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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_26</title> <link rel="stylesheet" href="reset.css" type="text/css" media="all"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <table summary="top nav" border="0" width="100%"> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_25.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_26</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_27.html">next page ></a></td> </tr> <tr> <td id="ebook_page" align="left" colspan="3" style="background: #ffffff; padding: 20px;"> <table border="0" width="100%" cellpadding="0"><tr><td align="center"> <table border="0" cellpadding="2" cellspacing="0" width="100%"><tr><td align="left"></td> <td align="right"></td> </tr></table></td></tr><tr><td align="left"><p></p><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td align="right"><font face="Times New Roman, Times, Serif" size="2" color="#FF0000">Page 26</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td align="center"><font face="Times New Roman, Times, Serif" size="3"><img src="3bc0466841d15326bbaa28679006f597.gif" border="0" alt="0026-01.GIF" width="224" height="188" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td align="center"><font face="Times New Roman, Times, Serif" size="2">Figure聽2.4<br />ECEF聽rectangular聽coordinate聽system.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><i>2.2.1<br />ECEF Rectangular Coordinates</i></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">The usual rectangular coordinate systems (<i>x</i>, <i>y</i>, <i>z</i>)</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>e</i></sub></font><font face="Times New Roman, Times, Serif" size="3">, herein referred to as the ECEF coordinate system, has its <i>x</i> axis extended through the intersection of the prime meridian (0掳 longitude) and the equator (0掳 latitude). The <i>z</i> axis extends through the true north pole (i.e., parallel to the earth's spin axis). The <i>y</i> axis completes the right-handed coordinate system, passing through the equator and 90掳 longitude, as shown in Fig. 2.4.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><i>2.2.2<br />ECEF Geodetic Coordinates</i></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">As described in Sec. 2.1, the earth's geoid is approximated by an ellipsoid of revolution about its minor axis. The eccentricity of the geoid is determined by the earth's gravitational attraction and angular rotation rate. Therefore the defining parameters for a geodetic system must be defined consistently. The defining parameters are major axis length (<i>a</i>), eccentricity (<i>e</i>), inertial rate of rotation (</font><font face="Symbol" size="3"><i>w</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>ie</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">), and equatorial effective gravity (</font><font face="Symbol" size="3"><i>g</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>e</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">). There are different defining ellipsoids, and therefore the user must reference a geodetic position to a particular defining ellipsoid. The WGS-84 ellipsoid [3] is defined by</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="5f52b34d2a73744045eb0262e4bb4cb9.gif" border="0" alt="0026-02.GIF" width="285" height="45" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">The WGS-84 ellipsoid is generated when an ellipse is rotated about its minor axis. The minor axis passes through the true north and the true south poles, as shown in Fig. 2.5. Most charts and navigation tools are expressed in the (</font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Symbol" size="3"><i>f</i></font><font face="Times New Roman, Times, Serif" size="3">, <i>h</i>) geodetic coordinates, where </font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3"> denotes latitude, </font><font face="Symbol" size="3"><i>f</i></font><font face="Times New Roman, Times, Serif" size="3"> denotes longitude, and <i>h</i> denotes altitude. Latitude (</font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3">) is the angle between the ellipsoidal normal <i>N</i> and the equatorial plane. Note that the extension of the normal toward the interior of the WGS-84 ellipsoid will not intersect the center of the earth. Longitude (</font><font face="Symbol" size="3"><i>f</i></font><font face="Times New Roman, Times, Serif" size="3">) is the angle in the equatorial plane between the prime meridian and the projection of the point of interest onto the equatorial plane. Altitude (<i>h</i>) is the distance along the ellipsoidal normal, away from the interior of the ellipsoid, between the surface of the ellipsoid and the point of interest.</font><font face="Times New Roman, Times, Serif" size="3" color="#FFFF00"></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table><p><font size="0"></font></p>聽 </td> </tr> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_25.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_26</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_27.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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