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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.
Parameter
C/A Code (L1)
Code rate
Chip length
Selective availability
P Code
Code rate
Chip length
Selective availability
Encryption (anti-spoofing)
Signal separation
Carrier frequency
Number
Planes
GPS and GLONASS Concepts
Table A.1: Comparison of GPS and GLONASS
GPS
SIGNAL STRUCTURE
1.023 MHz
293 m
Yes
10.23 MHz
29.3 m
Yes
Yes
CDMA
•
1575.42 MHz
•
1227.60 MHz
SATELLITES
24
6
GLONASS
0.511 MHz
587 m
No
5.11 MHz
58.7 m
No
No
FDMA
•
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
24
3
A-5
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