Coordinate Systems

A coordinate system gives us a systematic way to describe where objects are located. A one-dimensional (1D) coordinate system is just a number line with an origin (the reference point, marked $O$ or $0$) and a positive direction.

Horizontal ($x$-axis)

By convention, we usually define rightward as positive and leftward as negative:

Positions to the right of the origin have positive values; positions to the left have negative values.

Vertical ($y$-axis)

By convention, we usually define upward as positive and downward as negative:

Compass directions

For navigation problems, we use compass labels: East = positive $x$ (or $+x$), West = negative $x$ (or $-x$), North = positive $y$ (or $+y$), South = negative $y$ (or $-y$):

Essential elements

...