📄 page_223.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_223</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_222.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_223</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_224.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 223</font></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">second column of data contains the WGS-84 parameters that underlie the GPS system equations [54].</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>6.6.2<br />Gravity Model</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">In several references [18, 66, 115, 117, 155] models of the earth gravitational attraction and centripetal acceleration are discussed. The resultant gravity vector varies as a function of position because of the gravitational attraction being a function of geocentric radius, the centripetal acceleration being a function of latitude and radius, and the nonuniform earth mass distribution. The following discussion is based on the models in Refs. 18 and 66.</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">In the geographic reference frame, the local gravity vector is defined to be</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="13c3aa9cd8e79fe45aaf8e4ebbd1b1be.gif" border="0" alt="0223-01.GIF" width="323" height="60" /></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">where</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="0b8dfd40fa9379a63cf94c6f13fc455a.gif" border="0" alt="0223-02.GIF" width="445" height="36" /></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="bd32d15918da1b91b420800ce5009079.gif" border="0" alt="0223-03.GIF" width="459" height="36" /></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 geodetic and gravity model parameters are defined in Table 6.3. The relations between these various constants and the parameters of the gravity model, as derived in Ref. 66, are presented in Table 6.4. The resulting local gravity formulas when the WGS-84 parameters are used are</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="e5f2ec57c6c84bfddc851b6af954875b.gif" border="0" alt="0223-04.GIF" width="471" height="20" /></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="23bc41369be9ced2d488373b1c4cc209.gif" border="0" alt="0223-05.GIF" width="485" height="44" /></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">where <i>h</i> is measured in meters. Equation (6.138) is accurate to approximately 0.1 x 10</font><font face="Times New Roman, Times, Serif" size="2"><sup>-6</sup></font><font face="Times New Roman, Times, Serif" size="3"><i>g</i>, which is less than the magnitude of the gravity anomaly terms </font><font face="Symbol" size="3">z</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> and </font><font face="Symbol" size="3">h</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3">. The term </font><font face="Symbol" size="3">d</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> is, strictly speaking, not a gravity anomaly, but a modeling error due to either inaccurate parameters or the neglected higher-order terms in the approximation. An alternative model that accounts for the variation in </font><font face="Symbol" size="3">z</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> with altitude is discussed on page 10 of Ref. 153.</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">Characteristics of the gravity anomaly are discussed in Refs. 18 and 53. The characteristics of </font><font face="Symbol" size="3">D</font><font face="Symbol" size="3"></font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> = [</font><font face="Symbol" size="3">z</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Symbol" size="3">h</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Symbol" size="3">d</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3">], their effect on INS performance, and the appropriate modeling approach are application dependent. For a stationary system, </font><font face="Symbol" size="3">D</font><font face="Symbol" size="3"></font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> is constant and indistinguishable from the accelerometer biases. When the INS is nonstationary, the rate of change of </font><font face="Symbol" size="3">D</font><font face="Symbol" size="3"></font><font face="Times New Roman, Times, Serif" size="1"><sub><i>g</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> is velocity dependent. In</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_222.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_223</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_224.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -