The GPS Toolkit: Open Source Clock Tools

Abstract : The GPS Toolkit (GPSTk) is an open source software project sponsored by the Space and Geophysics Laboratory of Applied Research Laboratories, The University of Texas at Austin. The GPSTk provides processing and analysis tools for GPS data. Clock Tools, a recent addition to the GPSTk, allows for basic clock stability analyses. These Clock Tools are interoperable with other GPSTk programs, allowing clock analyses to be easily run alongside other GPS analyses. The Clock Tools suite currently computes the Allan, overlapping Allan, modified Allan, total Allan, overlapping Hadamard, and dynamic Allan deviation stability metrics. These Clock Tools may be run from the command line with their output piped to other GPSTk programs. Data formatting and outlier removal routines for GPS and time interval analyzer datasets facilitate compatibility with the Clock Tools stability programs. Python and Octave graphing scripts were created to plot the raw data output by Clock Tools and current work is focused on a Qt-based graphical front-end for the suite. The graphical front-end will enable integrated stability metric selection and graphing. In the near term, we plan to expand the functionality of the graphical front-end and add noise-type identification functions. Results from the validation of Clock Tools are presented along with demonstrations of typical applications. Specifically, Clock Tools stability plots will be compared to those generated by Stable32. Analyses of RINEX datasets will be traced through the GPSTk toolchain, from calculation of observed range deviation to outlier removal, data parsing, stability calculation, and plot generation. A preview of the graphical front-end and its use will be presented. The analyses will be in the context of a worldwide GPS monitor station network with high-quality atomic frequency standards.