GPS Receiver-Related Subjects - Fundamentals of Global Positioning System Receivers: A Software Approach - page 307

these data through a Matlab program ( 1 ) . A discussion on finding the available
satellite positions from almanac data is presented in Section 12.12. Programs can
be also found on the Internet that provide satellite information. For example, one
of these internet locations is http://sirius.chinalake.navy.mil/satpred/ .
The number of available satellites and their carrier frequencies are of most
interest here. An example will be used to illustrate the use of the YUMA data. In
this example, an arbitrary time of year 2002, April 25, 8 : 04 AM, is selected, and
the user position is Dayton, Ohio. The purpose is to find the available satellites
and their Doppler frequencies. This particular time is associated with YUMA data
139, where 139 represents the week number. The number of satellites and their
Doppler frequencies can be calculated from several YUMA data sets besides
YUMA data 139. Four YUMA data sets 127, 138, 139, and 140 are used to

TABLE 12.1 Doppler Frequencies Calculated with Different YUMA Data

Reference: Time: 2002 April 25, 8 o'clock AM 04 min 00 sec

Location: Latitude: 39.7772 Longitude: − 84.0821 Altitude: 179.2

1 2 3 4 5 6 7 8

YUMA
Data 139 138 140 127

Frequency
Off

Frequency
Off

Frequency
Off Doppler Doppler Doppler Doppler

Satellite Hz Hz 139 - 138 Hz 139 - 140 Hz 139 - 127

− 2181

2

4 3928 3930 − 2 3925 3 3924 4

7 1525 1547 − 22 1503 22 1826 − 301

8 − 2647 − 2613 − 34 − 2683 36 − 2250 − 397

11 − 1507 − 1469 − 38 − 1546 39 − 1045 − 462

20 2698 2705 − 7 2689 9 2736 − 38

26 − 1528 − 1491 − 37 − 1567 39 − 1015 − 513

27 − 3686 − 3670 − 16 − 3702 16 − 3466 − 220

28 803 826 − 23 780 23 1066 − 263

29 283

31 − 3274 − 3279 5 − 3270 − 4 − 3319 45