START

COLD

YES

ADD 6 MINS FOR

START

CLOCK WARM UP

NO

YES

ADD 15 MINS FOR

ALMANAC

TO COLLECT

CLEARED

ALMANAC

NO

P.V.T.

PVT UNCERTAINTIES

UNCERTAINTIES

NO

LARGE ADD 30 SECS

VERY

ALMANAC

SMALL

YES

P <100km

V < 75m/s

UNCERTAINTIES

YES

SMALL ENOUGH TO ALLOW

A <10m/s

2

P <10km

DIRECT P CODE ACQUISITION

T <20s

OR ATOMIC AIDING

V 

 0

A 

 0

J 

 2m/s

3

T <10

s

NO

CA TO `P'

DIRECT `P'

ACQUISITION

CODE ACQUISITION

ADD 60 SECS

ADD 30 SECS

(TTFF2)

(TTFF1)

COLLECT EPHEMERIS ADDS

CURRENT

3

MINS FOR 1 CHAN SET

EPHEMERIS

2

MINS FOR 2 CHAN

IN SET

30

SECS FOR 5 CHAN

1

MIN FOR MULTIPLEX

YES

FINISH

Figure 3 2.  Time To First Fix (TTFF)

3 12