Map Units

Map units are the units of the output map that will be generated by MapLink Pro Studio. Three types of map units will commonly be encountered:

Latitude/Longitude

Here, a unit in X is equivalent to 1° of longitude, and a unit in Y is equivalent to 1° of latitude.

Maps could be created using this form of map unit by:

• Loading data supplied in latitude/longitude.
• Loading projected data, and applying an Input Coordinate System transform to convert from the coordinate system of the input projected data back to latitude/longitude.

Projected

Here, the units in X and Y are those defined by the projection applied to the data. The physical meaning of the projected units depends strongly upon the projection. For some (but not all) projections there exists one or more lines where the scale of the projection is true. For other projections, scale is only true at a point, typically the centre of the projection. Wherever the scale of a projection is true, the projected units in X and Y are equivalent to 1 metre.

Maps could be created using this form of map unit by:

• Loading data that has already been projected into a defined coordinate system.
• Loading projected data, applying an Input Coordinate System transform to convert from input coordinate system units to latitude/longitude, and an Output Coordinate System transform to convert from latitude/longitude to projected units
• Loading data supplied in latitude/longitude (e.g. VMAP0) and applying an Output Coordinate System transform to convert from latitude/longitude to projected units

Arbitrary

MapLink Pro can handle spatial data that is defined in any coordinate system. Data is sometimes defined in arbitrary units. For example, coordinate values may be normalised so that they lie within the range 0 to 100. Alternatively, it may not be possible to recover the transformation information that would allow the data to be projected back to latitude/longitude.

In such cases MapLink Pro can be used to generate maps that remain in the original arbitrary coordinate system, or any linear transformation can be applied to the data.

Note that projections should only be applied to data that is in latitude/longitude. Where appropriate, a scale factor may be applied to data to ensure that it falls within the correct range.

Important Note

For run-time applications to be able to place objects correctly over a map using the latitude/longitude position of the object, an Output Coordinate System transform needs to be provided. Placement of objects by their map unit position is of course possible.