The GSAC Newsletter  			                                       Number 1, 17 July 2013


Contents:

    About the GSAC Newsletter 
    What is GSAC
    GSAC Status
    Improving GSAC Installation : the GSAC Prototype Database
    GSAC Workshop


About the GSAC Newsletter 

    This GSAC Newsletter has recent news about GSAC, for persons interested in GSAC installation and services.  This is the first number.  A newsletter appears to be a useful way to share information about GSAC developments, in place of multiple similar emails to many GSAC users.   I  plan to send out additional GSAC newsletters by email at irregular intervals depending on the need, perhaps one newsletter every month.  

    If you do not wish to receive future GSAC newsletters, please send me word.


What is GSAC

    GSAC, officially "GSAC-WS" or "GSAC Web Services," is a free, open-source software package for geodesy data repositories, providing web services for information about stations, instruments, and their data files. GSAC provides a complete set of the latest web services for search, discovery, and download of geodesy data in existing repositories.  Any organization with geodesy data files, and with a database of information about the data files and related stations and instruments, can implement data repository web services by utilizing GSAC. GSAC uses the latest software technology for the latest web services. 

    GSAC search results for station information can be in any of several formats including web pages, SINEX, GAMIT station.info files, SOPAC XML site logs, and several other forms.  GSAC also provides geodesy data file downloads from your server.   Note that GSAC is designed to easily permit multiple GSAC repositories to be accessed by one query, enabling collaborative repositories, without any extra software at any single GSAC installation.

    The UNAVCO GSAC website is at http://facility.unavco.org/data/gsacws/gsacws.html.  The web site has general information, links to operating GSAC repositories, installation support, and a User Guide for scientists using GSAC services.

    GSAC is in operational use at three locations in the U.S. and has been installed at one location in Europe (not online there yet).



GSAC Status

     GSAC activities are at a high point, with two more requests in the past week to UNAVCO from new agencies interested in installing GSAC.   Presently there are five projects planning to install GSAC soon:

        University of Beira Interior, Covilhã, Portugal
         
        Vedur Iceland

        National Observatory of Athens

        RENAG, France

        EPN CB, Belgium 

        Several new installations will surely reveal things to add or improve in GSAC, for installation as well as operations.   If you are working with GSAC, do not hesitate to email questions and suggestions.


Improving GSAC Installation : the GSAC Prototype Database

    GSAC relies on a database to provide the information it requires about your GNSS stations and instruments, and also about GNSS data files if you have file download service.  If you already have a database with adequate information GSAC can use that.   I am now creating a new prototype database schema for GSAC, in case an agency lacks a database.  I am also writing code to read a SINEX file to load the GSAC database, and other code to read IGS site log files. 

    I plan soon to add to the GSAC web site to add to the installation help, including the MySQL .sql file which you can use to create a GSAC prototype database.   I expect to have the database schema .sql file on the web site by 25 July, and prototype scripts to read SINEX and IGS site logs soon thereafter.

    GSAC code on SourceForge will, hopefully, include new code to use the standard or prototype GSAC database, with a minimum of the code customization which is now required to install GSAC using a particular local existing database.   You can still use your existing database and install GSAC of course.  The prototype database is to ease installation, and also to provide a standard database schema well designed at UNAVCO for problem-free geodesy data repositories.


GSAC Workshop

    Discussions are underway, directed by Rui Fernandez, to hold a workshop in September which will do two things: install GSAC at one location, and provide an overview of installation for persons from one or more other agencies.   Date and location is as yet undetermined.   This will be a working workshop with most of the time doing operational coding at two or three keyboards, which of course will be very slow for anyone not doing the typing.  Also this goes against the experienced software engineer's dictum that "live demos (almost always) fail."   Nevertheless persons interested in installing GSAC might consider attending and should write to Rui.


Stuart Wier, science software engineer, UNAVCO