Final answer:
The orderly system of parallels and meridians drawn on a flat surface for mapmaking is known as a map projection. This system, vital for navigation and geographic representation, is based on grid systems such as those of latitude and longitude.
Step-by-step explanation:
When terms like parallels and meridians are used to describe a system drawn on a flat surface to uniquely and simply identify the location of Earth's major features, we are referring to what is known as a map projection. Map projections are essential in converting the Earth's three-dimensional shape into a two-dimensional format, allowing us to visualize geographical information on paper or digital screens.
One of the earliest and most renowned projections is the Mercator projection, developed by Gerardus Mercator in 1569, which became especially useful for navigation during sea voyages due to its ability to represent lines of constant course, known as rhumb lines, as straight segments.
The grid system used on Earth maps utilizes lines of latitude and longitude to form a network that can designate any location by its coordinates. This grid system is an example of a broader geographic coordinate system which has been improved over the centuries and is now employed in modern technologies such as GPS. The system makes use of great circles called meridians for longitude and parallel circles for latitude, allowing users to locate themselves anywhere on the planet.
The Cartesian coordinate system, named after Rene Descartes, is widely used for plotting points on a flat plane by a pair of numbers (x, y), and can be extended to three dimensions (x, y, z) for spatial representation. While this is useful for graphing and some mapping applications, geographic coordinates on a spheroidal body like Earth require the adaptation of this system into a spherical coordinate system that considers the planet's curvature.