International Metrology Symposium (RMO 2008), November 12-15 2008l, Cavtat, Croatia

1. NATIONAL TRACEABILITY OF GPS
MEASUREMENTS
IN THE REPUBLIC OF SERBIA
Vukan Ogrizović, Violeta Vasilić,
Siniša Delčev, Jelena Gučević
Belgrade University
Faculty of Civil Engineering
Department for Geodesy and Geoinformatics

2. Company
Logo Serbian Time and Frequency Standard
 Caesium atomic clock Agilent 5071A
 Nominal accuracy ±10-12
 12 years warranty
 Expected age of the beam up to 20 years
1st International Simposium RMO 2008 2/10

3. Company
Logo Serbian Time and Frequency Standard
Agilent
5071A
Cs clock
antenna
5 MHz
TST 6490A
Microphase 5MHz
stepper
10 MHz TST 6460 TTS-2 GPS
Digital clock receiver
Agilent Ref. point
5087A UTC(ZMDM) 1 pps
Distribution
amplifier TST 6487
Distribution
amplifier
1 pps 1
pps
10 MHz
10 MHz
5 MHz
1st International Simposium RMO 2008 3/10

4. Company
Logo National traceability chain
D
U T C and
SI Second
(B IP M )
1 pps
G PS
A
U TC
(D M D M )
E
B
U TC
(M L 1 6 0 )
 Completion of link B: C
 Broadcast service
 Comparing 1PPS signals EN D
U SER 1
EN D
U SER 2
... EN D
U SER 3
1st International Simposium RMO 2008 4/10

5. Company
Logo Experiment setup
AT AR
T R IM B L E
NETR S DUT
1 pps 1 p ps
In p ut A In p u t B
H A M E G H M 8 12 3
T IM E
serial po rt
A’ B
PC
d ata lo g g in g
1st International Simposium RMO 2008 5/10

6. Company
Logo Measurement of a time difference
 Time interval mode
 Offset between start pulse and stop pulse
 Analysis of time differences
1 pps
t
S ta rt
S to p
T im e
1st International Simposium RMO 2008 6/10

7. Company
Logo Measurements
difference [ns]
200
100
0
-100
-200
-300
0 500 1000 1500 2000 2500
time [s]
Raw measurements
350
300
250
frequence
200
150
100
50
0
-150 -100 -50 0 50 100 150
range
Frequency histogram
1st International Simposium RMO 2008 7/10

8. Company
Logo Results
Allan’s variances:
1/ 2
 1 M −2 2

σ y ( 2, τ ) =  2 ∑(x i+2 − 2 xi +1 + xi ) 
 2τ ( M − 2)
 i =1 

2
1 N − 3 n +1  j + n −1 
mod σ 2 ( τ) = ∑  ∑ ( xi + 2 n − 2 xi + n + xi ) 
y
2n 2 τ 2 ( N − 3n + 1)  
j =1  i= j 
μs
for τ = 6s, Mod σ y ( τ ) = 0, 267
s
μs
for τ = 8s, Mod σ y ( τ ) = 0, 201
s
μs
for τ = 10s, Mod σ y ( τ ) = 0,159
s
1st International Simposium RMO 2008 8/10

9. Company
Logo Conclusions and recommendations
 Traceability from working standards to NMI and BIPM
 Link from ML160 to UTC(ZMDM) should be established
 Comparison of ML160 to UTC(ZMDM) 1PPS output
 24 hours long logging session
 Implementation of real-time calibration procedure
1st International Simposium RMO 2008 9/10

10. Company
Logo THANK YOU!
Our participation on RMO2008 is supported by:
Faculty for Civil Engineering, Belgrade
htpp://www.grf.bg.ac.yu/
Metrological Laboratory ML160, Belgrade
htpp://ig.grf.bg.ac.yu/metrolab/
1st International Simposium RMO 2008 10/10