Crossover Error Analysis Packages

When several data sets collected along tracks (such as marine underway data by research vessels, land traverses, or remotely sensed data by satellites) are merged, one usually finds that the observed values at locations where tracks intersect do not agree. Systematic errors such as drifts, offsets, or differing scale factors can be detected by analyzing the crossover errors (COE). Applying the resulting COE corrections to the track data can dramatically improve overall data quality and is essential prior to gridding track data. The XSYSTEM is a set of 9 command-line programs that collectively addresses the task of undertaking a complete crossover analysis for track data.

XSYSTEM is developed and maintained by Paul Wessel. X2SYS, a successor to XSYSTEM, is currently being distributed with GMT as well and will eventually replace XSYSTEM. X2SYS is much more flexible when it comes to what kinds of data files it can read, whereas XSYSTEM currently is hardwired to a particular format (the .gmt files of GMT's old MGG supplement).

References to use of XSYSTEM

  1. Wessel, P. 1989, XOVER: A Cross-over Error Detector for Track Data, Computers & Geosciences, 15, 333-346 [PDF].

  2. Wessel, P. and A. B. Watts, 1988, On the Accuracy of Marine Gravity Measurements, J. Geophys. Res., 93, 393-413 [Table A1].

References to use of X2SYS

  1. Wessel, P., 2010, Tools for analyzing intersecting tracks: the x2sys package, Computers & Geosciences, 36, 348-354 [PDF].

Availability of XSYSTEM and X2SYS source code

XSYSTEM and X2SYS are both distributed with GMT as supplemental packages. See the GMT home page for download details.

Last update January 6, 2013 by Paul Wessel