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UNAVCO 1996 Annual Report
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2.1 Data Processing and Analysis Support

A proposal entitled Collaborative Proposal: Support for Fundamental GPS Research - UNAVCO Facilities for Data Processing was submitted to the NSF EAR-IF Program by UCAR on December 30, 1996 with preliminary notice of award on May 23, 1997. A thirty month grant totaling $105,390 was issued to Bob King at MIT for user support and software development for the GAMIT and GLOBK GPS data processing software and a thirty month $150,000 grant was issued to Chris Rocken's GPS Research Group at UCAR for user support for Bernese processing software. The UCAR work includes a subcontract to the University of Texas at Austin for development and support of GLOBK post-processing tools. Planned activities under each of these grants are discussed briefly below.

MIT Support for GPS Data Processing and Analysis

The MIT group under Bob King was funded for three activities supporting GPS investigators using the GAMIT and GLOBK software including training for investigators and their overseas collaborators, improving the reliability and user interface to the software, and improving documentation. Since March, MIT has hosted 12 visitors involved in data processing for NSF-supported investigations. Most of the expenses for this training were supported by the associated research grants, foreign institutions or, in the case of a two-week workshop of Eastern Mediterranean collaborators, by an NSF International Programs grant (INT-9724114). The UNAVCO grant supported salary and computer expenses associated with software enhancements, trouble shooting, and documentation stimulated by the visitor training while adding value for all UNAVCO Community investigators using GAMIT and GLOBK software. In addition to the training sessions, the MIT group responds to about ten e-mail questions per week regarding the use of the software.

In September of 1997 the MIT group released new versions of both GAMIT and GLOBK, incorporating changes to over 240 subroutines since the last release in February. Many of these changes fixed bugs or provided better feedback to users for anomalous data files or incorrect setup of control parameters. Others added new features, including more efficient pre-processing, tighter data editing through the use of post-fit residuals, correct use of Leica brand receivers and antennas, radiation-pressure and transmitting antenna models for Block IIR satellites, new parameters to model atmospheric gradients, and a better means of defining the reference frame at the last step in processing.

During FY98, three modifications will be made to the software to improve its accuracy for specific applications. "Stitching" together the orbital parameter estimates from daily processing at Scripps will give the ability to use the stability of long orbital arcs to improve station-position estimates from measurements acquired prior to the 1994-1996 expansion of the global tracking network. The addition of ocean tides to the model of station motions will improve accuracy for a number of important near-coastal regions. Finally, expansion of the atmospheric gradient model to allow for temporal changes will improve the utility of GAMIT for meteorological studies.

The GAMIT and GLOBK documentation has been updated to incorporate the new features, and a new section of the GLOBK manual was written to provide analysts with rationale for new approaches to reference-frame definition and more current examples for regional and global networks. Software and documentation can now be downloaded by ftp or via a new Web page (http://bowie.mit.edu). A priority for the next few months will be to expand the information available on the Web page to include answers to frequently asked questions. By the end of 1997, all GAMIT and GLOBK documentation is planned to be on-line, including a short tutorial to introduce the software and a capability to allow users to search for new features using keywords. MIT will continue to conduct individual training and provide user support for GAMIT and GLOBK through FY98.

UCAR Support for Data Processing and Analysis

Chris Rocken's GPS Research Group at UCAR has been funded as of September through the collaborative proposal with MIT to support GPS researchers using the Bernese high-precision GPS software for data analysis. In FY98, the Research Group will provide training to visiting scientists who will bring their own data sets for analysis at Boulder, assist in the analysis of problem data sets via telephone and remote login, and maintain a Web site for frequently asked questions related to the use of Bernese. The group will also develop and support graphic tools that aid data analysis and will collaborate with MIT and the University of Texas at Austin on the development of GLOBK post-processing tools for broad community use.


1997 Annual Report - 27 OCT 1997

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