GPS Data Processing Using GAMIT/GLOBK and TRACK

9-13 January 2012
 Montserrat Volcano Observatory, Montserrat, West Indies.
This workshop will include both static and kinematic processing of GPS data with an emphasis on regional tectonics and volcano monitoring. It will include lectures and one-on-one tutoring of both continuous and survey-mode measurements; defining, global, regional, and local reference frames; temporal and spatial filtering of time series; modeling tropospheric, antenna, and loading effects in height estimates; combining solutions to estimate post-seismic and long-term crustal deformation; handling step-displacements due to earthquakes and instrument changes; developing an error model for velocity estimates, and high-rate GPS for seismic surface waves. Participants will be expected to have exercised the software on their own before the workshop and should bring laptops with the software installed or with remote access to their own labs.

Instructor: Tom Herring, MIT








Course logistics Introduction to GPS




GAMIT Standard Processing




GLOBK Overview




Tutorial session








Modeling details




Reference Frame Realization




Statistics of time series




Tutorial session using tsview, tsfit and tscon








Introduction to Track commands




Methods of tuning track




TrackRT installation and set up












Utility programs and scripts




Globk Prototyping tools




GPS Meteorological application




Tutorial session








Review of issues and questions (prepared based on comments)




Discussion and tutorial




Tutorial session




Wrap-up session



Notes and data sets

Mon    8:30-10:00        Course logistics Introduction to GPS                                 L01

In this lecture we go through the basic layout of the short course. We also introduce some of the basic concepts in GPS data processing, which we will revisit in later lectures. We look at the basic GPS observables and examine those contributions that are most uncertain in processing data. The main conclusions from this lecture are that high precision GPS requires external information in addition to just the GPS data and orbit information. In the current processing methods, all of the external information needed by GAMIT is automatically obtained but an Internet connection is required for access to information in international data archives.

Montserrat_Lec01_Intro.pptx                     Montserrat_Lec01_Intro.pdf


           10:30-noon       GAMIT Standard Processing                                              L02

In this lecture we look at daily processing using GAMIT. Nearly always the shell script sh_gamit is used for this processing. We will look at the directory structures that are normally used and the main functions and programs that are used in daily processing. We then look at the files that are important, and need user input, that are used in the processing. These files include station information, coordinates and velocities for stations, and other files that need to be kept up to date. We also look at the summary files that are generated and examine how to interpret these files. We also look at residual plots, which can be illustrative of problems in data processing. Finally we look at problems that can happen during processing and add some suggestions on how to solve these problems.

Montserrat_Lec02_gamit.pptx                   Montserrat_Lec02_gamit.pdf


           13:30-15.00      GLOBK Overview       L03

in this section we review the main features of globk and glred. It is important to note that glred is a simple program that allows multiple runs of globk and is used typically for time series generation. The topics we cover are the basic flow from daily gamit processing results (hfiles) to the results generated with globk.  We briefly review Kalman filtering and we look at the globk files and the estimation rules used. The program glorg which can be either run by itself or from within globk, is used to define the origin and orientation of the reference frame for the globk results.  We examine the output options and briefly look at the sh_glred script, which is a convenient way of invoking globk and its ancillary programs.

Montserrat_Lec03_globk.pptx                    Montserrat_Lec03_globk.pdf


           15.30-17:00      Tutorial session         

In this 1st tutorial we will do standard gamit processing using data in southern California. The stations used here are only a small set of those that are available through the Unavco archive. On day 166 of 2010 an aftershock of the El Mayor Cucapah earthquake that occurred in April of 2010, occurs. On this day we will use the sessinfo option in sh_gamit to break the day before and after the quake. Included in the same data set are hfiles from many more days of data that we will use in the globk tutorial.

Montserrat_Tut01_basic.pptx                    Montserrat_Tut01_basic.pdf

BajaTutorial.tar.gz (210 Mbytes)


Tues    8:30-10:00        Modeling details                                                                L04

In this lecture we look in more details at some aspects of modeling data in GPS processing.  We will look at effects that can be considered signal and sometimes noise in GPS processing. The basic areas we discussed our atmospheric delay modeling and signal scattering, and loading affects from the ocean, atmosphere and water.

Montserrat_Lec04_models.pptx                Montserrat_Lec04_models.pdf


           10:30-noon       Reference Frame Realization                                            L05

In this lecture we introduce the concepts of reference frame realization and the methods used in globk a to generate results in a specific reference frame. As we saw in earlier lectures, sites are affected by loading, mostly in the vertical direction, and these effects influence the reference frame realization. We look at ways of handling this in globk. We also examine local reference frame realizations and the way that earthquakes need to be treated in large analyses.

Montserrat_Lec05_RefFrame.pptx            Montserrat_Lec05_RefFrame.pdf


           13:30-15.00      Statistics of time series                                                     L06

We review the sources of noise in GPS position determinations and we look at some of the methods used to characterize noise. We look at the “realistic sigma” algorithm that is implemented in globk and tsview.  We also look at some methods that can be used to judge the quality of the uncertainty estimates derived by different techniques. Finally we look at the tools that are available in gamit/globk for error analysis and assessment.

Montserrat_Lec06_ErrorMod.pptx             Montserrat_Lec06_ErrorMod.pdf


           15.30-17:00      Tutorial session using tsview, tsfit and tscon

This tutorial session will be used to look at results from user data sets and also from the data set analyzed yesterday. Included in that data set at timeseries files that can be used to look at the statistics for the Salton Sea data.           


Wed    8:30-10:00        Introduction to Track commands                                      L07

This lecture looks at the basic methods used by the kinematic processing program track. We look at the equations that are used for the wide lane statistics and how these are used for ambiguity resolution. We look at the basic inputs for the program and how to run it. We then look at the statistics that should be checked and the basic commands that often need modification from the default values. We'll look at these more in the next lecture. We then look at some examples of track results. The tutorial session will include some of the data shown here.

Montserrat_Lec07_track.pptx                     Montserrat_Lec07_track.pdf



           10:30-noon       Methods of tuning track                                                    L08

In this lecture we look at the file outputs from track and how to interpret them. We then look at some of the track commands in more detail. We conclude by noting those options in track that often need to be modified from the default values. Our recommendation is to use the defaults initially and then tune based on those solutions.

Montserrat_Lec08_tracktuning.pptx         Montserrat_Lec08_tracktuning.pdf


           13:30-15.00      TrackRT installation and set up                                         L09

In this lecture we look at the use and installation of the real-time version of track called trackRT.  The real-time system uses the BKG program BNC to cast the GPS data to a real-time port that can be read by trackRT. The installation of the program is complicated by its use of the Nokia QT system and that the makefile needs to be modified to show the location this system. Installation on Linux operating systems is relatively straightforward. There are two versions of the program depending on which version of BNC is used. TrackRT is used for versions 2.5 and greater. Track RTB (binary) is used for earlier versions of BNC. We also discuss the trackRTr program that uses RINEX datafiles.

Montserrat_Lec09_trackRT.pptx                 Montserrat_Lec09_trackRT.pdf


           15.30-17:00      Tutorial

There are two tutorial folders in the trackTutorial folder. The BajaEQ folder contains high rate (5 Hz) GPS data collected at the time of an earthquake, and the kineMIT folder contains kinematic data collected at MIT. These later data can be processed in short baseline mode or in long baseline mode using one of its data from Algonquin Park in Canada (ALGO).

Montserrat_Tut03_track.pptx                     Montserrat_Tut03_track.pdf

trackTutorial.tar.gz (157 Mbytes)



Thur    8:30-10:00        Utility programs and scripts                                              L10

This lecture covers utility programs and scripts. These are organized into preprocessing and organization scripts, scripts that are used inside sh_gamit but are also useful standalone, and scripts that are useful for evaluating results. We also briefly review UNIX shell programs that are used extensively and are good to be familiar with.

Montserrat_Lec10_utilities.pptx               Montserrat_Lec10_utilities.pdf


           10:30-noon       Globk Prototyping tools                                                     L11

In this lecture we look at tools that can be used to test large globk solutions.  These tools allow timeseries to be analyzed for discontinuities from equipment changes and earthquakes and allow earthquake files to be developed that can be used in globk. These programs can also be used to realign reference frames very rapidly and to fit parameters for periodic signals and earthquakes. The a priori coordinate files generated here can contain the extended entries (periodic signals, earthquake the seismic signals) that can be used in globk. For large data sets these prototyping tools allow efficient testing of a globk run that might take one or two days to execute.

Montserrat_Lec11_Protoptype.pptx          Montserrat_Lec11_Protoptype.pdf


           13:30-15.00      GPS Meteorological application                                        L12

This lecture reviews some of the meteorological applications of GPS and we will discuss some of the utilities that can be used in gamit for meteorological applications.

Montserrat_Lec12_MetApps.pptx              Montserrat_Lec12_MetApps.pdf


           15.30-17:00      Tutorial session

There is no specific tutorial for this day. We will work on the data sets from previous days depending on the interests of the group. It is expected that different students will work on different projects and during this session we will have discussions informally. If an interesting issue is encountered then we may take time to present those results to the whole group.              



Fri       8:30-10:00        Review of issues and questions (prepared based on comments)

The contents of this lecture will depend on questions and issues the raised during the first 4 days the course.   Each student is expected to submit at least one question or suggestion of the material to be covered in this class.

           10:30-noon       Discussion and tutorial                                                     

This session will also follow on from the morning session addressing issues that have been encountered either in the tutorial data sets or

           13:30-15.00      Tutorial session

Tutorial session will follow from studies done earlier in the course.

           15.30-17:00      Wrap-up session       




In the photo, from left to right:

Ijaz Remsahai (Geography department, UWI, trinidad), Tappy Syers (MVO), Henry Odbert (MVO/UWI), Jean-Marie Saurel (OSVM Martinique/ IPGP), Anesh Gopee (Geography department, UWI, trinidad), Rob Watts (Seismic Research Centre, UWI, trinidad), Tom Herring (MIT), Stephanie Grizzle (UWI, Jamaica), Pat Joesph(Seismic Research Centre, UWI, trinidad), Machel Higgins (Seismic Research Centre, UWI, trinidad), Natalie Cotte (IPGP, Grenoble), Jean Bernard Dechabal (OSVG Guadeloupe/ IPGP), Sebastien Deroussi (OSVG Guadeloupe/ IPGP), Richie Robertson (Seismic Research Centre, UWI, trinidad)