Linear scale

The scale bar is a mark or scale at the edge of a map, a plan or a map is drawn on the scale and labeled with the real distances. The scale bar facilitates the measurement on the map and its length should be accurate to 0.5 mm.

Another advantage of the scale bar is that a map provided therewith or illustration is also useful in changes in their size. Often maps or sketches can be reduced without the scale designation is corrected accordingly.

A scale bar can - also be implemented optically or digitally, eg in the eyepiece of instrumentation in a reticle ( also indirectly as a size of a cross mark ) and on digital map - except on paper.

Scale bars were before the mid-19th century, mostly the only scale indication on maps. In extreme cases, up to twenty different scale bars are specified for different length dimensions.