Page 188 - Digital Analysis of Remotely Sensed Imagery

Image Geometric Rectification 153

180°
6 °
90°W Y Z 90°E
6 °
180° 168° 156° 30° 24° 18° 12° 6° 0° 6° 12° 18° 24° 30° 156° 168° 180°
84°
X
72°
W
64°
V
P
6°
N
0°
M
6°
L
64° E
D
72°
C
80°
1 2 3 4 5 26 27 28 29 30 31 32 33 34 35 56 57 58 59 60

90°W A B 90°E

180°
FIGURE 5.6 Distribution of grid zones in the UTM system around the globe.
Each 6° latitude by 8° longitude quadrilateral is identifi ed by its column
number and row letter. The tinted zone is 29M.

which coordinates are measured northing and easting in meters. The
northing values start from zero at the equator in a northerly direction.
The equator has a northing value of 0 m in the northern hemisphere.
For northings in the southern hemisphere, the origin is defined as a
point 10,000,000 m south of the equator in order to avoid negative
coordinates. Similarly, a central meridian through the middle of each
6° zone is assigned an easting value of 500,000 m. Grid values to the
west of this central meridian are smaller than 500,000; to the east,
larger than 500,000. Because the same coordinate system is applied to
all zones and to both hemispheres, it is necessary to add the UTM
longitudinal zone in front of the easting value and the hemisphere
(e.g., N or S) after the coordinates to differentiate the location, for
instance, (510,000E, 4,970,000N).

5.2.2 NZMG
Similar to the UTM, the NZMG is also a conformal projection that
was devised specially for New Zealand because of its elongated