Editing Decca Navigator System (section)

=== Range and accuracy ===
During daylight, ranges of around {{convert|400|nmi|km|-1}} could be obtained, reducing at night to 200 to {{convert|250|nmi|km|-1}}, depending on propagation conditions.

The accuracy depended on:
* Width of the lanes
* Angle of cut of the hyperbolic lines of position
* Instrumental errors
* Propagation errors (for example, [[skywave]])

By day these errors could range from a few meters on the baseline up to a nautical mile at the edge of coverage. At night, skywave errors were greater and, on receivers without multipulse capabilities, it was not unusual for the position to jump a lane, sometimes without the navigator knowing.

Although in the days of differential [[Global Positioning System|GPS]] this range and accuracy may appear poor, in its day the Decca system was one of the few, if not the only, position fixing system available to many mariners. Since the need for an accurate position is less when the vessel is further from land, the reduced accuracy at long ranges was not a great problem.