Coordinate systems allows for common locations to be integrated into geographic datasets. The most commonly used coordinate system today is the latitude, longitude and height system in which the Equator(which lies halfway between the poles) and the Prime Meridian(a line through Greenwich) are reference lines used to measure latitude and longitude.
Projected coordinate systems and geodetic data are needed due to the Earth’s imperfect ellipsoid. Localised datums(such as SVY21 in Singapore’s case) can provide a more accurate representation of the area of than the global WGS 84 datum.
The coordinate systems map the Earth’s spherical surface onto a two-dimensional Cartesian coordinate plane. Thus, projected coordinate systems are referred to as map projections.