What is the basic purpose of 10 degree drift lines?

The basic purpose of 10 degree drift lines is to estimate how many degrees off track you are while navigating. These lines are typically used in navigation charts and are part of a visual or procedural method for pilots to understand their lateral position relative to a desired flight path.

When flying, if a pilot is experiencing wind drift, these lines help them assess how much they are being pushed off course by crosswinds. By using the drift lines, a pilot can quickly gauge their deviation from the intended flight path in degrees, allowing them to make necessary corrections to maintain proper course. This tool is particularly helpful in visual navigation, ensuring pilots can effectively manage their route and avoid straying too far from their intended trajectory.