Editing Navigation (section)

====Radar navigation====
{{Further|Radar navigation|Doppler radar#navigation}}

Radars can be used for navigation and [[Marine radar|marine radars]] are commonly fitted to ships for navigation at sea.<ref name="e303">{{cite book | title=Safe Nav Watch | publisher=[[Witherby Publishing Group]] | publication-place=Livingston, Scotland | date=2023 | isbn=978-1-914993-46-6 | page=37}}</ref> Radar is an effective aid to navigation because it provides ranges and bearings to objects within range of the radar scanner.<ref name="Anwar133">{{cite book | last = Anwar | first = Nadeem | title = Navigation Advanced for Mates and Masters | edition = 2nd | date = 2015 | publisher = [[Witherby Publishing Group]] | location = Edinburgh | pages=133–139 |isbn = 978-1-85609-627-0}}</ref> When a vessel (ship or boat) is within radar range of land or fixed objects (such as special radar aids to navigation and navigation marks) the navigator can take distances and angular bearings to charted objects and use these to establish arcs of position and lines of position on a chart.<ref name="chap744">Maloney, 2003:744.</ref> A fix consisting of only radar information is called a radar fix.<ref name="bow816">Bowditch, 2002:816.</ref> Types of radar fixes include "range and bearing to a single object,"<ref name="nima163">National Imagery and Mapping Agency, 2001:163.</ref> "two or more bearings,"<ref name="nima163"/> "tangent bearings,"<ref name="nima163"/> and "two or more ranges."<ref name="nima163"/> Radar can also be used with [[ECDIS]] as a means of position fixing with the radar image or distance/bearing overlaid onto an [[Electronic navigational chart|Electronic nautical chart]].<ref name="Anwar133"/>

Parallel indexing is a technique defined by William Burger in the 1957 book ''The Radar Observer's Handbook''.<ref name="nima169">National Imagery and Mapping Agency, 2001:169.</ref> This technique involves creating a line on the screen that is parallel to the ship's course, but offset to the left or right by some distance.<ref name="nima169"/> This parallel line allows the navigator to maintain a given distance away from [[navigational hazard|hazards]].<ref name="nima169"/> The line on the radar screen is set to a specific distance and angle, then the ship's position relative to the parallel line is observed. This can provide an immediate reference to the navigator as to whether the ship is on or off its intended course for navigation.<ref name="Victor">{{cite book | last = Victor| first = Alain| title = Parallel Index Techniques in Restricted Waters -| edition = 2nd | date = 2020 | publisher = [[Witherby Publishing Group]] | location = Edinburgh |isbn = 9781856099165}}</ref>

Other techniques that are less used in general navigation have been developed for special situations. One, known as the "contour method," involves marking a transparent plastic template on the radar screen and moving it to the chart to fix a position.<ref name="nima164">National Imagery and Mapping Agency, 2001:164.</ref> Another special technique, known as the Franklin Continuous Radar Plot Technique, involves drawing the path a radar object should follow on the radar display if the ship stays on its planned course.<ref name="nima182">National Imagery and Mapping Agency, 2001:182.</ref> During the transit, the navigator can check that the ship is on track by checking that the pip lies on the drawn line.<ref name="nima182"/>