• higher number of components of the received signal 
(Codes and Phases) (Leick et ah, 1998); 
• decreased times of static initialisation and dynamic re 
initialisation of the Rover receiver. 
Position DOP 
Fig. 2-b. GPS+GLONASS PDOP (from Contreras, 1998). 
1. INSTRUMENTATION 
Fig. 1. GPS+GLONASS satellite constellation on Oct. 14, 
1999. 
Position DOP 
Fig. 2-a. GPS PDOP (from Contreras, 1998). 
These new possibilities have permitted the extension of 
applications of satellite technology, especially to field 
surveys in which reception of the signal was often 
impossible with GPS receivers. 
This paper describes some applications of the RTK 
technique to combined GPS and GLONASS 
measurements on carrier phases LI and L2. 
These experiments involve: 
• marking out of transverse sections of a road 
embankment; 
• localising reference points in woodland for a water 
supply tunnel. 
These experiments demonstrate the advantages of 
GPS+GLONASS in terms of functionality, versatility and 
ability to operate in areas subject to high levels of 
disturbance. 
For the experiments, we used a GPS+GLONASS RTK 
surveying system composed of: 
• two field surveyor receivers (Legacy, Javad 
Positioning System) (Fig. 3) with 40 independent LI 
channels and 20 L2 channels able to record the GPS 
and GLONASS signals and to manage internally 
(with the Paradigm™ chip) the functions of Real 
Time calculation with firmware 2.0. 
Fig. 3. The Legacy receiver. 
The receivers were equipped with 16 MB of RAM 
memory, which permitted the separate management of 
storage of the signal (for eventual post-processing) and 
the functions of RTK calculation. The receivers possessed 
the JPS suppressor of the internal radio band of the CPU 
and the function of active CO-OP™ Tracking. This 
function allows the link of re-acquisition of the signal 
from Master to Rover with a time of less than 3 
milliseconds for all the satellites, temporarily blocked. 
Each of the 40 main channels of the Paradigm™ chip was 
also equipped with four Narrow anti-disturbance 
correlators. In practice, 160 continuous search chips, 
active in the phase of recording both the GPS and 
GLONASS signal, provide a 13-fold reduction of the 
times of static initialisation or dynamic re-initialisation 
with respect to the times of conventional GPS receivers 
with 12+12 independent L1+ L2 channels.