NASA Marine CLIPPER User manual

CLIPPER
GPS
REPEATER
Speed over ground
Distance to Waypoint Bearing
Track
3D
CLIPPER GPS
LIGHT DEST. STEER POSN.
DESIGNED AND
MANUFACTURED
IN ENGLAND
RoHS
2002/95/EC

CONTENTS PAGE
INTRODUCTION
INSTALLING THE DISPLAY
INSTALLING DIAGRAMS
GETTING OPERATIONAL
USING THE REPEATER
USING THE ROADWAY DISPLAY
ROADWAY DISPLAYS
TECHNICAL INFORMATION
TROUBLE SHOOTING
1
1
2-3
2
4
5
6
7
Page8 &Inside back cover

INTRODUCTION
The Clipper GPS Repeater is supplied with 10 metres of cable, a 3
way terminal block, and a 12 Volt power cable. The unit will repeat
the data sent by any GPS repeater set up to send NMEA 0183
output sentances RMB and RMC at 4800 baud.
INSTALLING THE DISPLAY
Select a convenient position for the display on a panel or bulk-
head. The site must be flat and the cavity behind the panel must
remain dry at all times. (The cable entry is deliberately not sealed to
ensure adequate ventilation. This prevents misting of the display).
Cut a hole in the panel 67mm high and 87mm wide. Bring the
wiring through the hole in the panel and pass the 10 metre cable
through the hole.
Unscrew and remove the two wing nuts from the rear of the
instrument and remove the stainless steel clamping bracket. Fit the
“O” ring seal into the groove in the panel mounting face of the
instrument. Ensure that it is correctly lying in its groove before fitting
the instrument to the panel, which provides the watertight seal for
the display.
Fit the instrument into the panel, fit the stainless clamp over the
studs, fit and tighten the two wing nuts finger tight only.
It is important that the O-ring rubber seal makes good contact with
the panel to prevent water getting behind the unit and entering the
cavity behind the panel.
It is good practice to run the cables vertically downwards from the
unit, even if they later have to rise to connect to the vessel's
supplies. Doing so prevents any water that might get onto the
cables from running back along the cables and into the unit.
1

GPS
RECEIVER
Figure 1
2
NMEA OUTPUT or
NMEA OUTPUT (+ve ) wire
Negative Supply Wire
If it exist, its usally labelled NMEA OUTPUT (-ve)
or NMEA OUTPUT (REF)
If not, then the reference is internally connected to ground,
and can be ingnored
Uncoil the cable and install it on a convenient run to the GPS receiver
position.
Refer to Figures 1 and 2. to connect the GPS receiver to the GPS and
vessels supply.
GETTING OPERATIONAL
Switch on the GPS receiver. Refer to the manufacturer's handbook, and
set up the unit to send NMEA version 2.0 (or later version) at 4800 Baud.
When the GPS Repeater is powered on, the words Clipper GPS appear
momentarily on the screen. Note that the words are shown in a mixture
of Upper case (capitals) and lower case characters. This is because the
numerical display is also used to display text.

3
DEST. POSN.STEERLIGHT
+ve -ve
12 Volt SUPPLY
Figure 2
Blue
Silver/Black
Red
The International Seven-bar Substitution Character Set
(ISBSCS, usually shortened to ISCS) is used to represent the Upper-case
alpha-numeric characters used by most GPS receivers, as shown below.
A B C D E F G H I J K L M N O P Q R
S T U V W X Y Z 0 1 2 3 4 5 6 7 8 9 -

4
On some GPS receivers, no NMEA output is sent until lock onto the
satellites is achieved. If so, the Repeater displays the message “No
GPS Signal” as a warning. When the GPS Receiver has acquired
lock, the current position (Latitude and Longitude) will be displayed
on the Repeater.
Regardless of the settings on the GPS Receiver, the repeater always
displays distances in Nautical miles, speeds in knots, and all
bearings in magnetic. Latitude and Longitude is shown in degrees,
minutes and tenths, hundredths and thousnds of a minute.
USING THE REPEATER
Press POSN. at any time, and the repeater will display the current
position (Lat and Long) after a brief pause while it collects the fresh
NMEA data from the receiver. Unless a waypoint is selected on the
receiver, this is usually all the data available to the repeater.
Select a waypoint ( a destination) on the GPS receiver and press
STEER. The repeater will show the Speed over the ground (SOG)
screen. This screen shows the road, the speed over the ground (the
course made good), track, and distance and bearing to the
waypoint.
A second press of STEER shows the cross-track error (CTE) screen.
This replaces the speed over ground with the Cross-track error, and
leaves the other values as before. Pressing STEER alternates
between the CTE and SOG screens.
Press DEST. to display the name of the next waypoint (which has
been entered into the GPS receiver) and the direction to steer to
reach it. If the destination is within 30º of astern, “Astern” is
displayed, with the roadway showing the best turn direction to
regain the desired waypoint.
Press LIGHT to switch the backlight on at low level, and again to
switch the backlight to full brightness. Another press switches the
backlight off again.

5
USING THE ROADWAY DISPLAY
The roadway display is available on the DEST and STEER screens
(CTE and COG).
Steering guidance is represented on the roadway display. The
display indicates the direction to steer to reach the destination
waypoint from the present position. It does not indicate cross-track
error from the track between the departure and destination
waypoints stored in the GPS receiver.
If the cross-track (CTE) is being displayed, the cross-track error
includes a Left (L) or Right (r) indication, which indicates the
direction to steer to rejoin the desired track between departure and
destination waypoints.
The roadway display always shows the best direction to turn, even
if the vessel is moving away from the destination waypoint (and see
above). If the vessel is going away from the destination, this is
shown by the large difference
between the bearing to waypoint (destination) and the Track.
The roadway displays are shown overleaf, for all track and bearing
differences.

6
“Ahead”
Track within 3º of bearing to destination
Steer left Steer right
(Track > 3º off bearing to destination)
Steer left Steer right
(Track > 6º off bearing to destination)
Steer left Steer right
(Track > 9º off bearing to destination)
Steer left Steer right
(Track > 12º off bearing to destination)
Steer left Steer right
(Track > 15º off bearing to destination)

7
TECHNICAL INFORMATION
The GPS Repeater offers full functionality only when the GPS receiver
is set up to send NMEA 2.0 (or later) messages at 4800 baud. NMEA
Message types RMB, RMC, and GSA are required to fulfil all the
repeater's functions.
The repeater always shows the status of the signals it is getting from
the GPS receiver. If no NMEA data are being received, a No GPS
Signal message is displayed.
Some GPS receivers send NMEA data before full satellite acquisition is
achieved, but others wait until full acquisition is achieved before
sending any data over the NMEA connection. If position (POSN.) is
requested, and none is available from the GPS, No GPS POSN. is
displayed. If no Cross-track Error or Speed over Ground information is
available, appropriate messages are shown.
The Repeater always displays magnetic bearings, using the magnetic
offset sent by the GPS receiver. If true bearings are wanted on the
Repeater, it is necessary to set the GPS Receiver to Magnetic, and set
the magnetic deviation manually to zero.
The cable to the Repeater has two wires, Red and Blue, and an outer
screen. The screen is negative, and the red wire is connected to +12
Volts. The Blue wire carries the NMEA data from the GPS Receiver. The
cable can be shortened or extended up to 20 metres if desired.
Supply voltage: 8-16Volts D.C.
Current 3 mA (backlight Off)

8
TROUBLE SHOOTING
PROBLEM LIKELY CAUSE REMEDY
Repeater is
totally dead
No power to
Repeater
Check 12V supply,
fuse, and connections
between 10m cable
and GPS.
Check cable for
damage.
Repeater
reports “NO
GPS Signal”
Not getting NMEA
from the GPS
Receiver
Check GPS Receiver is
set up to send NMEA
version 2.0 (or higher)
at 4800 Baud.
Repeater
reports “NO
GPS Signal”
Not getting NMEA
from the GPS
Receiver
Check GPS Receiver
is on and has acquired
lock. Check wiring
connections.
Repeater
shows “No
GPS DEST”
or “No GPS
SOG” or “No
GPS CTE”
No Waypoint
selected on GPS
Receiver
Select waypoint
Repeater
shows “No
GPS POSN
Receiver still
acquiring position
Wait for acquisition
Information
on Repeater
appears
different to
GPS Receiver
The Receiver
has not updated
its NMEA output
Wait for update