Compass FAQ
Click on any of the questions below to be taken to the answer.
  • What is a clinometer?

  • What are coordinates?

  • What does deviation mean?

  • What is special about a global compass?

  • What is grid North?

  • What does latitude mean?

  • What does longitude mean?

  • What is magnetic North?

  • What is meant by magnetic variation?

  • What is a map datum?

  • What is a New Zealand Grid reference?

  • What is the New Zealand TM?

  • What does scale on a map refer to?

  • What is meant by True North?

  • What is meant by WGS84?



  • What is a clinometer?
    It is an instrument for measuring slope angle of a line of sight. It is included in some compasses.

    What are coordinates?
    They are a pair of numbers (and/or letters) that specify a location within a spatial reference system, includes Lat/Long and NZMG.

    What does deviation mean?
    It refers to the deflection of a compass needle caused by local magnetic influences (like your equipment or vehicles).

    What is special about a global compass?
    It's is a field compass with a special hub that allows the magnet to pivot without jamming the needle. This type of compass can be used worldwide (except very near the magnetic poles).

    What is Grid North?
    It's the direction of the North-South grid lines on a map using a rectangular coordinate system. On most topographic maps, Grid North varies from True North across the map. (top...)

    What does latitude mean?
    Latitude is an angle that measures the distance of a point north or south of the Equator; more precisely, the angle that the vertical direction at the point makes with the equatorial plane. Parallels, or lines of equal latitude, are often shown on topographic maps. The Equator has a latitude of 0 degrees, and the North and South Poles are at 90 degrees.

    What does longitude mean?
    Longitude is an angle that measures the distance of a point East or West of the Greenwich Meridian, England, which is assigned a longitude of 0 degrees.(top...)

    What is magnetic North?
    The direction in which a magnetic compass needle points. Magnetic North differs from true (geographic) north, and its direction changes slowly from year to year.

    What is meant by magnetic variation?
    This is also known as Magnetic Declination. The angle measured eastward (clockwise) from true north to magnetic north at any particular location. In New Zealand in the year 2000, for example, the magnetic declination ranged from about 18 degrees in the north to 26 degrees in the south. (top...)

    What is a map datum?
    A map datum is defined in terms of a reference frame, and a reference figure. It specifies the way in which points on the three-dimensional Earth are plotted onto a reference surface, for subsequent transfer to a flat map using a specific map projection. Current NZ topographic maps are based on the Map Datum known as the New Zealand Geodetic Datum 1949 (NZGD49). This was oriented using triangulation and astronomical observations within New Zealand. A new datum is the New Zealand Geodetic Datum 2000 (NZGD2000) which is based on world-wide astronomical and satellite observations, and will be used for future topographical map series commencing in 2009..

    What is a New Zealand grid reference?
    A full grid reference is 12 numbers, made up of a 6 figure Easting and a 6 figure Northing. An abbreviated or shortened grid reference is 6 figures, made up of a 3 figure Easting and 3 figure Northing.(top...)

    What is the New Zealand TM
    This refers to New Zealand Transverse Mercator - the coordinate system that has been used on topographical maps of New Zealand since September, 2009 when it became the norm.

    What does scale on a map refer to?
    The relationship between distance on the map or chart and the ground (or sea) it represents.(top...)

    What is meant by True North? (Also referred to as Geographic North)
    The earth spins on an axis which intersects the Earth’s surface in the North and South geographic poles. True north is the direction to the true north pole from any point on the earth's surface.

    What is meant by WGS84? (World Geodetic Sytems 1984)
    This is a universal map datum used on most world nautical charts.(top...)