Today for users of geoinformation to be able to combine, reconcile and integrate spatial data from neighbouring locations for presentation then spatial referencing concepts and techniques are required to do so.
The Reference surfaces to be evaluated include: The Geoid and Ellipsoid. The Geoid is the first reference surface to be examined which is sometimes refer to as the Mean Sea Level rise above or below the Ellipsoid.
This is followed by the next reference surface called the Ellipsoid, which has two kinds: : Local Ellipsoids and Global Ellipsoids
The Ellipsoid which the second reference surface for our discussion is of two different types: Local Ellipsoid and Global Ellipsoid. The next concept is the "Vertical Datum" System.
The Vertical Datum which constitutes a reference surface for vertical positions and also known as Height Datum is of kinds as stated below: The Local Vertical Datum and Global Vertical Datum. The first kind of Vertical Datum for our discussion in this learning path is the Local Vertical Datum also known as the Local Height Datum and sometimes regarded as an approximation to the Geoid.
This then takes us to the next kind of Vertical Datum in this learning path is known as the Global Vertical Datum or Global Height Datum.
Aside Vertical Datum, there is Horizontal Datum which is also known as a Geodetic Datum constituting our next concept.
The Horizontal Datum just like the Vertical Datum has different kinds such as the Local Horizontal Datum and Global Horizontal Datum. We will first consider the Local Horizontal Datum in this learning path.
The next subject for our discussion will be the Global Horizontal as indicated below.
The next key concept we will be discussing is the Coordinate System for the position of data in space.
Map projection is the next concept for our consideration in order to understand how to represent the curved surface of the Earth on a map.
After a full comprehension of map projections, it is worth at looking the classification of map projections hence our next terminology "Projection Classification". Here at Projection Classification, we will be looking at the following: (1). Classes of Map Projection -- Cylindrical, Conical and Azimuthal ; (2). Secant Projection Classes ; (3). Projection by Distortion Property -- Conformal, Equal-area and Equidistant; and (4). Projection by Aspect.
The last concept for our operation will be Coordinate Transformation, where we will carefully consider the following: (1). 2D Polar to 2D Cartesian transformation; (2). Changing Map Projection --Forward Equation and Inverse Equation; and (3). Datum Transformation.