Gauss and UTM Conformal Projections and the Plane Rectangular Coordinate System - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 272

Fig. 6.3 Geometric description of the Gauss projection (a) elliptical cylinder being tangential to
the ellipsoid and (b) developed plane of the elliptic cylinder
determine the projection formula ( 6.1 ) according to these three conditions for Gauss
projection will be discussed in Sect. 6.4 .
6.3.3 Zone-Dividing of the Gauss Projection
Reasons for Zone Division
In the Gauss projection, except for the central meridian, any other line segments
will be distorted after projection and the distortion increases with the distance from
the central meridian. Such distortion of distance is harmful and should be kept
within small limits to reduce its effect on mapping and map application. The most
effective way to limit the distortion of distance is by “zone-dividing” projection. To
be specific, the globe is divided into narrow zones along meridians that are all of
equal degrees width in longitude (e.g., 6 or 3 wide in longitude). Each zone is
projected separately to get several different projection zones. The meridian at the
center of each zone is called the central meridian, which is projected as the ordinate
axis. Hence, the central meridian is also known as the axial meridian. The meridian
used to divide the projection zones (at the edge of a projection zone) is called the
dividing meridian.
Because a zone division limits the projection area to within a narrow area of the
two sides of the central meridian, the distance distortion is effectively restricted.
Evidently, within a certain area, zones become narrower as the number of zones
increases, and the distortion of distances will correspondingly become smaller. In
terms of limiting distortions of distance, the more zones divided, the better.
After the zone-dividing projection, each projection zone has unique coordinate
axes and coordinate system origins. Thus, a mutually independent Gauss plane
coordinate system has formed and points on the two sides of the dividing meridian
belong to two different coordinate systems. In productive operations, the areas of