Bernese GPS Software Version 5.0 - Bernese GNSS Software

19. Bernese Processing Engine (BPE)
benefit from this redundancy. In the panel “MKCLUS 3: Regional Cluster Definition Options (Zero
Differences)” the program MKCLUS provides the possibility either to define the maximum
number of observation files in a cluster or the number of clusters. The distance between the
stations in a cluster is minimized.
If the satellite clocks are estimated in a regional cluster there are always satellites that
are observed by one station only. The residuals for those observations will be zero but this
tells nothing about the quality of the observations itself. For the screening of the post-fit
residuals of all observations a “Minimum number of observations per satellite at each epoch” may
be defined with a value bigger than 1. As a consequence a number of observation files will
be assigned to more than one cluster.
19.12.2.3 Global Clusters for the Zero-Difference Processing
The main application of processing zero-difference observations files in global clusters is
the computation of receiver and satellite clocks. One global solution created in a single
run of the program GPSEST is of course the best way for clock estimation because all
correlations can be considered. In order to include more stations into the solution the
zero-difference observation files may be divided into a number of global clusters that are
processed independently with program GPSEST. In each global cluster solution a different
set of stations is used to estimate the satellite clocks. The program CCRNXC can be used
to combine the clock corrections from the individual cluster solutions to a consistent global
solution.
The program MKCLUS provides several options to generate global clusters from a list of
zero-difference observation files. The “Number of clusters” and the “Maximum number of stations
per cluster” can be specified by the user in panel “MKCLUS 3: Global Cluster Definition Options
(Zero Differences)”. If more observation files are specified a selection of stations that are
used in the global clusters for processing is possible. The criteria are described above. In
addition a minimum number of observations to each satellite can be requested in option the
“OBSERVATION REDUNDANCY” to achieve a reliable satellite clock estimation.
19.12.3 Rejecting Stations from the Definition of the Geodetic Datum
In an automatic processing it might be important to automatically reject reference stations
from the definition of the geodetic datum if a significant difference is found between estimated
and a priori coordinates. Examples are bad tracking data, unannounced antenna
change, or shift of the station due to an earthquake. Such outliers may be detected by comparing
coordinates of reference sites obtained with a no-net translation condition with the
a priori coordinates using program HELMR1 (see Section 10.6.2). The program can be used
to identify outliers and to write a new station selection file containing only those stations
that passed the outlier criterion.
If reference stations are identified as outliers the datum definition for the final solution has
to be repeated with the modified station selection list by jumping back to the appropriate
position in the processing sequence. The jump can be triggered by the existence of an
outlier list that may be written by program HELMR1. This quality monitoring feature is
demonstrated in the BPE example RNX2SNX delivered with the software, see Section 20.4.2.
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