The Navigators toolbox-RADAR

 

[1]

Background

Technology has been central in the development of new tools for  the ship’s navigator and RADAR, the fourth in this series of articles, is a classic example. However it had one major advantage over the earlier tools, it did not require visibility for the navigator to see and identify objects. It could see in the dark and in dense fog, a major benefit for the navigator. It is also one of  the newer tools in the navigators toolbox having been developed in the late 19^th. century.[2] Radio Detection and Ranging (RADAR) was first used for ship detection in the early part of the 20^th. century. Its ability to detect metal objects by returned radio waves from the object was the basis of the modern marine radar.

In the early 1960’s I was a newly qualified third officer responsible for the 8-12 watch on the bridge and had a brand new Radar Observers Certificate. The scenario was one that is stressful for a navigator, to say the least!

Friday night in the Dover Strait in summer with thick fog and a moderate gale! Could not be worse as in addition to the usual commercial traffic there would be recreational boats probably caught by the weather.

This was the time to demonstrate my prowess at radar plotting. We had lookouts on the wings of the bridge, and we were at reduced speed and the foghorn on with the Captain on the bridge.

The visibility was about a hundred yards, and we relied on fog signals to narrow down where a likely ship would come from. For recreational boats we just hoped they had metal radar reflectors on board that might be picked up by our radar.

The Radar was on the port side of the bridge with a small table forward of it.

[3][4]So out came a blank radar plotting sheet and I went to the radar. In the 1960’s marine radar was quite basic. The screen was protected by a rubber hood that you must peer through  to see the screen and the screen was green with a rotating line showing the rotation of the antenna. One of the challenges was to identify proper ship and small craft echoes from what is called “clutter”, radar echoes from waves and other objects. The problem was that clutter was most dense, hiding real echoes closest the screens centre, i.e. our ship and therefore the most dangerous area relative to the ships position.

There you were constantly adjusting the cluster control seeking clearer radar images. The radar screen was aligned with the ships head so all “hits” were going to be plotted relative to the ships course, a relative bearing and most important a distance from the ship using the radar range circles on the screen. The range of the radars horizon could be adjusted and for close water work as we had that day, 3, 5 and 10 nautical miles were the  most obvious ranges to monitor.

Once a radar image is identified on the screen its relative bearing and range was measured and transferred to the plotting sheet. You then needed to wait some minutes before plotting the image once again. This gave you some important information. The line joining the two plots is the relative motion of the target and it indicates how close and what direction the target will close your own ship. No change in the relative bearing indicates you have a potential collision situating and the relative collision regulations need to be applied when necessary. If the relative bearing is increasing or reducing it indicates how the target will pass you and you can calculate the nearest approach from this plot.

Now image multiple plots needing to be assessed and you have a heavy workload. Improper plotting and/or too much reliance on the information from the radar can lead to what has become called “radar assisted collisions and  that of the collision of the “Stockholm” and “Andrea Doria” in 1956 is considered  the first of its kind.[5]

The basic rule is to use the COLREGS in sufficient time with sufficient effect that can be observed by the other vessel.

So back to the Dover Strait and my radar plotting. I duly reported the situation from my radar plots to the captain to be sternly reprimanded. “Third mate, get your binoculars and keep a watch on the wing of the bridge and stop using that new fangled instrument”! Duly chastised I followed orders.

There is a moral to this story that new technology can be implemented relatively quicky but us humans take time to adjust to them.

Thankfully, marine radar has advanced enormously since those times and as ARPA (Automatic Radar Plotting Aid) is now an integral part of electronic navigation.

References

Clipper. Français :  Feuille de Plotting Radar Au Format A3. 19 September 2017. Own work. https://commons.wikimedia.org/wiki/File:Radar_plotting_sheet_A3.pdf.

‘Collision of the Liner Stockholm and the Andrea Doria on 25 July 1956 In heavy Fog’. Accessed 3 May 2025. https://www.splashmaritime.com.au/Marops/data/less/Colreg/Casualties/Stockholm%20and%20Andria%20Doria.htm.

‘History of Radar’. In Wikipedia, 21 April 2025. https://en.wikipedia.org/w/index.php?title=History_of_radar&oldid=1286767003.

‘Poster Ship Radar Screen or Military Sonar Digital Display with Vector Targets and Submarine Traffic Tracks, Nautical Navigation Technology – Veggbilde | Europosters’. Accessed 27 April 2025. https://www.europosters.no/ship-radar-screen-or-military-sonar-digital-display-with-vector-targets-and-submarine-traffic-tracks-nautical-navigation-technology-f534014831.

‘These Three Pieces of Marine Electronics Forever Changed the Course of Boating. | Yachting’, 4 September 2015. https://www.yachtingmagazine.com/big-three/.

 

 

 

---

[1] ‘Poster Ship Radar Screen or Military Sonar Digital Display with Vector Targets and Submarine Traffic Tracks, Nautical Navigation Technology – Veggbilde | Europosters’.

[2] ‘History of Radar’.

[3] ‘These Three Pieces of Marine Electronics Forever Changed the Course of Boating. | Yachting’.

[4] Clipper, Français.

[5] ‘Collision of the Liner Stockholm and the Andrea Doria on 25 July 1956 In heavy Fog’.