Integrating Radar with Computer Charting
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FOG CAN BE QUITE COMMON IN THE SUMMER HERE IN
the Puget Sound, often in thick patches in
the channels between the many islands
through which we cruise. And the fog can
be quite dense, although often the layer is
only 20 feet thick. It’s not uncommon to see one
of the large Washington State ferries plying the
waters in the San Juan Islands, its bridge showing
above the fog bank but with lower decks
completely hidden.
Having radar to pick up these fast-moving craft
is very important.Another reason is that this part
of the world is an active fishing region, and one
never knows when a cruising trawler will run
into an entire fishing fleet. Finally, picking your
way through narrow channels bounded by large,
pointy rocks in a thick fog is fundamentally not
fun.
So for all these reasons, radar is a vital piece of
navigation equipment and helps make for a less
stressful cruise.We frequently see a ferry running
the passages between the islands, closely
followed by a group of small boats that don’t
have radar.These boaters can see the ferry a few
yards ahead in the fog, so they follow it in a
convoy, like ducklings in a row.
Our boat, Loon Song, has a lovely Furuno 1900
CRT-based radar unit installed on the lower helm.
I always power it up when cruising, and I like to
see the 40-inch open array antenna slowly
rotating on top of the boat’s electronics arch.
Unfortunately, as we generally operate the boat
from the enclosed flying bridge, we miss the
utility of a radar display at this upper helm. So
until recently, running into a fog bank meant
moving down to the lower helm and peering
through the windows and watching both the
radar screen and chart plotter.
Electronics Update
Loon Song was commissioned in 1989, and
much of her electronics are feeling their age,
even though all of them functioned properly
when we bought her in late 1997. But after
hitting a submerged ledge on our very first yacht
club outing on Easter 1998—ruining a set of
props, rudders, and shafts—I decided to get a
more detailed chart plotter and a forwardlooking
sonar installed.These projects lead to the
installation of a fixed computer and dual displays
on the lower and upper bridge. (See sidebar.)
After a year of using the large LCD computer
display on the upper helm with Nobeltec’s Visual
Navigation Suite, I realized that the next step
would be to add a radar display on the upper
helm as well. So with that in mind, I puzzled over
several of the issues this brought to mind:Where
to place yet another display? Could I use the existing radar unit, and simply add another
display? How difficult would the installation be?
While studying these questions and all
potential solutions, I received a letter from
Nobeltec informing me that they were offering a
special deal on the newly announced
RADARpc™, a joint development between
Nobeltec and SI-TEX.
The RADARpc system consists of an enclosed
radar antenna and related electronics, as well as
an interface to an onboard computer where the
image processing is done and the computer
display replaces the traditional dedicated radar
display.
As I already had a ship’s computer and lovely
dual 15-inch LCD displays at each stations this
solved my first issue. The LCD display on the
upper helm is bright enough to be visible in
normal daylight, and I use it at all times with
Nobeltec’s Visual Navigation Suite (VNS)
software, which shows Loon Song’s position on
raster NOAA charts.
I also knew that the computer had enough
processing cycles to handle additional functions,
as Microsoft Windows’ System Performance
Monitor showed that VNS only consumes five
percent of the processing power of the 333-MHz
computer. So I decided RADARpc would become
the ship’s main radar unit, and the lower helm’s
Furuno would become its backup. While the
Furuno has a much greater range, it’s difficult to
get more than 10 miles from land within Puget
Sound, and most boating is within a couple of
miles of shore.
This solved my second issue.
The installation question was resolved when I
visited the capable crew of Seattle Yacht Service
in Seattle. Loon Song’s existing electronics arch
was already pretty full with dual VHF antennas,
two different GPS antenna pods,the large Furuno
open array antenna, a loudhailer speaker, and a
satellite TV antenna.
Their electronics expert suggested that we
fabricate a subarch to hold the RADARpc dome
above the Furuno antenna with enough vertical
clearance to ensure that the two radar beams
would not interfere with each other or the other
existing electronic arrays.
Unfortunately, this added a week and $800 to
the project.
Loon Song’s New Eyes
Once installed on the new electronics subarch,
the RADARpc enclosure looks good and works
well.We routed the combined signal output and
power cable into the main electronic arch and
down to a bulkhead inside the upper helm.This
task was fairly easy to accomplish, as I’d asked technicians to leave a pull cord in the raceway
the last time work had been done on the
electronics arch to install the DGPS antenna pod
and the satellite TV dish.
SI-TEX’s RADARpc outputs its signal over an
RS-422 interface cable mated to the electronics
dome. However, few computers have a native
RS-422 interface, so SI-TEX provides three
interface options for computers: PCI card for
internal mounting in the computer, a USB port
for most new laptops and desktop computers,
and a PC Card (PCMCIA) attachment for laptop
computers.
I decided to use the USB interface because I
didn’t want to have to open up the case of the
computer. The PC Card interface would be
suitable for older laptops that don’t have a USB
port. The USB option requires a small
conversion box, which we located inside the
upper helm, running the USB cable down the
nearby cable raceway to the lower helm. Having
the USB interface available at the upper helm
means that I can use my laptop as a backup unit
if the normal ship’s computer fails. I do like
redundant systems. Once the USB cable was
routed to the lower helm, the final connection
step was to insert the connector into the front
panel of the computer. Connection
accomplished!
Software installation was actually quite easy.
The package from SI-TEX included a CD-ROM
containing a copy of VNS version 5, along with
the radar interface software. Because I already
had the most recent release of VNS installed, the
software installation was fast, and none of my
charts or routes were lost.
It might be useful to mention the skill levels
of the installation team. Larry, the expert from
Seattle Yacht Service, is quite experienced in installing marine electronics and computers. I
have been in the PC and networking business
for 35 years and have owned PCs since the first
IBM PC came out 20 years ago. So I was
confident that the box of electronics sitting
before us would an easy morning’s work.
Wrong.
Getting The Bugs Out
We powered up the PC, started VNS, flipped
the circuit breaker powering both radars, and hit
the button to start the RADARpc in transmit
mode. Nothing. Nobeltec’s Radar Wizard
couldn’t see the radar.
We checked the connections, but all was fine,
and DC power was at the radar dome and the
antenna was rotating.
Back to the documentation. Oops, we needed
to install a device driver for the RS-422 to USB
converter box. Here’s the floppy, stick it into the
computer and run the installation program.
Done. Let’s try the system again. Shut everything
down (a very good rule) and start from scratch.
Same result—can’t see the radar. Again, check
the solder connections (the RS-422 cable
requires one of two different connectors,
depending on type of interface) and the power.
All good. Check software and test the new
device driver, all good. Time to phone SI-TEX.
The technical support folks answered on the
first ring, and we started through problem
determination. Larry and I had already asked the
obvious questions, so the SI-TEX technician
suggested that Larry open the radome and check
some of the wiring, as a few of the units had left
the factory with poor connections, a problem
they have since resolved. Larry climbed up to
the electronics arch and opened the radome
(something normally not done by customers)
and tested voltages. All Okay.
Back to the computer. The Radar Wizard still
couldn’t see the radar. Lots of head scratching,
rereading the documentation (pretty good stuff,
we thought), and retesting.
Lunchtime arrived, and it was off to Mike’s
Chili Parlor near the 15th Avenue Bridge in
Ballard for a chili burger. Maybe a full stomach
would help resolve the problem.
Pesky Dip Switches…What Dip Switches!?!
Back on Loon Song, I re-read the installation
guide for the umpteenth time. “Larry, did you set
the dip switches on the USB interface box this
way?” I asked, pointing to the diagram.
“No switches on the box,” replied Larry.
“Are you sure? Because the instructions say to
set the switches this way,” I repeated.
Larry insisted that there were no dip switches
on the conversion unit. We clambered up to the flying bridge and crawled into the upper helm.
Nope, the box had no dip switches.
“Could it be a different conversion box?” a
muffled cry came from inside the helm.
Indeed, the documentation from SI-TEX
described a USB conversion unit made by
Edgeport, while the box that shipped with our
unit was made by Quatech. A phone call to SITEX
confirmed the switch. SI-TEX was shipping
units with a new conversion unit, and
apparently the documentation we had was not
yet updated. The Quatech box has different pinouts
for the connector to the RS-422 cable (and
does not use dip switches). The reason for the
change was the new unit had the same pin-outs
for the RS-422 connector as for PCI and PC Card
interfaces.
Progress!
Larry resoldered the connector to match the
Quatech box, and I checked the USB driver. It
was for the correct unit. Then we powered up
the system and—wow! A radar image showed
up overlaid on the NOAA chart. It worked like
a charm. A few tweaks here and there to get
familiar with the Nobeltec software tools and we
were ready to head out for a sea trial.
I had also installed a new interface box for the
autopilot to connect to the DGPS, and to the
ship’s computer and VNS software. I wanted to
test the new autopilot function as well.
I pulled away from the dock, watching my
new radar display overlaid on the charts, and
was quite pleased with this new level of
integration of navigation tools. Heading at a
leisurely five knots toward Lake Union, I
compared the RADARpc image on the computer
screen with the Furuno radar image next to it—
when all of a sudden the computer image went
blank, replaced with a message saying there was no signal found from the radar.
Good thing this was a sea trial on a clear day.
This was the same situation we had
experienced before, when the computer did not
recognize the radar input. I knew we got the
correct pin-outs soldered on the connector, and
couldn’t determine the culprit.
The rest of our sea trial continued down hill,
as we found problems with the autopilot and
the new flux-gate compass, so we headed back
to the dock, cold and temporarily defeated.
Thinking that the USB interface unit had
failed, Larry replaced it with another one from a
second RADARpc unit he was installing the next
week. It worked, so we set out again. Then
failure again after five minutes. Two units
shouldn’t fail out of the box that way. What was
wrong?
What was the problem here? Dirty electrical
power is more common on a boat than most
think. While the radar unit ran fine dockside
with shorepower, it failed running off the
inverter system.
Yes, the same 12VDC supplied the USB
interface unit, but noise was introduced into the
DC lines when the inverter was producing AC
power for the computer and its displays.
Installing a couple of ferrite filter coils on the
USB cable at the converter box removed the
noise, and the USB interface worked like a
charm.
The lesson I learned is that environmental
conditions are not the same while tied up at a
dock as when under way. Also, it is important to
consider the big picture when debugging
electronic equipment, as the problem may not
be with the equipment itself, but its operating
environment.
Work In Progress, And Gaining
A couple of weeks later when we took Loon Song back home to Anacortes. It was a clear, but
chilly day as we made the 56-mile passage, and
I drove from the upper helm with the Nobeltec
VNS software running the autopilot and with
RADARpc images overlaid on the NOAA charts.
I used the trip to become familiar with the
controls of the software and with adjusting the
gain and colors of the radar display.
It was nice to see the ferry leaving Clinton
show up on the screen. Adjustments to gain and
alignment are easily accomplished from dropdown
menus.
I found green for a mid-strength echo return
is a bit too bright on my computer, as it tends to
hide the details of the chart under the radar
overlay. I changed it to a lighter and more
transparent color.
I also alternated between side-by-side radar and
chart images and decided I like the superimposed
image the best, as more chart area is displayed.
One feature that should be changed by
Nobeltec is to allow the displays for gain and
STC to be moved, because they tend to sit over
the current position of the boat when using the
Look Ahead feature of the Autoscroll function.
I normally run with a Course Up display
orientation, and with the Look Ahead feature to
display as much of the route in front as
possible. This means that the current boat
position is always near the bottom of the
screen.
However, this also means the radar view to
the rear of the boat is somewhat truncated, and
I can’t see boats coming up from astern.
I will probably use the Follow Boat setting of
Autoscroll when in fog, so as to display as much
of the space around me as possible.
The Future Is Now
I feel that RADARpc has made my boating
activities more secure, and I no longer dread fog
as I did before. My anxiety is greatly reduced.
We now enjoy Loon Song over a wider range
of conditions without stress, and I can focus
proper attention on running the boat safely into
the sunset. Even if that includes fog or rain.
It’s the only way to go.
Reprinted with permission. Copyright 2001 © Dominion Enterprises (888.487.2953) www.passagemaker.com
You are reading the text-only copy of this article. To access the article as it appeared in PassageMaker Magazine, please log in to purchase and download the PDF version of this article.