Earth-Centered, Earth-Fixed Coordinate System - Fundamentals of Global Positioning System Receivers: A Software Approach - page 57

FIGURE 4.4 Vernal equinox.

FIGURE 4.5 Earth orbit around the sun.

Again referring to Figure 4.3, the x 3 -axis of the last frame discussed in the
previous section will be rotated to the vernal equinox. This transform can be
accomplished by rotating around the z 3 -axis an angle referred to as the right
ascension. This angle is in plane of the equator. The direction cosine matrix is

− sin

cos 0

C 3 = sin cos 0 ( 4 . 14 )

0 0 1