assignment 2

• UTM


  Universal transverse Mercator
• Latitude


  Equator is the Origin of Latitude measurement. All Latitude measurements are in the direction of North-South. Points north of the Equator are positive in latitudes and below the Equator are Negative. *(Latitude = Northings represented on the UTM)
• Longitude


  The geodetic longitude of a point is measured from the reference plane and a plane passing through the point, both planes (latitude & Longitude) being perpendicular to the equatorial plane.
• Prime Meridian


  Prime Meridian as the origin of the Longitude.
• Geodesy


  The Science which determines the Shape and the Size of the Earth, the Precise Positions and Elevations of points, Lengths and Direction of lines on the earth's surface, and the Terrestrial Gravity and its Variations.
• Ellipsoid


  Reference ellipsoids are usually defined by semi-major (equatorial radius) and flattening (the relationship between equatorial and polar radii). It is the mathematical surface that best fits the physical earth.
• Easting


  Eastings are measured from the central meridian (with a 500km false easting to insure positive coordinates).
• Northing


  Northings are measured from the equator (with a 10,000km false northing for positions south of the equator).
• Geographic Coordinate System


  Latitude, Longitude, and Height (Ф, , Ht)
• Equator is the Origin of Latitude measurement. All Latitude measurements are in the direction of North-South. Points north of the Equator are positive in latitudes and below the Equator are Negative. *(Latitude = Northings represented on the UTM)
• The Prime Meridian is Zero meridian that runs along Greenwich, in Great Britain. This Zero Meridian is the starting line for all the Meridians measured to the West and East directions, towards PNG. It runs from Zero to 180º East and Zero to 180° West. Only One line of Meridian defines the origin of the Longitude. (Longitude = Eastings represented in UTM Format)
• Earth Centered, Earth Fixed X, Y, and Z

  Earth Centered, Earth Fixed Cartesian coordinates are also used to define three dimensional positions. Earth centered, earth-fixed, X, Y, and Z, Cartesian coordinates (XYZ) define three dimensional positions with respect to the center of mass of the reference ellipsoid.
• The Origin of the ECEF Cartesian Coordinates is the Centre of Physically Earth Defined by the GPS. The Z-axis points toward the North Pole. This is also the direction of the Polar Axis, the Minor (b) The X-axis is defined by the intersection of the plane defined by the prime meridian and the equatorial plane. The Y-axis completes a right handed orthogonal system by a plane 90° east of the X-axis and its intersection with the equator. This is along the plane of the Equator ECEF coordinate systems are very useful for Datum and System transformation.
• UNIVERSAL TRANSVERSE MACATOR (UTM) SYSTEM


  The most used system by surveyors. The system is in meters where points are defined by the UTM Eastings and UTM Northings from an origin. Origin of the UTM Eastings fall on the Central Meridian of any specified Zone. The One Tenth Millionth m defined from the Equator falls as the Origin of the Northing direction measurements.
• Datum


  Point of reference where all the measurements are tied to.
• Horizontal Datum


  Reference of the Horizontal on the Geographic reference system Latitude, Longitude and the projected coordinates in UTM Eastings and Northings.
• Vertical Datum


  Reference of heights defined by the Ellipsoid Heights.
• WGS84


  Earth Centered Earth Fixed World Geodetic System 1984. World Geodetic Datum
• ITRF


  International Terrestrial Reference Frame
• PNG94


  PNG 94 is national Datum for PNG.
• Geoid


  It is an equipotential surface in terms of gravity which means that at any point it is perpendicular to the direction of gravity. This can be depicted as a mathematical surface and suitable as a reference surface for gravity potential or height differences. Therefore, this has been accepted as datum or reference surface for defining vertical locations/surface relief.
• EGM2008


  Earth Gravity Model 2008. World Gravity model where all the heights are fixed on the physical surfaces taking into accounts the effects of Earth's gravity on measurements using GPS/GNSS measurements.
• Reference Ellipsoids


  Reference ellipsoids are usually defined by semi-major (equatorial radius) and flattening (the relationship between equatorial and polar radii)
• Earth Surfaces


  • The topographical surface of the earth is the actual surface of the land and sea at some moment in time.
• Geoid models


  • Attempt to represent the surface of the entire earth over both land and ocean as though the surface resulted from gravity alone.
• Reference ellipsoids used in other nations

  • List at least 5
• Global Datum


  Geocentric ECEF Datum which the parameters captures the globe
• National Datum


  Reference to the Geodetic surface of the particular region at a point in time and the parameters defers by some mm and it is used locally. Eg: WGS84 is a global datum whereas PNG94 is a National Datum for PNG alone.