x_update(1gmt) [debian man page]
X_UPDATE(1gmt) Generic Mapping Tools X_UPDATE(1gmt) NAME
x_update - Archiving of Cross-Over Information SYNOPSIS
x_update cross-overfile [ -Xxbase ] [ -Llegbase ] [ -V ] [ -Wmax ] DESCRIPTION
x_update reads the ASCII file produced by x_over and writes the information to the database files xx_base.b and xx_legs.b (unless other filenames are specified on the command line) using a compact, binary format. The options recognized are: -X Indicate alternate xx_base.b file. -L Indicate alternate xx_legs.b file. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. Reports the pair currently being pro- cessed. -W Prints a warning if the number of COEs generated by any pair of legs exceed max. BEWARE
For security reasons the xx_legs.b are first renamed to xx_legs.b_old, to prevent loss of information if a black-out or system crash should occur during writing of the new xx_legs.b file. It is recommended that the old file is left on the disk in case of other disasters. Note that x_update does not check if a pair of legs already exist in the xx_base.b file. It is the user's responsibility to ensure that duplica- tion of information does not occur. Should some pairs already in the database need to be re-examined, then run x_remove which will wipe out all traces of the specified cruises from the x_system data base files. Now we can pass the pairs that need to be redone through x_over/x_update again. SEE ALSO
GMT(1), x_system(1) REFERENCES
Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers & Geosciences, 15, 333-346. GMT 4.5.7 15 Jul 2011 X_UPDATE(1gmt)
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X_SOLVE_DC_DRIFT(1gmt) Generic Mapping Tools X_SOLVE_DC_DRIFT(1gmt) NAME
x_solve_dc_drift - Find Best-fitting D.C.-shift and Drift Estimates SYNOPSIS
x_solve_dc_drift [ -Xxbase ] [ -Llbase ] [ -Iignorefile ] [ -S ] [ -Citeration ] [ -Mmin_nx ] [ -Rwest/east/south/north ] [ -Uuselegsfile ] [ -V ] [ -Bbinfile ] [ -AASCIIfile ] DESCRIPTION
x_solve_dc_drift will read the database files and, by iterating, find the best-fitting regression line to the <time,COE> points for each leg that minimizes the overall standard deviation of the data set in a least squares sense. Finally, correction file(s) are created. -X Indicate an alternate database to read. [Default is xx_base.b]. -L Indicate an alternate legbase to read. [Default is xx_legs.b]. -I Ignore information for certain legs (that might be bad, etc). -S Reset the old d.c.-shift and drift estimates to zero before iterating. -C Specify how many iterations to do. Default is interactive session. -M Solve for drift only if the leg has more than min_nx cross-overs. -R Only take COEs inside this region into account. [Default is world]. -U Solve for corrections involving COEs from legs in the uselegsfile only. -B Create a binary correction file (which can be read by x_list and gmtlist). -A Create an ASCII correction table. At least one of -A and -B must be specified. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. BEWARE
The reason for the -M option is that if the COEs are few, then a stable estimate of the slope may not be obtained (e.g. when most of the COEs occur midway between ports). However, in most cases the bulk of the COEs do occur near the ports so that a drift estimate can be com- puted. Conventional wisdom recommends plotting the time-series and the computed regression line to see if it makes sense. SEE ALSO
GMT(1), x_system(1) REFERENCES
Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers & Geosciences, 15, 333-346. GMT 4.5.7 15 Jul 2011 X_SOLVE_DC_DRIFT(1gmt)