Читать книгу Global Navigation Satellite Systems, Inertial Navigation, and Integration - Mohinder S. Grewal - Страница 115

The apparent variations in meridional radius of curvature in Figure 3.10 are rather large because the ellipse used in generating Figure 3.10 has an eccentricity of about 0.75. The WGS84 ellipse has an eccentricity of about 0.08, with geocentric, meridional, and transverse radius of curvature as plotted in Figure 3.12 versus geodetic latitude. For the WGS84 model,

• Mean geocentric radius is about 6371 km, from which it varies by –14.3 km (–0.22%) to +7.1 km (+0.11%).

• Mean meridional radius of curvature is about 6357 km, from which it varies by –21.3 km (–0.33%) to 42.8 km (+0.67%).

• Mean transverse radius of curvature is about 6385 km, from which it varies by –7.1 km (–0.11%) to +14.3 km (+0.22%).

Because these vary by several parts per thousand, one must take radius of curvature into account when integrating horizontal velocity increments to obtain longitude and latitude.