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The Sinex file is an ASCII formatted file written to comply with the Sinex standards as adopted by the IGS Central Bureau.
To implement the Sinex format a sinex.f subroutine has been written. This subroutine reads a-priori information from the site_info file. Solution estimates and the diagonal terms of the inverse are taken directly from the inverse matrix. This assumes that the inverse matrix is undisturbed so that all information for the global unknowns is present.
The reference epochs for the site unknowns in the SOLUTION/ESTIMATE section are given as the mean epoch for the observations of the site. Since the a-priori site coordinates are updated to the epoch of the observation as the observation equation is developed by the pages program, the adjusted site coordinates are also given at the mean epoch of the observations. To accomplish this the time shift, dt, from the mean epoch of observations for each site minus the sites reference epoch from the site_info file is multiplied times the a-priori site velocity and added with the a-priori coordinate and the solution adjustment to get the final site coordinate presented in the Sinex file.
Since updated a-priori site coordinates are used as noted above, the constrained site coordinates presented in the SOLUTION/APRIORI section are given for the mean epoch of the observations for each site. The coordinates are updated as noted above for the solution estimate except that the adjustment is not included. In addition the standard deviation is also updated to reflect the standard deviation of the apriori velocity. That is, dt is multiplied times the apriori standard deviation of the velocity and added to the standard deviation of the coordinate values before it is printed, providing an updated standard deviation (this step is not done for the solution estimate as the solution estimate is then based upon these apriori coordinates).
The Sinex file requires a SITE/ECCENTRICITY section which presumably should reflect the total eccentricity between the antenna reference point and the mark designated by the Domes number. Thus when the site_info file is read for use in sinex.f all components of the site offset are accumulated into one number for the eccentricity, these are the eccentricity portion of 'a' the antenna record, the offsets from the 'g' geocentric record which are transformed to NEU, and the offsets from the 't' topocentric record. In this accumulation certian assumptions have been made about the structure of the site_info file. These are that 1) the file is ordered by site, 2) within the various record types for a given site the records are ordered by the "effective date" for the specified information. Thus for a given date of the data being processed the values of the quantities are sequentially replaced with succeeding values untill the date of the data is reached. When the data for all the stations has been read then final eccentricity values are accumulated.
TOC | | | | Gpscom | INDEX