Tuning AUTCLN for editing

Autcln basics Controlled by the autcln.cmd file The defaults in the program are set for data from modern receivers These default values need not be included in the command file Post-fit cleaning is primary exception Can be "tuned" extensively Very useful for data from older receivers 13-Nov-18 GAMIT/GLOBK Tutorial 5

Basic aims and operation Generate a set of one-way phase time series in which all cycle slips are either corrected (with integer step functions) flagged (to introduce real-valued offset) “Bias flags” are used for cycle slips that cannot be resolved to integer values Generate one-way phase residuals that can be used for data weighting 13-Nov-18 GAMIT/GLOBK Tutorial 5

How autcln works (1) Generate models for receiver and satellite clocks Measure clock offset epoch-by-epoch using pseudorange data Align offsets with the polynomial estimated from the K- and J-files. (2) Identify and flag possible jumps in phase data using wide-lane (WL) when available and/or ionospheric-delay (LG) phase 13-Nov-18 GAMIT/GLOBK Tutorial 5

How autcln works (II) (3) Align the phase data with the range clock solution look for large slips in the phase data look for jumps in the ionospheric delay (4) Scan selectively double differenced phase Look for jumps Attribute each DD jump to 1 sat and 1 station (5) Iterate steps 1-4 to improve estimates Phase data set now bias flags at each possible slip and after gaps 13-Nov-18 GAMIT/GLOBK Tutorial 5

How autcln works (III) (6) Remove short segments (Actually, they are assigned a flag to “unweight” them.) (7) Estimate the number of cycles missing (jumped) at each bias flag by polynomial fits to surrounding data use good data from other stations and satellites. determine integer values and their reliability 13-Nov-18 GAMIT/GLOBK Tutorial 5

How autcln works (IV) (7) Iterate step 7 using previously-cleaned data (8) Estimate receiver and satellite clock offsets again use the phase data in an iterative process generate new one-way phase residuals (sum for each station and satellite is zero) (9) Write clean C-files preserve input C-files, OR over-write intermediate C-files 13-Nov-18 GAMIT/GLOBK Tutorial 5

autcln command file Go to your computer to examine the distributed autcln.cmd file Note the use of the POST option Which options would you change for older code-less data? Using sh_gamit makes 2 summaries: autcln.cmd.prefit AND autcln.cmd.posfit 13-Nov-18 GAMIT/GLOBK Tutorial 5

Checking autcln.sum files Postfit scatter Usually RMS < 10 mm Discarded data Usually < 10% data discarded More than 20% discarded indicates problem Missed cycle slips are now very rare Most problematic slip is 1 cycle in L1 AND 1 cycle in L2 does not change WL 13-Nov-18 GAMIT/GLOBK Tutorial 5

Why are ALL the data from my favorite station deleted? This question is number 1 FAQ Bias flags too close together Post-fit phase RMS too large Check editing reports in autcln.sum Bad apriori coordinates Example /dell3/tah/swis/gps00/1999_149/autcln.post.sum 13-Nov-18 GAMIT/GLOBK Tutorial 5

Autcln commands Read the $HELP_DIR/autcln.hlp file Also output by just typing autcln 13-Nov-18 GAMIT/GLOBK Tutorial 5

Tuning autcln dd_fit_tol ion_jump trim_oneway sets the sizes of jumps to be flagged as ratio to rms min size max size ion_jump similar parameters for ionspheric jumps trim_oneway sets minimum sizes for segments of data as time number of epochs ratio to good length min at end 13-Nov-18 GAMIT/GLOBK Tutorial 5

Summary Default autcln.cmd usually works fine Tuning is useful for anomalous data some old data If you need to tune delete the link in the day dir -> tables dir copy the autcln.cmd file to the day dir modify the autcln.cmd file in the day dir re-run sh_gamit (or bexpt?.bat) for that day 13-Nov-18 GAMIT/GLOBK Tutorial 5