GPS and GLONASS Concepts
A-5
GPS and GLONASS
Magnetic Model
The receiver uses the WMM-95 magnetic model. Grid size is 5 x 5 degrees, and the
interpolation technique is similar to the GPS ICD algorithm. Expected accuracy
depends upon the geomagnetic latitude. The errors are least at the equator, and
greatest at the magnetic poles, and equal to 0.5 degrees (RMS) when the actual
position is on a grid point. Expected accuracy when the actual position is halfway
between grid points is better than 2.5 degrees (RMS). In arctic and antarctic regions,
deviations from model values are frequent and persistent.
Comparison of GPS and GLONASS
Table A.1 compares the operating characteristics of GPS and GLONASS.
Table A.1: Comparison of GPS and GLONASS
Parameter
GPS
GLONASS
SIGNAL STRUCTURE
C/A Code (L1)
Code rate
1.023 MHz
0.511 MHz
Chip length
293 m
587 m
Selective availability
Yes
No
P Code
Code rate
10.23 MHz
5.11 MHz
Chip length
29.3 m
58.7 m
Selective availability
Yes
No
Encryption (anti-spoofing)
Yes
No
Signal separation
CDMA
FDMA
Carrier frequency
•
1575.42 MHz
•
1227.60 MHz
•
1602 + Kx9/16 MHZ, where K
is within the range -7 to +24
•
1246 + Kx7/16 MHz, where K
is within the range -7 to +24
SATELLITES
Number
24
24
Planes
6
3
Содержание GG Surveyor
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