lawpax.blogg.se - Map grid

The AMG system was used until roughly the mid-90s when it was replaced with the MGA system, which is more compatible worldwide as the GDA 94 datum is almost identical to the WGS84 datum used in GPS (Global Positioning Systems). The MGA reference system uses the Universal Transverse Mercator projection of the Geocentric Datum of Australia 1994 (GDA94). As a general rule, all the new series maps have an aerial photo image on the reverse.

MGA: The MGA is the Map Grid of Australia 1994, and is used in all the new series maps.

The AMG reference system uses the Universal Transverse Mercator projection of the Australian Geodetic Datum 1966.

AMG: The AMG is the Australian Map Grid 1966/1984 system and was used on the old series maps, mostly distributed circa the 1980s.

In NSW, the 1:25000 topographic maps use either the AMG or the MGA coordinate systems. When communicating a grid coordinate, state the coordinate system first, then the grid coordinates. Maps usually have an information section that identifies the map datum and projection, along with the publisher and copyright information. Two points can be out by as little as a few hundred metres, or as much as several kilometres if there is confusion over the reference system in use.

Any given reference system is based on a datum, a 3D representation of the earth, and datums differ in how they represent land and where the location of the central frame is.