Question

I have ten L1 GPS receivers recording at the same time and place for about an hour (generally a little more). I use basic active antennae, nothing related to a precise GPS work. The expected relative precision is in the order of 10 cm. The distances between receivers range from 3m to 10m. For larger distances between sensors, the expected relative precision is even larger.

When using DDbase, only one station is kept fixed, generating 9 baselines all related to the fixed station. I compared the distances between calculated positions and the real distances measured with a meter (up to 10 m, I assume a few cm precision). For most of the stations the relative positioning is quite satisfactory (less than 10 cm difference). But in all cases there are at least 2-3 distances above 40 cm error. The quality of the positioning varies a lot with the selected fixed station. I tried almost all options described in man page but no effective improvement was found.

I have two questions:

  • does it matter if the absolute positioning of the reference station (fixed one) is approximately known (1 to 5 m error)?
  • does it improve the positioning if all possible baselines are included (not only the baselines from the fixed station but the 45 couples involved in this network)?

-- MarcWathelet - 09 Oct 2009

Answer

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Hi, I try to solve baseline with DDBase and Trimble Geomatic Office. I have received something wrong. My setting file's --Log LogDDBase.log --ObsPath D:\Data\IGSVN\2009\081 --NavPath D:\Data\VN\Nat --EOPPath D:\Data\VN\Nat

--ObsFile bako0810.09O,BAKO --PosXYZ -1836969.1955,6065617.0371,-716257.8366,BAKO --TropModel ModHopH,BAKO

--ObsFile cusv0810.09O,CUSV --PosXYZ -1132913.7678,6092530.5657,1504633.5192,CUSV --TropModel ModHopH,CUSV

--ObsFile kunm0810.09O,KUNM --PosXYZ -1281255.629,5640744.789,2682879.057,KUNM --TropModel ModHopH,KUNM

--ObsFile ntus0810.09O,NTUS --PosXYZ -1508022.7800,6195576.6820,148799.4690,NTUS --TropModel ModHopH,NTUS

--ObsFile pimo0810.09O,PIMO --PosXYZ -3186293.8000,5286624.2800,1601158.3100,PIMO --TropModel ModHopH,PIMO

--NavFile igs15236.sp3 --NavFile igs15240.sp3 --NavFile igs15241.sp3 --NavFile igs15242.sp3

--EOPFile EOPP9079.TXT --EOPFile EOPP9083.TXT --EOPFile EOPP9086.TXT

--Fix KUNM --Converge 1.00e-10 --Freq L3 --nIter 50 --RZDtimeconst 2.0 --RZDnIntervals 12 --RZDsigma 0.1 --MinElev 20.0 --DT 15.0 --PRSconverge 1.00e-10 --PRSMinElev 20.00

--BaseOut CUSV-KUNM --BaseOut CUSV-PIMO --BaseOut CUSV-NTUS --BaseOut CUSV-BAKO

DDBase gave baseline that (DX, DY, DZ, Baseline) Final Baseline CUSV-KUNM 148338.400785 451783.745262 -1178247.759453 1270582.786081 Final Baseline CUSV-PIMO 2053377.071172 805904.975364 -96526.585559 2207975.907353 Final Baseline CUSV-NTUS 375105.050971 -103046.852237 1355832.581656 1410533.389360 Final Baseline CUSV-BAKO 704051.967285 26911.497162 2220889.134147 2329970.374810

I tried to use Trimble Geomatics Office and it gave that (DX, DY, DZ, Baseline) CUSV KUNM -148341.110m -451782.571m 1178246.543m 1270581.557m CUSV PIMO -2053378.977m -805904.329m 96525.032m 2207977.376m

Diffirence ~ 3m... This 's error in file setting?

-- NguyenVanNguyen - 06 Jun 2010 No such template def TMPL:DEF{PROMPT:supportquery}

Topic revision: r2 - 06 Jun 2010, NguyenVanNguyen
 

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