ARPA let's you "acquire" a target. It all sounds very military, but it's a really critical feature for navigation and collision avoidance. When you acquire a target, the radar tracks that blip on the screen, and calculates it's course and speed based on it's observed movement. It's all basic trigonometry, and a great example of how that stuff is actually useful. As one of my kid's teachers used to say, "math is everywhere".
So in the middle of the night, or in the depth of fog, you see a blip on the radar. Rather than watching the blip and trying to assess where that boat is going and what it's doing, you can acquire the target on your radar. Within a minute or so, the radar will show a vector (see, math is everywhere) indicating the target's direction and speed. Now, rather than guessing, you can see exactly where that boat is going, and how fast they are moving. This is hugely valuable, and probably hard to appreciate if you haven't tried to navigate in the fog. We've made a couple of trips from Gloucester to NYC, a trip of about 300 miles through some of the busiest waterways on the east coast, and never seen land or another boat the whole way. That wouldn't be possible without ARPA, or at least the stress level would prevent me from doing it.
The killer problem with Simrad is that their ARPA function is fundamentally broken in the current product line. We first became aware of this when we nearly got run down by a boat off the Columbia River. After that, I really started looking at this closely. The problem is that:
1) The ARPA vector does not accurately represent the boat's movement
2) The vector's direction swings around and is unstable
3) The vector's length (boat speed) is also unstable and varies widely.
The attached video shows this clearly. We are looking at a tug and barge. The tug has AIS which is a radio-based report from a boat telling you it's actual speed and course. There is no ambiguity, and no room for error. It is telling you exactly what the ship is doing. The AIS target is represented by a triangle with a line showing the course and speed of the tug. I have then created a ARPA target of the barge behind the tug, represented by a circle and arrow showing it's course and speed. The tug and tow are of course moving at the same speed and in the same direction, but the video would suggest differently. Referencing the points above, we see:
1) The ARPA course and AIS course differ significantly. They should be the same, or very close.
2) You can see that the ARPA vector swings around rather than maintaining a steady course.
3) You can see that the ARPA vector changes length by quite a bit. It should be a consistent length. representing a steady speed.
The result is ARPA that is simply not usable. I've worked through a wide range of tests and experiments with Navico support and engineering, and the installation has been scrutinized every way to Sunday and passed with flying colors. Engineering finally reproduced what I have been seeing and agreed there was a problem they needed to fix. This impacts both my radars (4G and 10kw open array), and based on reports from other Simrad owners, appears to be a long standing problem that has gone unnoticed until now.
As part of testing, one thing Navico asked me to do was to acquire the same target multiple times. They wanted to see whether there was any difference between the different targets. The next video shows this. I acquired the target three times, and you can see that two of the vectors are mostly in lock step with each other, but the other is pointing off in a different direction. And all three wander around.
Over on the right side of the screen you see a bunch of data boxes, include 3-4 larger ones showing various AIS targets. My understanding is that these are supposed to be the closest target. But you can see that there is no data in the data boxes. You see a ships name in one case, and just the MMSI (ship's number) in the others, but there is no course or speed info, and no computed CPA (closest point of approach), or TCPA (time to closest point of approach). If I look up these ships on Coastal Explorer (it also receives and displays the AIS data), all the info is there just as it should be. So the receiver is working and the data is available, but the radar is not displaying it properly. The targets plot correctly on the screen, but the data boxes are not filled in, and the CPA and TCPA is only occasionally calculated.
|Missing AIS info|
The radar incorrectly reports the operational hours on the Magnetron. A Magnetron is the part of the radar that generates the ping used to find targets. It's the Flux-Capacitor for a radar, and it has a limited life span. They are good for a few thousand hours, but when their time comes they need to be replaced. So all radars have a built-in hour meter to keep track of this.
The Simrad 10kw radar reports a seemingly random number of operational hours. The first time I looked, it reported 26,000 hours and I thought I had been sold a used radar. But the next time it reported a very small number. Simrad confirmed it's reporting garbage info. I don't know how to maintain a radar under such circumstances. I guess I need to buy an egg timer.
Simrad advertises a feature whereby you can tell the open array what angle you want it to park at. Most radars just stop where they stop, and this little feature was really interesting to me since it allows the radar to be parked where it doesn't shade my solar panels. But despite numerous attempts to park the array in a predictable manner, I called Simrad tech support. They told me that the feature didn't work. Worse yet, they know it's not possible for it to ever work. The radar has no brake, so they have no way to control where it stops. WTF? Talk about false advertizing. Wow.
This one is related to the park angle that doesn't work and can never work, so it's kinda moot, but it's reflective of the overall disregard for product testing before releasing it for sale. You can go into the radar menus on the NSO and program in the angle where you want to array to park. But when you turn the radar off, it forgets the angle that you programmed in. So you need to reprogram it very time you shut down the radar.
Problem # 6:
This is another ARPA problem. If you lock onto a target, then shut off the autopilot, the ARPA vector swerves off about 90 deg from the actual course of the target. These two systems should have nothing to do with each other. Why turning off the AP impacts ARPA is beyond me, but it does. A friend tried the same experiment on his Simrad equipped boat and got the same results.