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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_177</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_176.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_177</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_178.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 177</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">The same-satellite-set assumption is the biggest drawback of position-space DGPS techniques. The main advantage is that the technique can be implemented without handling raw GPS data (pseudoranges and ephemeris parameters). The user can accept and work with the receiver position outputs from two receivers. In Sec. 5.8.4 the alternative DGPS implementation approaches are summarized and compared. In Sec. 7.3 a detailed case study of the pros and the cons of position- and range-space methods for INS aiding is presented.</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>5.8.2<br />Range-Space DGPS</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 correction equations of this subsection are derived for a single satellite, but the process is identical for all satellites of interest. The GPS observables at the base and the rover are, respectively, the pseudorange measurements <img src="ea4fd0884a8c52bbd3d2da9ff45fe150.gif" border="0" alt="C0177-01.GIF" width="14" height="14" /> and <img src="011282588d19cb3b2197e3c5dc959682.gif" border="0" alt="C0177-02.GIF" width="15" height="14" />:</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="8833444f98c9320f9481506d0d5a1c9b.gif" border="0" alt="0177-01.GIF" width="394" height="47" /></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="c88ce3114a9a03ad2b0dba36ee086186.gif" border="0" alt="0177-02.GIF" width="393" height="48" /></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 the error terms are all defined as in Eq. (5.1) and the subscripts <i>o</i> and <i>r</i> denote the noncommon-mode terms corresponding to the base and the rover respectively.</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">If the rover observable <img src="10a3da6b1b63448b3ac06be952e33133.gif" border="0" alt="C0177-03.GIF" width="15" height="15" /> is replaced with <img src="22984b0b9afc46e2bf7ba25f4bb98db1.gif" border="0" alt="C0177-04.GIF" width="44" height="15" />, the result is</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="51f5a72d458eac909415ebe3dfb2b30c.gif" border="0" alt="0177-03.GIF" width="403" height="92" /></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 <img src="662b76fb05c105add606f77256f9ea60.gif" border="0" alt="C0177-05.GIF" width="292" height="20" />, <i>R</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>o</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3"> = [(<i>X - x</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>o</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">)</font><font face="Times New Roman, Times, Serif" size="2"><sup>2</sup></font><font face="Times New Roman, Times, Serif" size="3"> + (<i>Y - y</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>o</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">)</font><font face="Times New Roman, Times, Serif" size="2"><sup>2</sup></font><font face="Times New Roman, Times, Serif" size="3"> + (<i>Z - z</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>o</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">)</font><font face="Times New Roman, Times, Serif" size="2"><sup>2</sup></font><font face="Times New Roman, Times, Serif" size="3">]</font><font face="Times New Roman, Times, Serif" size="2"><sup>0.5</sup></font><font face="Times New Roman, Times, Serif" size="3">, <img src="9b1bbad2141d70a486c0bd3664c204ce.gif" border="0" alt="C0177-06.GIF" width="93" height="17" />, and </font><font face="Symbol" size="3"><i>h</i></font><font face="Times New Roman, Times, Serif" size="3"> = (MP</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>r</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> + </font><font face="Symbol" size="3"><i>h</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>r</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">) - (MP</font><font face="Times New Roman, Times, Serif" size="1"><sub><i>o</i></sub></font><font face="Times New Roman, Times, Serif" size="3"> + </font><font face="Symbol" size="3"><i>h</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>o</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3">). Note that <i>r</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>o</sub></font></i><font face="Times New Roman, Times, Serif" size="1"><sub></sub></font><font face="Times New Roman, Times, Serif" size="3"> is known because of the known location of the base receiver. Handling of the <img src="f0b7062286c2dade8451a5c47138c056.gif" border="0" alt="C0177-07.GIF" width="50" height="25" /> term will be discussed in Sec. 7.5, in which base station design is discussed. Since noncommon-mode noise </font><font face="Symbol" size="3"><i>h</i></font><font face="Times New Roman, Times, Serif" size="3"> has a standard deviation between 0.1 and 4.0 m, depending on receiver design and multipath mitigation techniques, DGPS position accuracy is much better than SPS GPS accuracy. Cancellation of the common-mode noise sources in Eq. (5.98) assumes that the rover is sufficiently near (within 1050 miles) the base station and that the corrections are available at the rover in a timely fashion. Latency compensation is discussed in Sec. 5.9.</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 common-mode noise sources are continuous and slowly time varying (see Fig. 5.13) and have significant short-term correlation (see Fig. 5.14). Denote these common-mode errors as </font><font face="Symbol" size="3">D</font><font face="Times New Roman, Times, Serif" size="1"><sub>DGPS</sub></font><font face="Times New Roman, Times, Serif" size="3">(<i>t</i>), where</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><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="965bd81e80590578fbb9aade664bdccd.gif" border="0" alt="0177-04.GIF" width="381" height="19" /></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_176.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_177</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_178.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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