14.02.2013 Views

Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Appendix E / Earth Geometry<br />

_ _<br />

ELLIPSOID<br />

Table 18-1 : Local Earth Reference Ellipsoids<br />

SEMI-MAJOR<br />

AXIS ( RA )<br />

18-4<br />

SEMI-MINOR<br />

AXIS ( RB )<br />

DATE AREA<br />

Clarke 6 378 206 6 356 584 1866 North America<br />

Clarke 6 378 249 6 356 480 1880 France,North Africa<br />

International 6 378 388 6 356 912 1924 Europe<br />

Mod Airey (OS) 6 378 563 6 356 257 1936 Great Britain<br />

Krassowski 6 378 245 6 356 836 1940 Russia<br />

WGS 72 6 378 135 6 356 751 1972 USA DoD<br />

WGS 84 6 378 137 6 356 752 1984 USA DoD (GPS)<br />

The variation in the Earth radii with latitude derived in the following subsections<br />

is shown in Figure 18-2.<br />

.<br />

PRINCIPLE EARTH RADII ( METRES )<br />

x 106<br />

6.4<br />

6.39<br />

6.38<br />

6.37<br />

6.36<br />

6.35<br />

6.34<br />

GEODETIC RADIUS<br />

MERIDIAN RADIUS<br />

EARTH RADIUS<br />

6.33<br />

0 10 20 30 40 50 60 70 80 90<br />

LATITUDE ( DEGREES )<br />

Figure 18-2 : Principle Earth Radii for Navigation<br />

The geocentric radius (Rr,d) is a function of the polar and meridian radii<br />

(Rpd) and (Rmd).<br />

r,<br />

d<br />

2<br />

pd<br />

2<br />

d<br />

2<br />

md<br />

P : = R ⋅ sin λ + R ⋅ cos λ<br />

2<br />

d<br />

Equation 18.1-1<br />

When dealing with terrestrial navigation over long distances the term<br />

Nautical mile is often used which is equivalent to 1 arc-second, or 1852 m.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!