# Scale factor

From AMS Glossary

## scale factor

(

*Also called*map scale, map factor.) The ratio between the distance separating two points on a map of the earth's surface at a standard latitude (or latitudes) and the distance between the corresponding points on the earth's surface itself.For most map projections, this factor is a slowly varying function of latitude, and for synoptic- chart base maps it is usually of the order of 10

^{-6}to 10^{-7}. The scale factor is sometimes defined as the reciprocal of the above ratio.*Compare*conformal map.