GPS C/A Code Signal Structure - Fundamentals of Global Positioning System Receivers: A Software Approach - page 91

on hour boundaries except for the first data set of a new upload. The first
data set may be cut in at any time during the hour and therefore may be
transmitted by the satellite for less than one hour. Additionally, the t oe
value for at least the first data set transmitted by a satellite after an upload
will be different from that transmitted prior to the cutover.
2. The rest of the ephemeris data : These are listed in Tables 5.9 and 5.10.
3. Spare and reserved data fields : In subframe 2 bit 287 is reserved and
bits 288 - 292 are spared. All spare and reserved data fields support valid
parity within their respective words. Contents of spare data fields are
alternating ones and zeros until they are allocated for a new function.
Users are cautioned that the contents of spare data fields can change with-
out warning.

TABLE 5.9 Ephemeris Parameters in Subframe 2

Number
of
Bits

Scale
Factor
(LSB)

Effective
Range Parameter Location Units

IODE 61 - 68 8 (see text)

2 − 5

C rs : Amplitude of the
sine harmonic
correction terms to
the orbit radius

69-84 16 meters

16 ∗ 2 − 43 n : Mean motion

difference from
computed value

91 - 106 semicircles/sec

32 ∗ 2 − 31

M 0 : Mean anomaly at
reference time

107 - 114; 121 - 144 semicircle

16 ∗ 2 − 29 C uc : Amplitude of the

cosine harmonic
correction term to
the argument of
latitude of
argument of
latitude

151 - 166 radians

2 − 33

e s : Eccentricity 167 - 174; 181 - 204 32 dimensionless

0.03

16 ∗ 2 − 29

C us : Amplitude of the
sine harmonic
correction term to
the argument of
latitude

211 - 226 radians

√ a s : Square root of
the semimajor axis

2 − 19 meters 1 / 2

227 - 234; 241 - 264 32

2 4 t oe : Reference time

ephemeris

277 - 286 16 604,784 seconds