Modified transverse Mercator

The modified transverse Mercator (MTM) coordinate system is a metric grid-based method of specifying locations, similar to the Universal Transverse Mercator coordinate system (UTM). However, MTM uses a transverse Mercator projection with zones spaced 3° of longitude apart, one half of the spacing of UTM zones.

Due to its narrower zones, MTM exhibits a scale factor of 0.9999 (distortion of 1:10,000) in the midpoint of a zone, versus 0.9996 (1:2,500) for UTM. This makes it more suitable for land surveying, with its target maximum distance (closure) error of 1:5000.^[1]

The MTM coordinate system is used by various government institutions in Canada in particular.^[2][3][4] It is conceptually similar to the Gauss-Kruger coordinate system historically used in parts of continental Europe, even though the parameters (and scale factor) are different.