High resolution March issue article here By Steve Katz Recently I visited a 68 sportfish. The vessel had received many helm upgrades. The control station was a beautiful helm with four large flush-mounted glass style monitors. Upon powering on the system, I witnessed a modern GPS chart plotter in high definition. In contrast, I also found a blurry radar image from a system introduced over 10-years ago that had been adapted (not well) to work with the new screens. Since it appeared that cost was not an issue, I asked how this happened. The captain explained that the previous captain was familiar with the old radar and knew how to use it. He therefore demanded it remain during the electronics upgrade. It seems the prior captain didnt want to learn a new radar system! There are many captains and owners who prefer to keep using the hardware they know. That said, the advantages to using modern electronics are worth the effort to take the time to learn! Radar Basics: Applications Let review why we use marine radar:
- Collision avoidance is the number one feature of marine radar. An educated radar user can use the displayed radar image to avoid a collision with land, other fixed objects and other vessels at sea. This use of radar is not just for nighttime use, it can be used anytime and can help locate and identify targets.
- Regulatory compliance. The international COLREGS and the USCG Navigation rules (small white book) both require the use of all available means –including radar if equipped– to determine if a risk of collision exists.
- Radar can be used for passenger safety to help identify threats or uninvited vessels approaching or traveling nearby.
- Radar can be used to locate distant storms and help provide the captain with information necessary to safely navigate through or around a storm.
- Radar can help measure distances to other objects such as land masses, aids to navigation, other ships, and storms. Radar can also confirm the ship location against a chart plotter display.
- Ship radar can signal a radar beacon (racon). When triggered, a racon transmits information back to the ship radar display about the racon feature. Often this information can be used as a navigation aid to identify a landmark or buoy.
- Radar can activate SART (Search And Rescue Transponder). SART devices are used to locate a survival craft or distressed vessel by displaying a series of dots on a rescuing ship’s radar display.
- Most importantly for ITB readers, RADAR CAN FIND BIRDS!! (We are looking for birds since birds may congregate near the same baitfish that are part of the gamefish diet.)
ARPA–automatic radar plotting aid– is a feature of commercial radar systems where the radar system automatically acquires and tracks targets (other boats) near the vessel to aid in collision avoidance. The ARPA system reports the other vessel range, bearing, target speed, target direction (course), CPA (closest point of approach), and TCPA (time of closest point of approach), safe or dangerous indication, and often includes a proximity alarm. Larger boats and commercial ships are required by IMO (International Maritime Organization) and other standards to have and use the ARPA feature on their radar. While the ARPA feature is found on commercial radars, Furuno offers it on many of its recreational radar packages as well. MARPA— Mini Automatic Radar Plotting Aid”is very similar to ARPA but includes fewer features. MARPA is currently found on most of the recreational radars. The major difference is that with MARPA, targets need to be manually selected and often a smaller number of targets can be tracked simultaneously. Note, for MARPA (or ARPA) to function accurately, a heading sensor is required. On a pleasure boat, often the heading sensor from an existing autopilot may be integrated. If not, a stand-alone heading sensor may be required. The ARPA/MARPA feature is often underused by pleasure boaters. It is a great feature to use to enhance your situational awareness, especially when traveling or operating in any kind of restricted visibility. If not familiar with this feature, try it out on a clear day when you have time to experiment at the helm. Learn how to set your system up to acquire targets and see how the system alarms you when a target gets too close. Echo trails Echo trails are a safety feature which provide colored historical trails behind a target vessel. These trails are shown on the screen in a different color to help you quickly and easily identify moving targets and potential collision threats. The trails provide a visual depiction of the vessel course. VRM and EBL Variable range markers (VRM) and electronic bearing lines (EBL) allow you to move the radar display cursor over a vessel or point of interest to view the instantaneous measurement of distance and bearing to vessels or land. Magnetrons We all hear about the magnetron inside the traditional marine radar but what does it do and why worry about transmits hours? A magnetron generates the radio pulses (radar energy) that are sent out from the marine radar antenna. After thousands of hours, the magnetron performance can be diminished. It is usually a slow degradation, starting with symptoms of reduced ability to acquire distant targets. If this happens, the radar magnetron can be replaced to restore the radar original performance. The design and technology behind the magnetron radar dates back to the 1940s military use. It wasnt until the 1980s that radar became affordable for pleasure boats. The Latest in Radar Technology Recently, a new radar design has been made available to pleasure boats. Known as Solid State, Doppler, CHIRP or FMCW radar these new radars do not operate with magnetrons. Each of the major manufactures has their own name for the solid state technology radar”names include the Furuno NXT, Garmin Fathom, Navico Halo and Navico broadband 3G/4G and Raymarine Quantum. Most manufacturers offer this technology in both open array and dome styles. The new solid state radar systems offer some advantages. These include:
- From a maintenance and service issue there is no magnetron to replace and no performance decrease as the radar operational hour increase.
- Great short range performance – some of these systems can show fine details such as finger piers inside a busy marina while 20 feet away.
- The radar is instant on, no warm up time before transmission.
- Low RF (radio frequency) emissions, safer for humans in the transmission beam.
- Solid state radar systems can indicate whether a target is moving toward or away your vessel using Doppler with programs such as Furuno Target Analyzer” and Garmin MotionScope.
- Long range performance may not be as good as with a magnetron.
- Solid State systems are not as good at finding and tracking birds as magnetron style radar.