Reprocessing the complete history of VLBI observations with VieVS

VieVS User Workshop7 – 9 September, 2010

Vienna

Reprocessing the complete history of VLBI observations with VieVS

Sigrid Böhm

VieVS User Workshop 2010 2

Why should one do that?There are new solution methods/strategies.There is a new software.You would like to create a database with the optimal parameterization for each session.You are interested in time series of special parameters (such as ERP) covering the longest time span available.


TS of special parameters - EOPWhich sessions to choose for processing?

Define exclusion/suitability criteriahttp://vlbi.geod.uni-bonn.de/IVS-AC/data/exclude.txt

No local or regional networksNo sessions with < 3 stations (except for dUT1 determination from Intensives)No sessions with < 250 observations

Create a process listBasic list to start: e.g. use mk_list to get a list of intensive sessions, add this int_list to exclude.txt and then use mk_list with the option ‘ALL’ except ‘exclude.txt’.

Use preliminary list and process all sessions with a basic parameterization

Then you can use the data in LEVEL3 to make an extended exclude list according to the previously defined criteria and find sessions which are not working properly


Interesting parameters for the criteria and for “not working properly“

DATA/LEVEL3/SUBDIR/opt_sessname.mat:opt_.total_obs = number of observationslength(opt_.stat) = number of stationsopt_.mo = error of unit weight a posterioriopt_.cond = condition number of N-matrix (a bit difficult to judge)

In Matlab: you can use diary(‘thisrun.log’) to store the output from the command window, diary off to stop the function


e.g. log-file: search for “RCOND”



check “geometry“Take the information from the files stored in DATA/LEVEL1 and plot the network

Regional network

→ exclude the session

Other log-file “messages“Problems with tidal ocean loading at station VLBA85 3 Problems with tidal atmosphere loading at station VLBA85 3 Problems with non-tidal atmosphere loading at station VLBA85 3 Problems with thermal correction at station VLBA85 3 Problems with VMF1 at station VLBA85 3


For the remaining sessions with high 0

There is no other way than … going through all of them individuallyfinding clock breaks, bad stations etc.creating hundreds of OPT files

Most welcome alternative … write a module for the automatic detection of clock breaks and creation of OPT files


Update process listAdd all sessions you have sorted out to the „exclude“-file and run mk_list againCreate an outlier file for each session with some simple parameterization

Decide about your final parameterization according to your needs


Some rules for EOP estimationBasic approach for daily resolution:

Estimate all five EOP xp,yp,dUT1,dX,dY with 1440 min intervalEstimate station coordinates and apply NNR, NNT conditions

Polar motion with subdaily resolution:Do not estimate but fix nutation!!Fix station coordinates


R1 and R4 networks



Comment on correlation coefficients

The Matlab function corrcoef works correctly but not for our purpose.

It does not take a covariance matrix as input! (Refer to Matlab Help for further info)

Correlation coefficient:

yyxx

xyxyr

Qxx = inv(atpa_.mat);varii = diag(Qxx);Rxy = Qxx./sqrt(varii*varii');

5 EOP 24 hours, NNR/NNT


3 ERP 1h, nut 24 h, NNR/NNT


3 ERP 1h, nut fix, NNR/NNT


3 ERP 1h, nut fix, coord fix


Reprocessing the complete history of VLBI observations with VieVS

Documents

Transcript of Reprocessing the complete history of VLBI observations with VieVS