Chapter 2 - Introducing the Northstar 951/952
951/952 Operator’s Manual Rev. B
Page 27
tor instructs the DGPS receiver to switch automatically to
other available satellites.
The 951XD/952XD contains an internal, fully automatic differ-
ential receiver. The 951X/952X doesn’t have an internal differ-
ential receiver, but can accept corrections from an external
differential receiver, such as the Northstar 8401 or 8800.
Loran
Loran can outperform non-differential GPS in
repeatable accu-
racy
. Although susceptible to weather and limited to coastal
use, it’s a dependable system familiar to thousands of boaters.
Since the 1970’s, loran users have relied on this system’s abil-
ity to repeatedly return them to a previously saved location
with extreme accuracy. Fishermen have especially appreciated
this capability because each subsequent visit to a lobster trap
or buoy was virtually “on the mark,” saving them valuable
time and money. Loran’s
repeatable accuracy
was superior to
anything else commercially available at the time.
In very good coverage areas, loran can typically get you within
50 feet (or approximately 14 meters) of your previously visited
target. On the other hand, uncorrected GPS can only be
counted on to get you to within about
100 feet
(20-30 meters),
maximum, of your intended destination. Obviously then,
uncorrected GPS wouldn’t be as much help in finding a mark
in dense fog. Since most loran chains were configured for opti-
mum coastline navigation, it’s easy to see why loran’s repeat-
able accuracy has served harbormasters and fishermen so well
for the last 25 years.
Loran, however, isn’t as proficient as GPS in
absolute accuracy
,
or when visiting a spot for the first time. Because loran trans-
mits at a relatively low frequency (100 kHz—similar to that of
your AM radio), your ability to get an accurate position “fix” is
directly related to:
•
your distance and line geometry from the loran transmit-
ters
•
the weather between you and the transmitters
In these two areas GPS consistently excels when it comes to
absolute accuracy.
Summary of Contents for 951
Page 6: ...Page iv 951 952 Operator s Manual Rev B ...
Page 8: ...Page vi 951 952 Operator s Manual Rev B ...
Page 10: ...Page viii 951 952 Operator s Manual Rev B ...
Page 24: ...Page 14 951 952 Operator s Manual Rev B Chapter 1 Quick Start ...
Page 40: ...Page 30 951 952 Operator s Manual Rev B Chapter 2 Introducing the Northstar 951 952 ...
Page 50: ...Page 40 951 952 Operator s Manual Rev B Chapter 3 Using the Controls ...
Page 124: ...Page 114 951 952 Operator s Manual Rev B Chapter 7 Creating Routes ...
Page 136: ...Page 126 951 952 Operator s Manual Rev B Chapter 8 Understanding Waypoint Route Navigation ...
Page 154: ...Page 144 951 952 Operator s Manual Rev B Chapter 10 Using Other Special Functions ...
Page 184: ...Page 174 951 952 Operator s Manual Rev B Chapter 11 Customizing the Unit ...
Page 188: ...Page 178 951 952 Operator s Manual Rev B ...
