Do you believe the horizontal horizon line is a line?

Oh crap, it's the "curves aren't lines" thing again. This is just more equivocal pain-pong.

Continually running around in a circle, thinking it is somehow a line, is perpetual stupidity.

Indeed. We are talking to two people who, looking out at the ocean, are so mentally disconnected that they genuinely believe they perceive there to be some "curve" in the COMPLETELY HORIZONTAL LINE of the HORIZON.

1. Who is doing that?
2. Please quote EXACTLY where or
3. Retract or
4. Be shown to be either
  1. A liar
  2. Physically incapable of further response, which will be belied with any other subsequent post.

More for the flat-tards to ignore...

Understanding radar horizons and pulses 2/27/2017 By John Barry Technical marine electronics dealer and NMEA instructor John Barry wrote the article below for Marine Electronics Journal.  It gets a bit techy toward the end but we left the info in for those readers who want more detail. Radar Horizon A radar is basically a line-of-sight device. I say basically because a phenomenon called “knife edge refraction” adds about 15% to the range of a radar compared to sight, allowing it to see just a little bit over the visual horizon. This is caused by the difference in the way light vs radar waves are acted on by the atmosphere.  For this reason, we refer to the maximum range that a radar wave can reflect from a surface target as the radar horizon. There is much misunderstanding around this subject, so let me lay it to rest right here. The formula for radar horizon is Radar Horizon=1.23 x Square Root of Height. So, a radar 25 feet above the water has a radar horizon of 6.15 nm (5 x 1.23). That is correct—a radar 9 feet high has a horizon of 3.69 miles (3 x 1.23). The range of a radar cannot exceed these physical limitations. The radar horizon refers only to a low object, theoretically zero feet tall. In practice, our targets have height. We sum the square roots of the heights then multiply by 1.23 to get the maximum detectable range, so: square root 625 = 25, square root 25 = 5, (5 + 25) x 1.23 = 36.9 nm in the example above. As you can see in the drawing, some targets, like land, are very tall. Note in the example that the vessel detects a return from land at 36 miles but the vessel is only about 25 miles off shore. The radar does not mark the beach, it marks the hills 10 miles further inland than the beach.   Pulse Widths As most of us know, radar is short for RAdio Detection And Ranging. A radar transmits a pulse of microwave energy, then waits for the echo. Based on the time for the return to arrive, distance can be determined. Direction is determined by rotating the antenna to face the target. Pulsed radar uses packets of microwave energy produced as the transmitter is turned on and off very quickly. The duration of this packet of energy, or pulse, is called the Pulse Width (PW). This is the time the radar spends transmitting. Since it takes time for the pulse to travel to a target and back, we must listen for returns most of the time and transmit the radar only for a short time, the time of the pulse width. It is desirable to use the maximum pulse width possible in order to get the maximum return possible. A wider pulse width means more energy in the “packet” and hence more energy on the target and more coming back in the “echo.”   Pulse Repetition Frequencies The pulses produced by a radar are repeated over and over. We transmit for a short time, listen a long time, then rinse and repeat. Typically a radar transmits and receives about 1,000 times per revolution of the antenna. The number of times we repeat the pulse per second is called the Pulse Repetition Rate (PRR), or Pulse Repetition Frequency (PRF). How long we transmit (PW), how often (PRF) and how long we listen for (Range) is all controlled by varying the Pulse Width and the Pulse Repetition Frequency. Radar manufacturers design their units to use the appropriate PW and PRF on the appropriate ranges. Pulsed radar ranges are selectable from the max rated range, sometimes 96 nm, down to the 1/4 or 1/8 nm range. Since radar waves travel approximately the speed of light, they travel 1 nm in 6 microseconds. When a radar produces a pulse, it must stop transmitting before listening for returns. It also must finish listening for returns before repeating the transmit pulse. Because of these two factors (no simultaneous transmit and receive), the speed of wave propagation through air and the RPM of the radar antenna become major factors. In order to accomplish short-range radar operation, we must use a short PW since we must hurry up and listen for the returns that come back quickly from a close target. Since the time is short for short-range targets, we can repeat the pulse often (higher PRF). This allows for faster updates and better target detection. We can also spin the antenna faster, at 24, 36 or 48 RPM. Faster rotation means even faster updates, a useful feature for tracking high-speed targets. For longer range targets, we use a longer PW to throw more energy at the target. When we have to wait for a long time for a return from a distant target, we can’t repeat the pulse as often (lower PRF).  We also cannot turn the antenna at 36 or 48 RPM, so the traditional 24 RPM rotation speed is used on long ranges. Higher RPM on longer ranges means the antenna has turned away by the time the reflection comes back. Some radars allow the operator or installer to vary the PW and PRR of their radar sets. Do not change these unless you understand exactly why. Understanding PRFs and PWs is part of passing the Federal Communications Commission General Radiotelephone Operators License (FCC GROL) radar test and becoming a NMEA Certified Marine Electronics Technician. First. We need to know how these factors affect ranges. Also understand that a longer pulse width means more stress on the power supply and magnetron. Interestingly, a failing magnetron may show weak targets on short ranges first if the mag does not trigger quick enough. Typically, weak long-range targets are the first symptom of a failing magnetron due to decreased power output. Transmitters and maggies are a story for another day. In the meantime, keep your PWs and PRFs straight and watch what you are doing, understand it, learn it.   A note on operation Short ranges on radar can be useful for docking or close quarter navigation. When on the 1/8 nm range, the distance from the center of the screen to the top is about 650 feet. A vessel traveling 40 knots is going about 60 feet per second, so two vessels going 40 knots close at 120 feet per second. This means that the screen is crossed in five seconds by these example vessels approaching head on. The presence of high-speed craft is a big reason for 48 RPM radar and also a good reason to stay above the 1/4 mile range so you have time to do something about a collision situation. The radar is the primary safety device on the boat, so make sure it is installed properly, working optimally and that the operator understands its use. I recommend to my customers that they practice using their radar in clear conditions so that when it is needed, the operation is intuitive. The NMEA teaches an in-depth radar installation class as part of the newly revised AMEI— Advanced Marine Electronics Installer—training.   About the author John Barry owns Technical Marine Support, Inc. in Pleasant Prairie, WI. He is a NMEA Certified Marine Electronics Technician and teaches several NMEA technical courses, including Marine Electronics Installer and NMEA 2000 Network.

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