Lowrance electronic 988-0161-011 - Manual (Page 9)

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When the echo returns, it is processed by a computer to determine rela-
tive distance, position and bearing of the object that reflected the sig-
nal. This information is displayed on the display unit's screen. Other
boats or ships, navigational markers, landmasses and the like are re-
ferred to as targets.
By knowing how long it takes for a signal to return, the distance to a tar-
get can be determined. As the radar antenna scans through a 360 degree
rotation, it can show where the target is relative to your position. By re-
peated scans, you can see which direction another vessel is moving.
The following two pages show the basic components of your radar dis-
play screen, which is commonly referred to as the PPI, an old term from
the early days of radar.