Hello,
I am trying to configure antennas to bring RINEX data in GNSS solutions for the 4600LS and 5800.
Would someone explain to me how does the nominal offset value relate to the phase center value?
For example, on the 5800:
- The offset from the bottom of antenna to the phase center is 64.9mm.
- The L1 nominal offset is 31.9mm.
- The L2 nominal offset is 18.7mm.
What would be the expression to calculate the required C1 and C2?
Here's that data for one of the two antennas that I am using.
Thanks folks,
Georges
;Processor name : MRGPCT 1.0
;Merge time : Wed Aug 07 01:45:00 2002
;Calibrated antenna : 5800 Internal
;Mean phase center (mm) North East Up
L1NominalOffset = -0.4 0.4 31.9
L2NominalOffset = 0.9 0.4 18.7
;Elevation range (deg) Start Stop Step
ElevationRange = 5 90 5
;Azimuth step size (deg)
AzimuthStep = 0
;Azimuth/elevation corrections (mm)
AZ=0
;L1
-9.9 -5.5 -1.8 1.1 3.6 5.4 6.8 7.5 7.6 7.3
6.6 5.6 4.5 3.4 2.3 1.4 0.6 0.0
;L2
-7.7 -2.9 -0.6 0.7 1.7 2.5 3.2 3.8 4.2 4.2
4.0 3.4 2.8 2.0 1.2 0.6 0.2 0.0
2.10 OBSERVATION DATA G (GPS) RINEX VERSION / TYPE
DAT2RINW 3.10 001 gc 29SEP11 21:26:16 PGM / RUN BY / DATE
gc gc OBSERVER / AGENCY
4534155914 TRIMBLE 5800 Nav 2.31 Sig 2.31 REC # / TYPE / VERS
TRM5800 ANT # / TYPE
----------------------------------------------------------- COMMENT
Offset from BOTTOM OF ANTENNA to PHASE CENTER is 64.9 mm COMMENT
----------------------------------------------------------- COMMENT
59142680 MARKER NAME
5914 MARKER NUMBER
-1220570.1024 -2695274.2781 5631568.6423 APPROX POSITION XYZ
2.0000 0.0000 0.0000 ANTENNA: DELTA H/E/N
*** Above antenna height is from mark to BOTTOM OF ANTENNA. COMMENT
----------------------------------------------------------- COMMENT
Note: The above offsets are CORRECTED. COMMENT
Raw Offsets: H= 2.0000 E= 0.0000 N= 0.0000 COMMENT
----------------------------------------------------------- COMMENT
Assuming you are using the older ngs relative values (which are the default values in GNSS Solutions for all the preconfigured antennas), you need to read this:
http://www.ngs.noaa.gov/ANTCAL/documents/format.txt
and use these values:
http://www.ngs.noaa.gov/ANTCAL/LoadFile?file=ant_info.003
The offsets you are looking for need to be converted from mm to m.
These antennas are both by default in my GNSS Solutions antenna list, so I am unsure why you are messing with them...
Thanks for the link. I did find the exact calibration antenna for the 5800 and created the antenna model. Couldn't find the one about the 4600, though.
With this antenna configuration, what I am finding (for unexplained reasons) is that instead of using the height of 2.000m (the GPS was on a 2.000m pole), by using the height of 1.870m, the processing and adjustment results are comparable in value to TBC.
This difference of 13 cm's represents 2 * the antenna phase center of 64.9mm.
Curious, isn't it?
One thing about RINEX files, I never played with those before. There's more to them than "plug and play", as I first believed.
Georges
Yeah, but the Rinex files are plain text. The entire file format is explained in detail online.
It's really hard to know from the information you are giving here what is going on. But, your statement that "13 cm's represents 2 * the antenna phase center of 64.9mm" could also be interpreted as "I am not sure if the offset should be positive 64.9mm or negative 64.9mm. But if I apply the offset incorrectly, this might also explain what I am seeing..."
Thanks, that seems to be something along that line.
Well, all I figured out so far is (by following the same export to RINEX procedure options), the 4600LS data comes without a hitch but something appears to be going on with the 5800.
