Map Definition File

The map definition file (mapdef.dat) contains a list of coordinate reference systems.

Do not edit this file. Create a copy and use the copy for custom map definitions.

[UTM - NAD83]

UTM-24N-Nad83,"Zone 24N (42 W TO 36 W)",NEMR,NA83,UM,0,0,0,500000,0.9996,0,-39,0

UTM-25N-Nad83,"Zone 25N (36 W TO 30 W)",NEMR,NA83,UM,0,0,0,500000,0.9996,0,-33,0

UTM-26N-Nad83,"Zone 26N (30 W TO 24 W)",NEMR,NA83,UM,0,0,0,500000,0.9996,0,-27,0

UTM-27N-Nad83,"Zone 27N (24 W TO 18 W)",NEMR,NA83,UM,0,0,0,500000,0.9996,0,-21,0

Map definition entries are collected in groups. The group name, enclosed in square brackets, is on a line by itself, followed by an unlimited number of definitions, one per row. Each definition can be no longer than 400 characters.

Definition fields are separated by commas. The first five fields are required. The remaining fields (the numeric fields) depend on the CRS and projection. If a numeric field is not required, enter a value of 0. You cannot omit a field.

Field	Type	Maximum	Description	Example
Key	Char	20 characters	The map definition key. Must be unique.	`UTM-24N-Nad83`
Description	Char	80 characters	A description for the definition. Must be enclosed in double quotes. Must contain no commas.	`"Zone 24N (42 W TO 36 W)"`
Coordinate system	Char	4 characters	NEMR, NRMR, LLDG or CHMR (see table below)	`NEMR`
Ellipsoid	Char	4 characters	From the datum file. See Datum File	`NA83`
Projection	Char	4 characters	Projection code. See the list below.	`UM`
Scaling latitude 1	Real	10 dec. places	The latitude of the geographic origin.	`0`
Scaling latitude 2	Real	10 dec. places	The latitude of the geographic origin	`0`
False North	Real	10 dec. places	An offset applied to all northings.	`0`
False East	Real	10 dec. places	An offset applied to all eastings.	`500000`
Scaling factor	Real	10 dec. places	The amount of distortion to be expected at the geographic origin.	`0.9996`
Latitude origin	Real	10 dec. places	The latitude of the geographic origin.	`0`
CMorLO	Real	10 dec. places	Central meridian or longitude origin, depending on the projection.	`-39`
Skew azimuth	Real	10 dec. places	The azimuth of a great circle, in degrees east of north, which passes through a point of origin.	`0`

Coordinate System	Description
NEMR	The coordinates are expressed as Northings and Eastings of a projection in metres on the ground (hence Northings and Eastings in MetRes). NEMR is a projected coordinate system. Projected systems, such as Universal Transverse Mercator (UTM), Stereographic, or Mercator provide their own mechanisms to project maps of the earth's surface onto a two-dimensional Cartesian coordinate plane.
NRMR	Coordinates expressed in metres on the map have no reference to a specific location on the ground (hence Non Registered, MetRes). This type of coordinate system is used when the information necessary for relating the map to the real world (control points) is not necessary or not available.
LLDG	Coordinates are expressed in latitude and longitude in decimal degrees on a reference ellipsoid (hence Latitude and Longitude in Decimal deGrees).
CHMR	Coordinates are expressed in metres at the chart scale (hence CHart in MetRes). This coordinate system is used primarily for hydrographic charting. A CHMR CRS contains a projected CRS as well as an affine transformation which relates projected coordinates to paper space. CHMR, NEMR and LLDG CRSs all provide a framework for defining real-world locations.

Projection	EPSG Projection Definition	Code
Alaska Zone 1¹	A1 OBLIQUE MERCATOR VARIANT A ("EPSG", "9812")	A1
Azimuthal	AZIMUTHAL EQUIDISTANT ("EPSG", "9832")	AZ
Cassini	CASSINI SOLDNER ("EPSG", "9806")	CA
Gnomonic	OBLIQUE AND_EQUATORIAL STEREOGRAPHIC ("EPSG", "9809")	GN
Google Mercator	PSEUDO MERCATOR ("EPSG", "1024")	GM
Hotine Oblique Mercator A	OBLIQUE MERCATOR VARIANT A ("EPSG", "9812")	HB
Hotine Oblique Mercator B	OBLIQUE MERCATOR VARIANT B ("EPSG", "9815")	OM
Lambert Conformal Conic	LAMBERT CONIC CONFORMAL_2SP ("EPSG", "9802")	LC
Mercator A	MERCATOR VARIANT A ("EPSG", "9804")	ME
Mercator B	MERCATOR VARIANT B ("EPSG", "9805")	MR
Polyconic	AMERICAN POLYCONIC ( "EPSG", "9818")	PO
Polar Stereographic	POLAR STEREOGRAPHIC VARIANT A ("EPSG", "9810")	PS
Rectified Skew Orthomorphic	No EPSG reference	RS
Stereographic	OBLIQUE AND EQUATORIAL STEREOGRAPHIC ("EPSG", "9809")	ST
Transverse Mercator	TRANSVERSE MERCATOR ("EPSG", "9807")	TM
Universal Transverse Mercator	TRANSVERSE MERCATOR ("EPSG", "9807")	UM

¹ A1 is a special projection with all hard-coded values

When creating a new entry, the numeric fields you have to consider depend upon the coordinate system and projection.

Fields	Projections
Fields	CA	GN	HB	LC	ME	PO	PS	RS	ST	TM	UM
Scaling lat 1	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	CHMR
Scaling lat 2				NEMR CHMR	NEMR
False northing	NEMR	NEMR	NEMR	NEMR	NEMR		NEMR	NEMR	NEMR	NEMR
False easting	NEMR	NEMR	NEMR	NEMR	NEMR		NEMR	NEMR	NEMR	NEMR
Scaling factor	NEMR CHMR	NEMR	NEMR	NEMR CHMR		CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR
Central meridian/longitude origin	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	NEMR CHMR	CHMR
Skew azimuth								NEMR CHMR

Fields that contain a marker may require a value, depending on the definition. If it turns out that a particular field is not required, it should contain a 0 in the map definition entry.

In a NEMR coordinate system, the coordinates are expressed as Northings and Eastings of a projection in metres on the ground. Distances and bearings can be carried across adjacent map sheets with this coordinate system.

This table shows which fields you may require for a map definition using a NEMR coordinate system. Any field with no marker is not required and should contain a 0.

Field	Projection
Field	A1	AZ	CA	GN	HB	LC	ME	P0	PS	RS	ST	TM	UM
Scaling latitude 1	*											
Scaling latitude 2							
False northing												
False easting												
Scaling factor												
Latitude origin	*
Central meridian/longitude origin												
Skew azimuth										

* For the A1 projection, you must include the same value in both scaling latitude 1 and latitude origin.

In an LLDG coordinate system, coordinates are expressed in latitude and longitude in decimal degrees on a reference ellipsoid.

This table shows which fields you may require for a map definition using an LLDG coordinate system.

Field	Projection
Field	A1	AZ	CA	GK	GN	HB	LC	ME	P0	PS	RS	ST	TM	UM
Scaling latitude 1
Scaling latitude 2
False northing
False easting
Scaling factor
Latitude origin														
Central meridian/longitude origin														
Skew azimuth

In a CHMR coordinate system, Coordinates are expressed in metres at the chart scale. All distances and bearings are relative to that chart.

This table shows which fields you may require for a map definition using a CHMR coordinate system.

Field	Projection
Field	AZ	CA	GN	HB	LC	ME	P0	PS	RS	ST	TM	UM
Scaling lat 1												
Scaling lat 2					
False northing
False easting
Scaling factor											
Latitude origin
Central meridian/longitude origin												
Skew azimuth									