1. In contrast, GNSS network architectures often make use of multiple reference stations . 2. The system requires an extensive network of reference stations , and constant maintenance. 3. The license for the above-referenced station will expire on October 1, 2013. 4. In the following years, it became a reference station in Spain. 5. The team established the first continuous-tracking GPS reference station in Antarctica. 6. "' Virtual Reference Station "'( VRS ) networks use Global Navigation Satellite Systems. 7. In 2010 GLONASS differential reference station started to work in Novolazarevskaya. 8. The reference station also provides Internet to Novolazarevsklaya personnel. 9. Operational reliability and accuracy depend on the density and capabilities of the reference station network. 10. Signals from core satellite are received by ground reference stations and any errors in the signals are identified.