Gauss and UTM Conformal Projections and the Plane Rectangular Coordinate System - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 273

interest usually cross between different zones and have to be transformed into the
same coordinate system, so a transformation of coordinates between different
projection zones is necessary (called the transformation between adjacent zones).
Considering this, the area of interest should not be divided into too many zones.
When dividing an area into zones, both of the above-mentioned aspects should
be taken into account. There are two methods of zone division; namely, that of the
zones 6 wide (each zone is 6 of longitude in width) and that of the zones 3 wide
(each zone is 3 of longitude in width). The former can be used for medium- and
small-scale mapping and the latter for large-scale mapping. The plane rectangular
coordinates of the geodetic points should be computed within the zones 6 wide
according to the Gauss projection. In areas with 1:10,000 or much larger scale
mapping, the plane rectangular coordinates in the 3

zones should also be

computed.

Methods of Zone Division

Figure 6.4 depicts the Gauss projection in zones 6 wide. Starting from 0 ∘ meridian
eastward, each zone is 6 of longitude in width, numbered 1 to 60. The central
meridians in each zone are of longitudes 3 ∘ ,9 ∘ ,

, up to 357 ∘ . We assume that the
zone is numbered n, and the central meridian is of longitude L 0 , hence:

...

9
=
; :

6 ∘ 3 ∘ L 0 ﾼ n

3 ∘ ð L 0 þ Þ

ð 6 : 17 Þ

n ﾼ

6

Given the geodetic longitude L of a certain point, the zone number of this point
for a projection in zones of 6 width can be computed according to:

L
6

n ﾼ ð take integer quotient Þ þ 1 if there is a remainder ð Þ:

The 3 zones are divided based on the 6 zones. The central meridians in even-
numbered zones coincide with those in the zones 6 wide. The central meridians in
odd-numbered zones coincide with the zone-dividing meridians in the zones 6
wide. The specific zone dividing starts from the meridian of east longitude 1.5
eastward; each zone is 3 of longitude in width, numbered 1 to 120 as shown in
Fig. 6.4 . Setting the zone number to n 0 , the longitudes of the central meridians in
each zone are:

3 ∘ n 0 L 0 ﾼ

ð 6 : 18 Þ

n 0 ﾼ L 0 = 3

Given the geodetic longitude L of a point, the zone number of this point for a
projection in zones of 3 width can be computed according to: