NorthStar 941X User manual

Northstar 941X
Reference Manual
SOFTWARE VERSION 2.05
30 SUDBURY ROAD
ACTON, MASSACHUSETTS 01720
[phone]
Copyright 1994, 1995, 1996 Northstar Technologies P/N GM1100 Doc. Rev D

WARRANTY
Northstar Technologies, a Division of CMC Electronics, Inc., warrantees its products
to be free from defects in material and workmanship for a period of two (2) years
from the date of shipment to an authorized dealer. This warranty applies to the
original purchaser or subsequent owner.
This warranty covers repair and/or replacement, at our option, of any part or parts
found tobe defective, provided such defects in our opinion are due to faulty material
or workmanship and are not caused by tampering, abuse, or normalwear.
All warranties are F.O.B.: Northstar Technologies
30 Sudbury Road
Acton, Massachusetts 01720
This warranty applies only to products in normal use. It does not apply to units or
circuit boards defective due to improper installation, physical damage, tampering,
lightning or other electrical discharge, receivers or mainframes subjected to fresh
water or saltwater immersion*, units with altered serial numbers, or units repaired
by unauthorized persons or in violation of Northstar service procedures.
The foregoing are the only warranties expressed or implied. No other warranty
exists.
Northstar assumes no responsibility for any consequential losses or damages of any
nature with respect to any products or services sold, rendered, or delivered.
*Certain Northstar control heads are warranty protected against damage due to
water leakage, provided the head has not been tampered with.

IMPORTANT NOTICE
Although Northstar products are designed to be very useful navigation tools, they
are not substitutesfor good seamanship. The prudent navigator should never rely on
any single device as the sole source of navigation guidance. Exercise caution and
good judgment whenever underway.

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C
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CONTENTS
ONTENTSONTENTS
ONTENTS !
The Northstar 941X
The Northstar 941XThe Northstar 941X
The Northstar 941X
Introduction .................................................................2
Upon First Start-up ......................................................2
Using This Manual........................................................3
941X Features...............................................................4
941X Functions.............................................................5
Comparing GPS and Loran ..........................................5
Mounting Basics ...........................................................9
Special Functions..........................................................9
The Display Screen.....................................................10
Interfacing Capability..................................................11
Using the Controls
Using the ControlsUsing the Controls
Using the Controls
POWER Key................................................................ 14
CONTRAST Key.......................................................... 14
SAVE/MOB Key...........................................................15
Function Keys............................................................. 16
Menu Keys....................................................................17
Cursor Keys..................................................................17
Keypad .........................................................................17
Special Display Windows ...........................................18
Basic Navigation
Basic NavigationBasic Navigation
Basic Navigation
Displaying Position, Heading & Speed ......................22
Position Plotter...........................................................22
Using GPS...................................................................25
Using DGPS ................................................................26
Using Loran ................................................................30
Using Phantom Loran ................................................32
1
2
3

Creating Waypoints and
Creating Waypoints andCreating Waypoints and
Creating Waypoints and
Routes
RoutesRoutes
Routes
Entering Data..............................................................36
Creating Waypoints....................................................37
Avoidance Areas .........................................................39
Waypoint Lists............................................................ 41
Coordinate Options ....................................................42
Updating Waypoint Coordinates ...............................42
Editing Waypoints......................................................43
Transferring Waypoints to a PC.................................44
Creating Routes ..........................................................44
Saving a Route ............................................................47
Changing a Route........................................................50
Waypoint & Route Navig
Waypoint & Route NavigWaypoint & Route Navig
Waypoint & Route Naviga
aa
ation
tiontion
tion
Quick-Start Waypoint.................................................54
Navigating to Waypoints............................................55
Navigating Along Routes............................................59
Restarting the Course Line......................................... 61
The NAV LOG Function
The NAV LOG FunctionThe NAV LOG Function
The NAV LOG Function
What NAVLOG Does..................................................64
Logging Your Trip.......................................................65
Changing Your Trip ....................................................65
Adding Waypoints to the Trip....................................66
4
5
6

Other Special Functions
Other Special FunctionsOther Special Functions
Other Special Functions
Alarms.........................................................................68
Screen Backlighting.....................................................71
TideTrack™..................................................................71
Internal Differential Beacon Receiver .......................74
Customizing the 941X
Customizing the 941XCustomizing the 941X
Customizing the 941X
Time of Day.................................................................78
Display Options ..........................................................78
Navigation Options.....................................................82
Receiver Options.........................................................87
Port Setup Options .....................................................90
Service Options........................................................... 91
Geodetic Datum..........................................................94
Installation and Interfacing
Installation and InterfacingInstallation and Interfacing
Installation and Interfacing
Mounting the 941X...................................................100
Wiring the 941X System...........................................102
Antenna Location .....................................................104
DGPS Antenna Coupler (ACU).................................108
Interfacing the 941X..................................................112
Programming the Output Ports ................................115
Appendix
AppendixAppendix
Appendix (Specifications) ........................................ 129
Glossary
GlossaryGlossary
Glossary..................................................................... 135
Index
IndexIndex
Index .........................................................................138
7
8
9

Figures
FiguresFigures
Figures
FIGURE 1—MAX. POSITION VARIANCES WITH UNCORRECTED GPS....8
FIGURE 2—YOKE MOUNT DRILLING DIMENSIONS...........................102
FIGURE 3—REAR CONNECTORS ......................................................103
FIGURE 4—941X GPS-ONLY ANTENNA (AN145 & AN150)..........105
FIGURE 5—941X COMBO GPS/DGPS ANTENNA (AN190).............105
FIGURE 6—STRIPPING THE COAX CABLE JACKET............................107
FIGURE 7—FLARED CABLE BRAID ..................................................108
FIGURE 8—COMPLETED BNC CONNECTOR ....................................108
FIGURE 9—ACU ASSEMBLY...........................................................110
FIGURE 10—PL 259 (UHF) CONNECTOR........................................111
FIGURE 11—INTERFACE CONNECTOR (MATING SIDE)......................113
FIGURE 12—200 PPNM OUTPUT BLOCK DIAGRAM........................115
FIGURE 13—941X DIMENSIONS ......................................................132
Tables
TablesTables
TablesTABLE 1—DATUM LIST.....................................................................97
TABLE 2—INTERFACE CONNECTOR PINS ........................................114
TABLE 3—PORT SETUP OPTIONS.....................................................116
TABLE 4—NMEA 0183 SENTENCE IDENTIFIERS.............................120
TABLE 5—CONNECTION TO NORTHSTAR 800 PORT A.....................123
TABLE 6—CONNECTION TO NORTHSTAR 800 PORT B.....................123
TABLE 7—NORTHSTAR 800 SERIES OUTPUT PORT SETUP...............123
TABLE 8—YEOMAN ELECTRONIC PLOTTER SETUP WITH 941X.......124
TABLE 9—CONNECTING TO EXTERNAL NS BEACON RECEIVER......125

Rev. D 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Page 1
Introduction 2
Upon First Start-up 2
Using This Manual 3
Features 4
Functions 5
Comparing GPS and Loran 5
Mounting 9
Special Functions 9
The Display Screen 10
Interfacing Capability 11
his section introduces you to the Northstar 941X navi-
gator, outlining its various operational functions, in-
stallation configurations, and specifications.
Use this section to get a quick overview of what the 941X is
all about, and how you can use it to your best advantage.
1
Introducing the Northstar 941X
T

Page 2 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Rev. D
HE NORTHSTAR 941X combines 12-channel GPS navigation with
Differential GPS capability, a high-definition display, loran compati-
bility, built-in tide data up to the year 2010, and many other navigation
features.
For the ultimate in GPS accuracy, the 941X may be purchased as the
941XD, featuring an internal DGPS (Differential GPS) receiver. This ad-
vanced system gives you even greater accuracy by accepting Differential
GPS signal “corrections” from shore-based transmitters (called “bea-
cons”), and using them to display position fixes as accurate as 2-5 me-
ters. You can also connect your 941X to any external source of DGPS
corrections meeting the SC-104 standard (such as the Northstar 8800
DGPS Sensor).
When you turn your 941X on for the very first time, you may be greeted
with a flashing exclamation point symbol in the lower right portionof the
GPS POSITION screen, and the word ACQUIRE or SKY SEARCH in
the status box at the top. The flashing exclamation point simply means
that an alarm message is present and waiting for your acknowledgment.
To see the message, press the STAR key once. The ALARMS AND
BACKLIGHT screen will be displayed.
Introduction T
Upon First
Start-up

Rev. D 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Page 3
The alarm message NO GPS POSITION FIX, along with its time and
date, are shown in the RECENT ALARMS box. The word NEW in the
upper right corner of the box indicates that this is a previously unac-
knowledged message.
This sequence is a normal part of powering-up the 941X for the first
time, as it notifies you that it is in the process of acquiring satellite in-
formation necessary for navigation. It normally takes only two to five
minutes to acquire this data, after which the 941X is ready to navigate.
(This alarm condition usually occurs in units shipped to customers lo-
cated more than several hundred miles from the Northstar factory, and
only the first time the 941X is turned on after being installed.)
Press the CLEAR ALARM menu key to the right of the display screen to
acknowledge and clear the message. Press the POSITION key below the
left of the screen to return to the main GPS POSITION screen. The 941X
is now ready to navigate. (For more on alarms, see page 68. If you wish
to proceed directly to navigating with the 941X, skip to page 22.)
Your 941X was designed to be an easy-to-use, full-function GPS naviga-
tor, understandable in the information it displays and dependable in its
performance. This Reference Manual is intended to complement that
ease of use by illustrating and describing the 941X’s various functions in
a format helpful to quick learning and safe operation.
The sections in this manual are grouped by related functions, beginning
with an overview of basic control panel layout and function commands,
and gradually progressing to more advanced waypoint and route naviga-
tion operations. Sample screen images are used throughout to help il-
lustrate what the 941X display screen looks like for the function being
described.
The “helpful hand” (pictured at left) is a convenient shortcut that leads
you directly to step-by-step instructions. You can also use it as a quick-
reference for locating less-frequently-used operations.
Using This
Manual
"

Page 4 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Rev. D
Upon using the 941X, you’ll see that you can actually learn to operate the
system’s various features without constant referral to this manual. After
you’ve read through it once, you won't have torefer toit very often again.
Since the 941X anticipates your most frequent requests for navigation
information, accessing most functions requires only one or two button
pushes. By minimizing the attention needed to navigate, you can now
devote more time to other aspectsof your trip.
•accurate, worldwide position data inany weather,24 hours a day
•optional internal DGPS (Differential GPS) Beacon Receiver for
accuracy as good as 2-5 meters
•fast signal acquisition
•fast-reacting, accurate speed and course
•lat/lon display
•built-in plotter shows:
1) your position relative to nearby waypoints;
2) your recent track line;
3) your intended course line; and
4) avoidance areas,
all against a latitude/longitude grid.
•tide prediction software integrated with navigation display (at
any NOAA tide station; for today or any other date.)
•stores up to 1,000 waypoints and 500 routes
•displays waypoints:
1) in alphabetical order
2) in order of distance from your present position
3) saved with the SAVE
button
4) stored as avoidance points
•plots position of:
1) nearby waypoints
2) routes
3) avoidance areas
Features
GPS features
navigation
features
waypoints and
routes

Rev. D 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Page 5
Five keys on the 941X instantly select the most commonly used func-
tions, as described below:
POSITION displays position coordinates as
1) GPS lat/lon coordinates
2) loran TDs, if you have a loran receiver interfaced to the unit
3) or calculated “Phantom Loran” TDs if you don't.
Speed- and Course-Over-Ground, and Time and Date are also displayed.
An alternate position screen plots your position graphically, along with
any nearby waypoints and your track history.
STEER shows how to steer precisely along a course line to your current
waypoint. It also displays your Cross Track Error, Estimated time to
waypoint, Estimated Time of Arrival, Course Over Ground, Speed Over
Ground, Speed of Advance, etc.
() (The STAR key) displays alarm conditions and tide information,
and accesses setup functions for customizing the operation and displays
of your 941X, including screen brightness.
WAYPTS/ROUTES lets you enter or access waypoints and routes for
navigation.
NAV LOG displays the progress of your current navigation plan (today’s
trip) and lets you modify it.
In addition to these function keys, the SAVE/MOB key instantly saves
your position as a waypoint, and provides a Man Overboard function for
returning to the saved point.
Five MENU KEYS on the right edge of the display are used to select be-
tween specific choices displayed on the screen.
The nation’s GPS system has received much publicity, often described as
providing the ultimate in navigation accuracy for all applications. Its
major advantage over all other commercially-available navigation sys-
tems, including loran, is its all-weather, worldwide availability and
ab-
solute accuracy
. (
Absolute accuracy
refers to the ability of a navigation
device to determine your actual latitude and longitude coordinates on
the surface of the earth, as compared to position information determined
Functions
Comparing GPS
and Loran

Page 6 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Rev. D
from a chart or other reference.
Repeatable accuracy
refers to the ability
to return to a position whose coordinates you have previously recorded
with the same equipment.)
Developed by the United States Department of Defense (DOD) the GPS
system of 21 active satellites (with 3 additional spares) literally encircles
the earth with navigation information. GPS is offered in two forms: for
military users and for civil users.
With GPS available to virtually anyone around the world, the DOD
wanted to avoid the possibility that its precision could be used by hostile
forces as a source of accurate targeting data against U.S. interests. To
guard against such actions, they introduced intentional errors into the
GPS signals that only U.S. forces could bypass. Called
Selective Avai
Selective AvaiSelective Avai
Selective Avail
ll
l-
--
-
ability
abilityability
ability
(or SA), it involves a complex formula of data encryption that can
be turned on or off without the end-user ever knowing for sure whether
it is in effect or not. DOD’s stated position is that SA will remain in effect
indefinitely.
Selective Availability effectively reduces GPS’s absolute and repeatable
accuracy from 30 meters (roughly 100 feet) 95% of the time, to 100 me-
ters (330 feet) 95% of the time. This means that, with SA, you can expect
to be within 300 feet of your intended position 95% of the time, and be-
yond that area approximately 5% of the time. At first, this was accepted
by most end-users as an inevitable part of GPS, a tradeoff against its
global availability. But it didn’t meet the Coast Guard’s requirement of 8-
20 meter accuracy for navigating harbors. It was then that a system of
differential corrections
was developed by the Coast Guard that enabled
them to effectively circumvent SA’s built-in errors.
These differential corrections are generated by fixed “reference stations”
and broadcast by marine radiobeacons over a relatively limited area—
usually a maximum broadcast radius of 250 miles—to Differential-
capable GPS (DGPS) receivers. The precise geographic location of the
reference station is used to calculate corrections based on the GPS data
received from the satellites, and the corrections are then broadcast to
DGPS receivers. The receivers then convert this data into extremely
precise position, heading and speed information. (Referred to as
selective
availability
GPS and DGPS

Rev. D 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Page 7
“beacons,” the transmitters are being situated at various locations along
the U.S. coastline and Great Lakes, most of which are former marine ra-
diobeacon sites.)
With DGPS, navigators are guaranteed position accuracy on the order of
2-5 meters
50% of the time, and to 10 meters 95% of the time (usually,
much better). Lat/lon positions displayed to thousandths of minutes
(roughly 6 feet) are common with DGPS. When using a radar or elec-
tronic plotter, DGPS corrections improve the steadiness of your dis-
played plot line dramatically.
In addition to accurate positioning information, DGPS provides critical
“integrity monitoring” of the received GPS signals, enabling the user to
be notified in seconds (as opposed to hours, with uncorrected GPS) that
an anomaly has been detected in a transmitted satellite signal. The integ-
rity monitor instructs the DGPS receiver not to use data from the satel-
lite in question.
Loran, on the other hand, can still outperform non-differential GPS—
when SA is in effect—in
repeatable accuracy
. Though susceptible to
weather and characterized by a relatively limited range (when compared
to GPS), it’s a dependable system familiar to thousands of boat owners.
Since the 1970’s, LORAN users have relied upon that system’s ability to
repeatedly get them back to a previously-saved location with extreme
accuracy. Fishermen 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 to within 50 feet
(or roughly 14 meters) of your previously-visited target. On the other
hand, at its very best, uncorrected GPS with SA enabled will get you to
within
300 feet
(100 meters) of your intended destination. Obviously,
uncorrected GPS—with variations of up to 300 feet in displayed posi-
tion—wouldn’t be much help in getting you through a narrow channel.
Since most loran chains were configured for optimum coastline naviga-
tion, it’s easy to see why loran’s
repeatable
accuracy has served harbor-
masters and fishermen well for the last 25 years.
loran

Page 8 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Rev. D
Loran, however, isn’t as proficient as GPS in
absolute accuracy
, or visit-
ing a spot for the first time. Since it transmits at a relatively low fre-
quency (100 kiloHertz—similar to that on your AM radio), your ability to
get an accurate position “fix” is directly related to: 1) your distance from
the loran transmitters, and 2) the weather between you and the trans-
mitters. It’s in these two areas that GPS consistently excels when it
comes to
absolute
accuracy.
Even with SA, GPS provides an
absolute
accuracy of around 300 feet
nearly everywhere in the world, under virtually any conditions. With a
“constellation” of satellites orbiting the earth and transmitting their po-
sition data on an extremely high frequency (1.575 GigaHertz, or 1.5
bil-
lion
cycles per second), GPS is impervious to weather and your location
on the surface of the earth. You can receive position fixes at any time,
anywhere, in any weather. This far surpasses the
absolute
accuracy that
is achievable from a good loran receiver in a strong signal coverage area,
in favorable weather conditions:usually 600 feet.
If you are accustomed to using your Northstar loran’s
repeatable
accu-
racy to return to within a boat length of a lobster trap or a buoy, time af-
ter time, you will not necessarily see this same performance with
uncorrected GPS—you could be as much as 600 feet from your expected
position. This will be especially apparent when using the 941X’s plotter
screen (without DGPS), where you may see your boat’s plotted position
appear to wander around within an area up to 600 feet in diameter (see
Figure 1 below).
You could be
anywhere within
the circle, 95% of
the time.
Position circle of 300-foot radius,
showing possible 600-foot error
between fixes.
300’
300’
ACTUAL
40°00.000 N
72°00.000 W
Figure 1—Max. Position Variances with Uncorrected GPS

Rev. D 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Page 9
If you need a higher level of accuracy than what basic GPS provides,
there are two choices available to you:
1. Use
Differential GPS
by installing a Northstar internal differential
beacon receiver (or use an externally-located Northstar differential
beacon receiver), or other source of differential corrections for your
941X. DGPS should provide better than 10-meter accuracy (repeat-
able and absolute) 95% of the time. See “Using GPS” on page 25 for
more information.
2. Interface your
loran receiver
to your 941X (provided the loran has
the appropriate NMEA 0183 format output capability). You will
then keep the “repeatable accuracy” of your loran, and add all of
the navigation features of the 941X, including the excellent world-
wide “absolute accuracy” of GPS. Refer to Table 2 on page 114 for
connector pin wiring guide.
The 941X is designed to be yoke- or flush-mounted on your boat. The
unit is waterproof and can be exposed directly to the weather. The GPS
antenna should be mounted fairly low on the vessel to minimize the ef-
fects of pitch and roll, and where it has a clear view of the entire sky. The
Beacon Receiver antenna (if installed) should be mounted fairly high,
like a loran antenna. Refer to “Mounting the 941X,” on page 100, for de-
tails.
The following functions are unique to the 941X; you may want to read
about them in detail before using them.
The 941X automatically converts GPS coordinates to loran TDs for those
who have lists of fishing spots and other waypoints recorded as TDs. This
feature is called Phantom Loran™. You can display your position as TDs
or enter waypoints as TDs. The accuracy to be expected from this conver-
sion is generally better than 500 to 1500 feet. You can also interface your
existing loran receiver to the 941X and then display and navigate with
getting more
accuracy
Mounting
Special
Functions
loran TDs

Page 10 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Rev. D
real-time loran TDs. These features greatly ease the transition from using
loran to using GPS. See page 30 for further details on using loran TDs.
The 941X’s plotter provides a picture of your position, and of what is
around you. Nearby waypoints, avoidance areas, and a lat/lon grid may
be displayed along with an image ofyour boat.
When you are using the plotter, the five menu keys below the display
screen allow you to perform the following functions:
1) restart the desired track line to run directly from your position to the
waypoint, “zeroing” the cross-track error display
2) change the options available for the plotter
3) center the image of the boat on the screen
4) zoom in to show more detail
5) zoom out to show more area
See page 22 for more information on using the plotter.
TideTrack displays a 24-hour tide graph for any of over 3,000 NOAA tide
stations covering the entire U.S. coast, including Alaska and Hawaii, as
well as much of the western Canadian coastline. Tides may be shown for
today or any other day you choose. See page 71 for more information on
using TideTrack.
The Liquid Crystal Display (LCD) and all controls are lighted for night-
time use. The display is easily readable under all conditions, from full
sunlight to total darkness. Anti-reflection treatment of the display and its
window eliminates over 90% of the reflection and glare. Important data
can be displayed using large numbers which can be seen from a distance.
To adjust the brightness, press the STAR key ( ) and use the BRIGHT
and DIM menu keys to set the desired illumination. Contrast is con-
trolled by the ARROW key to the left of the screen.
Use caution when cleaning the plastic window in front of the display
screen. Although it is resistant to scratches, it can be damaged if you
wipe dirt off with a dry cloth. Always use a damp cloth when wiping the
window. Use a small amount of window cleaner or alcohol to dissolve
plotter functions
TideTrack™
The Display
Screen
cleaning the
screen

Rev. D 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Page 11
any oil or grease on the screen. Whenever possible, avoid touching the
window with your fingers, as natural oils from your hand will temporar-
ily degrade the characteristics of the window and cause your fingerprints
to appear as bright reflections. These will disappear when the screen is
cleaned as described above.
The 941X contains two independent output ports for driving NMEA-
compatible devices, two input ports for accepting data from other NMEA
devices, and an auxiliary port reserved for future use. It also features an
RS-232 port for input or output of SC-104 DGPS corrections, and way-
point/route or software program loading from a PC. The 941X can be
interfaced to a wide variety of devices, including autopilots, plotters, ra-
dars, etc. Refer to “Interfacing the 941X,” beginning on page 112, for
more information.
CLEANING HINT
CLEANING HINTCLEANING HINT
CLEANING HINT
Pre-packaged moist towellettes (especially those containing a
small amount of alcohol) are excellent for cleaning the display
window. You might wish to keep a supply on hand to wipe off
fingerprints and other smudges.
Interfacing
Capability

Page 12 1 — Introduction
1 — Introduction1 — Introduction
1 — Introduction Rev. D