I am afraid you all are confusing bearing resolution with bearing accuracy. These are two different things. A wider horizontal angle will bring resolution (I call it target discrimination) down so that two targets that are close together will only show one echo on the screen
However, for bearing accuracy, the width of the beam is not a factor. The factor that determines bearing accuracy is the size of the "steps" that the scanner makes while turning. A radar with a 5 degree horizontal opening angle doesn't make 5 degree "steps"... it makes multiple "steps" per degree. Even the JRC 1000 is listed as within 1 degree accurate on bearing.
If you add a compass
for true bearings (and North up display if you wish), the accuracy of that compass is a factor too. Inaccurate installation
or lack of calibration is not a factor because it must be installed right and calibrated. You can f&*k up any device by installing it wrong. Operator error is not a factor because you should operate it right. You can f&*k up the accuracy of any device by using it wrong.
A ships radar is indeed much more accurate on bearing than the radars for yachts. Here are some examples: Radar Basics - Accuracy of Measurement
As you can see, we're talking a fraction of a degree there and the MSSR-2000 is accurate to within 5/100 of a degree.
Also, stating that a 4kW dome is not representative for yachts (like it is bigger/better) is not right. We're talking about a small dome, not even an open array scanner. I think it is more common than smaller domes, at least it is where I am.
A radar set that doesn't have EBL (Electronic Bearing Line) is just silly... they all have that, even the JRC1000 does have it, as they all have VRM's (Variable Range Markers). You don't have to estimate the bearing on a radar screen
, you use EBL.
A radar set without a heading sensor (heading up display) is actually more accurate for a radar bearing than one with a compass, because the error of the compass is left out. The problem is that the bearing is relative to the boat's heading, so for plotting you have to calculate the true bearing and that is when you add the accuracy of the compass used to the mix again. But for purposes of collision
avoidance you don't need a true bearing so that a target in front of your bow really is in front of your bow and you must change course to avoid collision
The image painted by the radar on it's screen is NOT a virtual reality. If you think that, you either don't know what virtual reality is or you don't understand what radar is. Targets on your radar screen are real things that you look at with radar vision, just as you can see them with normal vision, or IR vision. Is the image of a FLIR unit virtual reality? How about what you see when you use binoculars? or how about the sea-bed on you fish
finder? None of those are virtual reality.
GPS time is the most accurate clock you will have on your boat. It is more accurate than your "atomic clock synchronized" time piece or the time signal on SSB
. Every GPS satellite
has an atomic clock aboard and the GPS uses up to 12 (many more soon) of those satellites, plus WAAS or DGPS correction methods to make it more accurate. The time you see is compensated for the distance between you and those atomic clocks. Your SSB
time signal is not compensated at all because your transceiver doesn't know where you are and the distance and signal path between the transmitter and your radio
. Same for those atomic clock synchronized time pieces. Also, those use long wave radio
transmissions that introduce much more errors that the UHF space to surface transmissions from GPS satellites.
Last but not least we get to the accuracy of GPS. True, it is based on an computer model of the shape of the globe. But what you fail to realize is that so is your chart. When your chart datum is WGS-84 and your GPS is set to WGS-84, the error of that model is compensated automatically. This is really basic navigation knowledge people, come on!