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1.Creating A PAGES Work Area
2.Downloading GPS Data
3.Downloading an Ephemeris
4.Selecting Sites To Hold Fixed
5.Creating The POM Files
6.Running run_survey
7.Manually Modifying The Processing


run_survey expects a specific directory structure, or tree. Although the general structure is fixed, the name of the base of that tree is input by the user via the command line; therefore the base of the processing tree can originate anywhere. The directory or directories where the actual processing will occur, or working directories, are named yr_doy, where yr is the two digit year when the data were taken and, separated by an underscore, doy is the three digit day-of-year. The files directory stores files common to all processing for this project. This directory structure has proven to be self-descriptive, simplify archiving, and help prevent contamination of one project's processing with another's. The figure below shows the generic structure of this tree:

where "yr_dy1/" , "yr_dy2/" and "yr_dy3/" are directories where data processing, from individual sessions, days, occupations, etc., will occur. As shown above, there may be one or more of these working directories. "files/" is a special subdirectory where files specific to these data are kept. The intent is to force the user to group related data processing together under a meaningfully named directory.


These tutorials describe the most basic processing of a single day's data: February 2, 2001 or 01/033. To setup the processing directory tree, first change to the directory where this tree will be created. In this example, it is assumed that this will be your home directory but remember, any directory in which subdirectories can be created is acceptable.
cd ~

Now create the base of the processing tree.

mkdir Tutorial
cd Tutorial

Next, create the working and "files" directories.

mkdir 01_033
mkdir files

Now change to the "files/" directory.

cd files

Only a single external file is required in this basic scheme, the antenna phase pattern model and offsets information file. For brevity, this file will be called the ant info file hereafter. Antenna measurments of this type are on-going research efforts by several groups.  The most comprehensive table of antenna pattern models is available from the NGS and will be used in this tutorial. A copy of the NGS ant info file can be found at the software distribution site and as part of the archive file containing the data used in these tutorials. Regardless of the source, the ant info file should be copied into the "files" subdirectory.

cp ~/Somewhere/ant_info.003 .

With on-going projects, periodically updating of the ant info file is strongly recommended. For now, go back down to the base of the processing tree. Additional files will be created in or added to this directory later.
cd ..


The ant_info.003 file contains standard models for correcting observation elevation dependent variability in the location of the phase center of a GPS antenna. The measurements which constitute the entries in ant_info.003 are an on-going project at the NGS. A description of this project and up-to-date file can be retrieved from the NGS web site.

The directory should now look like:

Tutorial Directory Tree

"01_033/" is currently empty.  "files/" contains only the ant info file, ant_info.003.

2009-02-15 18:41 UTC