation corrections (mm)

AZ=0

;L1
2.6 2.8 4.3 6.2 8.0 9.5 10.4 10.8 10.7 10.1
9.1 7.9 6.5 5.1 3.6 2.3 1.1 0.0

I don't think that the Ashtech software allows the same level of phase center variation modelling as the other manufacturer's software does, so you are probably not going to do much more than use the Up offset to the L1 phase center.

Best regards,
Kent McMillan, RPLS Austin TX

Steve,

Good idea. The kinematic initialization bar can be used for this provided the antennae sizes will allow for them to both be placed on the bar. One thing though, I would probably use several different sessions. Simply measure a vertical offset from the measuring point to the bar on both antennae then observe and process. Compare measured offsets to ARP heights.

Shawn

Steve's method will give you a good vertical measurement to the phase center, but cannot determine the elevation and azimuth dependent variations required to properly model the antenna. For most survey work, it would be OK, though.

Does any one make software the can handle different antenna phase centers? I would like to find something that would let you select the antenna from a list similar to OPUS. AOS may have done this. I would also like to be able to process different manufacturers raw data files. I have found some non NGS, non Cooperative CORS sites in out area that only post data in there native format. It sure would be nice to be able to use that 1 second data from a receiver mounted on an order B point in my observations.

TGO appears to account for the azimuth/elevation characteristics of the various antennas, and has most of them available. My gripe is that I've been unable to add antennas to its list.

Translation of native data to RINEX can be accomplished by using UNAVCO's teqc, which is available without charge.


Modified By Jim Frame on 2/7/2002 at 1:12 PM

Steve,

As Jim mentioned, there are RINEX translators available at no cost from UNAVCO and the University of Berne that will convert nearly any proprietary format to RINEX. Ashtech Solutions can read the RINEX.

Regards,
Brian

Thanks for all the help! Sounds like the idea of using the kinematic bar would work. We can convert the Trimble to Rinex to use in Solutions no problem, but still need to know the antenna height. It is not needed in the Pathfinder carrier phase processing as it is built into the software same as Ashtech.