ES 2.0 Fundamentals - Learn OpenGL ES: For Mobile Game and Graphics Development - page 109

Figure 3-16 . Normalized Device Coordinate System (landscape mode)
OpenGL ES renders an object (that is, a primitive or a combination of the same type
of primitives) using a normalized coordinate system. Normalized Device Coordinate
System ( NDCS ) is the coordinate system in which the entire screen of the device cor-
responds to a unit cube, so all points in this cube are within the range [1, 1, 1]
to [-1, -1, -1] for x, y, and z, as shown in Figure 3-17 .
Figure 3-17 . Normalized 3D space