Si-tex SP-70 - The Navigation Interface; Cross Track Error

The Navigation Interface
Your SI-TEX Autopilot will receive information
sent to it from a navigation device (such as a
LORAN, plotter or GPS) in NMEA 0183
format.
See page 41 for navigation input connection
instructions.
Using information from a compass and the
navigation device, the Autopilot will steer your
vessel along a course line to a waypoint. The
Autopilot will also steer your vessel through a
series of way points which the navigation
device has grouped together as a route.
The Autopilot cannot steer by the
information from the navigation device
alone.
Cross Track Error
Cross track error is a measure of the distance
your boat has fallen away from the course
line.
Cross track error is measured as the length
of a line drawn from the course line to your
position at right angles to the course line.
Cross track error also has a left or right hand
direction. For example: The boat can be one
half a mile to the left of the course line.
Manufacturers have defined the direction of
the cross track in different ways. There is no
agreement on whether a left hand cross track
error means that the boat is to the left of the
course line or the course line is to the left of
the boat.
Because of this, the SI-TEX Autopilot lets you
change the way it interprets the direction of
cross track error. In N
AV MODE, press the
Flush Key. The display will show either [---‘n]
(normal) or [---r] (reversed). Use the Green
Key to change the setting.
Your cross track error direction is correct if
the Autopilot is following the course line.
If the Autopilot is steering
away from the course line
while the Navigation
Interface is on, then the cross
track error direction may be incorrect.
Change the cross track error sense. If the
Autopilot begins steering towards the course
line, you have solved the problem.
NMEA 0183
The SP-70 AND SP-80 receives information
from LORAN, plotters, and GPS in the
National Marine Electronics Association 0183
language. A list of the usable data sentences
is as follows:
1.
RMB + RMC
2.
RMB + RMA
3. APB
4. APA
5. XTE + BOD
6.
XTE + HSC
7.
XTE + WBD
8. VBW
9. VHW
10. VT
G
Your SI-TEX SP-70 and SP-80 Autopilot
conforms to the standards of the NMEA 0183
language.