Radar navigation

When a craft is within radar range of land or special radar aids to navigation, 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.

"[3] Parallel indexing is a technique defined by William Burger in the 1957 book The Radar Observer's Handbook.

[4] 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.

[4] This parallel line allows the navigator to maintain a given distance away from hazards.

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.