SUMMARY
The paper shortly describes the ultra-rapid orbits of GPS satellites and their potential
applications in real-time monitoring of position variations. The processing procedure for near
real-time network solution using precise orbits is explained. With the recent accuracy of the
ultra-rapid ephemerides using their predictions the network in near real-time with
unprecedented reliability can be processed and thus can be used for monitoring of stability of
the individual stations or the whole network. These results can be further improved by
Kalman filtering approach. The near real-time solution has been tested at Department of
Theoretical Geodesy at the Slovak University of Technology. An experiment with a device
which allowed performing antenna horizontal displacements with exactly measurable
magnitude is discussed in the last chapter of the paper. Our approach enables to detect sub-
centimeter displacement in several hours after the event at sites in distances of tens of
kilometers from the nearest network station.