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COMMON FILES

Files required by run_survey which are provided by the user.

Position/Offset/Met (POM) files
REQUIRED
LOCATED IN THE files DIRECTORY

POM files provide the most basic site information: position, offset, surface met, and antenna type. Generally, this basic information will be superseded by other sources, but the POM files guarantee this basic information exists. Moreover, POM files provide a quick and dirty means of providing site information for circumstances the initial determination of coordinates of a new site.

POM files use the naming convention CCCC.pom, where CCCC is the four character site ID. This site ID must match that used in the RINEX "o" file name. For example, wes2.pom is the valid POM file name for wes2, the Westford, MA site. Internally, the wes2.pom file would look like:

    1492233.406   -4458089.552    4296046.098
           .000           .000           .110          -.018
         15.000        980.000         75.000
          4 

where each line is:

1. is the XYZ coordinates, in meters, of the Antenna Reference Point (ARP).
   
2. contains the north/east/up offset from the ARP to the L1 phase center of the antenna. The fourth number is the L1-L2 height difference. Again, all values are in meters.
   
3. is the surface met values in this order, temperature, pressure and relative humidity. The units are degrees C, millibar and precentage of saturation respectively.
   
4. is the antenna type identifier and must match an entry in the antenna phase correction file.

editdb.par
REQUIRED
LOCATED IN THE files DIRECTORY
NGS users will automatically access a standard file stored in /ngslib/data/GPS directory

editdb.par contains the parameters defining the operation of the auto-editing program, editdb. The format of this file is:

 0  10  20  20  0.1   0.1  0.5  0

These parameters are:

1. 0 = do not make any plots, 1 = make dda# & wla# plots;
2. the number of points in a cell (the data are subdivided into smaller groups, or cells, for detailed analysis);
3. the size of the gap (in epochs) that restarts a bias in pages;
4. the minimum epoch span to solve for a bias;
5. the RMS (in cycles) for a cell to initiate remediation;
6. the maximum fraction difference from integer for cycle slip solution;
7. the maximum double difference slope allowed within a cell;
8. 0 = do not write diagnostic file, 1 = write diagnostic file;

fixsite.inp
REQUIRED
LOCATED IN THE files DIRECTORY

Four character site ID's, one per line, are read from this file. These listed sites will be constrained in the baseline estimates. At least one site should be listed although more than one is permitted. If a site ID appears here but has no data, that ID is ignored.

hubsite.inp
If none is proved, the fixsite.inp file will be used.
LOCATED IN THE files DIRECTORY

Four character site ID's, one per line, are read from this file. In the processing, sites not listed in this file are forced to form baselines with at least one site listed in the hubsite.inp file. This file gives the user some control over the structure of the network automatically created during the processing. Typically, but not necessarily, constrained sites and reliable, well-determined sites are included in this file.

file of antenna phase corrections
REQUIRED
LOCATED IN THE files DIRECTORY
NGS users will automatically access a standard file stored in /ngslib/data/GPS directory

Each antenna type has a unique gain pattern resulting from its physical structure and electronic characteristics. This characteristic is endemic to all antennas and will change observed pathlengths. Most GPS antennas in use today have azimuthally homogeneous patterns. The remain elevation dependence can mimic and corrupt the tropospheric effects. Under many conditions when identical antenna types are processed together in software which does differencing (as pages does), the antenna characteristics will difference away. However, when processing data from two or more antenna types these antenna patterns, aliased through the tropospheric correction, result in significant, erroneous positions. Like the troposphere, these errors predominately alias into the height estimate.

The antenna phase pattern models contained in this file are used to minimize this effect. Generally, these models would come from a standard source such as National Geodetic Survey or the International GPS Service for Geodynamics.

site information file
OPTIONAL
DEFAULT LOCATION IS THE files DIRECTORY OR SPECIFIED BY USER
NGS users will automatically access standard files stored in /ngslib/data/GPS directory

Files containing a history of coordinates and equipment can be used to supersede the basic info provided in the POM files. These file's format is binary and can be created, maintained, viewed and modified with the xsites program.

leap_seconds (Unix or Linux)
leapsec.dat (Windows NT)
REQUIRED
DEFAULT LOCATION IS THE files DIRECTORY
NGS users will automatically access a standard file stored in /ngslib/data/GPS directory

The leap_second file provides the dates of all leap seconds which have occurred since the start of GPS time (January 6, 1980). Effectively, this is the difference between Coordinated Universal Time (UTC) and GPS time. The file is a simple ASCII file.

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