Specifications

The Transverse Mercator projection is very commonly used for topographic maps and is the
projection you are most likely to be using. The map is projected from a central meridian (line of
longitude) which is straight, the equator (a line of latitude is also straight) all other lines of longitude
and latitude are curved. Scale exaggeration increases the further away from the central meridian, this
projection therefore is only useful for a small region either side of the central meridian. Since most
maps we use only cover a relatively small region or zone these errors induced by the scale change
are too small to be important.
Also know as the
Gauss Conformal Cylindrical
projection.
Many common grid systems are based on the Transverse Mercator projection such as UTM, Gauss
Krueger, German Grid, Dutch Grid, Israeli Grid. All these grids can be setup in the
User Grid
.
The following parameters are required to use a map with a Transverse Mercator Projection. These
parameters are sometimes referred to as a
User Grid
.
Latitude Origin
- may be zero (0) degrees
Central Meridian
- Must be known for your particular map
Scale Factor
- used to set up a grid system
False Easting
- used to set up a grid system
False Northing
- used to set up a grid system
(UTM) Universal Transverse Mercator
The UTM is not really a projection in its own right but is a Grid coordinate system based on a special
case of the Transverse Mercator projection. The Latitude origin is set at 0 degrees; the Central
Meridian is the centre of one of the 60 UTM zones which circle the earth 6 degrees apart; the scale
factor is set at 0.9996; the False Easting is set at 500000; the False Northing is set at 0 for the
northing hemisphere and 10000000 for the southern hemisphere.
The Central Meridian is calculated by OziExplorer based on your calibration points.
(BNG) British National Grid
The BNG is a Grid coordinate system based on the Transverse Mercator projection, all required
parameters to set up the projection are automatically used. Also known as the OSGB grid.
(IG) Irish National Grid
The IG is a Grid coordinate system based on the Transverse Mercator projection, all required
parameters to set up the projection are automatically used.
(NZG) New Zealand Grid
This is a specific projection and a grid system only used by New Zealand. All required parameters
are known.
(NZTM2) New Zealand TM 2000
This is a specific projection and a grid system only used by New Zealand. All required parameters
are known.
(SG) Swedish Grid
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