Semi-major axis

Semi-major axis

Geodesy

Published in Basudeb Bhatta, Global Navigation Satellite Systems, 2021

The shape of a GCS’s surface is defined by a spheroid. Although the surface of the earth cannot be expressed by any regular geometrical shape—it is ‘earth-shaped’, i.e., the earth as it is with all its undulations (mountains and depressions). However, the earth is best represented by a spheroid. A sphere is based on a circle, while a spheroid (or ellipsoid) is based on an ellipse (Figure 9.4). The shape of an ellipse is defined by two radii. The longer radius is called the semi-major axis, and the shorter one is called the semi-minor axis. Rotating the ellipse around the semi-minor axis creates a spheroid. A spheroid is also known as ellipsoid. Spheroid and ellipsoid are synonymous. Word ‘spheroid’ is used in India and Britain whereas ‘ellipsoid’ is used in America and Russia.

Self-organized carpools with meeting points

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Journal Information

Published in International Journal of Sustainable Transportation, 2021

Malgorzata Miklas-Kalczynska, Pawel Kalczynski

An ellipse can be fully defined by its foci and the semi-major axis a. The foci of the neighborhood ellipses are at the destination z and the original location fk. Therefore, we used general ellipse representations to derive the lengths of semi-major axes of the neighborhood regions of fk: for the PDC and PDCH models, and for the TFC and TFCH models.

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Geodesy

Self-organized carpools with meeting points