92 K.H. Neumayer
improvements were already obtained by simply migrating the processing software
from large shared-memory SunOS workstations to a cluster of high performance
Linux PCs. A more efficient treatment of clock parameters that emerge in GPS pro-
cessing allowed to increase the processing speed by a factor of up to two. Crucial
here was the exploitation of certain structures in the normal equation matrix. As
a side effect, the treatment of GPS measurements is now more or less similar to
the treatment of non-GPS data. An already existing column-block parallel compu-
tation method to obtain normal equation matrices from design matrices has been
augmented with a corresponding row-block parallel computation scheme. If those
new features are fully exploited on the high-performance Linux cluster of GFZ, the
gain in processing speed may reach a factor five to ten. A drawback is the need to
have large intermediary storage space, to use a large number of computation nodes.
The adopted method of choice to generate monthly gravity fields by stacking daily
normal equations has been transformed, by adding appropriate side constraints, to a
method to process satellite arcs of arbitrary lengths in a consistent manner.
Acknowledgment This is publication no. GEOTECH-1279 of the programme GEOTECHNO
LOGIEN of BMBF and DFG, grant 03F0436A.
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