b. Laborde Projection. This projection is used to
map the island of Madagascar. It is an Oblique
Mercator type projection with the long axis of the
cylinder oriented at 18° 54' East of North. Scale factor
at the origin is 0.9995. This projection is used with the
International Ellipsoid.
c. West Malaysia Rectified Skew Orthomorphic
(RSO) Projection. This projection is used to map the
islands of Malaysia. It is an Oblique Mercator type
projection with the long axis of the cylinder oriented at
36° 58' 27.1542" East of North. Scale factor at the
origin is 0.99984. This projection is used with the
Modified Everest Ellipsoid to map the West Malaysia
RSO Grid System.
d. Many other Oblique Mercator Projections are used
to map areas of the world. Most are designed to work
with a specific grid system like the West Malaysia
system described above. Examples of these systems
include, but are not limited to, the following:
Alaska Zone 1 RSO
Borneo RSO
Great Lakes (4 Zones) RSO
Liberia RSO
Malaya (chain) RSO
Malaya (yard) RSO
Switzerland Oblique Mercator
3-12 New Zealand Map Grid Projection
The New Zealand Map Grid Projection (NZMG)
is used to map New Zealand. It is a "sixth-order
complex-algebra polynomial modification" of the
Mercator Projection. A cylinder cannot necessarily be
considered in this projection; it is a mathematical
projection set secant to the International Ellipsoid.
The NZMG has no defined scale factor at the central
meridian, scale factor ranges from 1.00023 to 0.00078
over the entire projection.
3-13 Cassini Projection
a. The Cassini Projection can be viewed outwardly as
a Gauss-Kruger projection in that the cylinder is
transversed 90° from the Mercator Projection and is
also tangent to the ellipsoid at the central meridian of a
zone. The Cassini Projection; however, predates the
Gauss-Kruger and Transverse Mercator Projections.
The projection is made by treating all meridians as
planes which extend from the ellipsoid out to the
cylinder. This projection causes the equator and
central meridian to be perpendicular straight lines. All
other meridians appear as lines which intersect the
equator at right angles and curve toward the central
meridian except for those meridians which are located
90° from the central meridian. Those meridians
appear as straight lines which are parallel to the
equator. Scale factor at the Cental Meridian is unity
(1.00 or exact). This projection is still used in some
areas for civil and local grid systems; however, it is
considered obsolete for most purposes and in many
areas has been replaced by the Transverse Mercator
Projection. This projection is sometimes referred to as
the Cassini-Solder Projection.
b. Some of the local grids which use the Cassini
Projection and may still be available are:
Cyprus Grid-superseded in 1967
English Grid-superseded in 1950
Irish Grid-superseded in 1976
Jahore Grid-superseded in 1967
Malay Grid-superseded in 1967
Palestine Civil-still in use
c. Position differences between Cassini grid systems
and Transverse Mercator grid systems are slight. For
example, northing is the same in the Palestine Cassini
Civil Grid as it is in the Palestine Transverse Mercator
Civil Grid. The easting difference between the two is
zero at 20 Km from the central meridian and only 4.1
meters at 100 Km from the central meridian.
Table 3-2
Table 3-3
Table 3-4
DRAFT
3-14