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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_280</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_279.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_280</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_281.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 280</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">where <i>n</i> is the integer number of the code clock bias resets, which is straightforward to track. Therefore the clock bias correction described in Sec. 7.5.2 can also be used to compensate the phase corrections.</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">7.5.5.2<br />Base Station Phase Integer Ambiguity Specification</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">Repeating Eq. (5.62), the differentially corrected phase measurements at a rover will be defined as</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="bd14fc3d9fbb1259f0753723d7e31fc6.gif" border="0" alt="0280-01.GIF" width="463" height="22" /></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="aa9f05778cb83774a3e9c4f6af1b1053.gif" border="0" alt="NN.GIF" width="74" height="19" /> is the difference between the rover and the base integer ambiguities. Since the rover does not know <img src="043dd80643b070cc8d899a779f7a2759.gif" border="0" alt="NIO.GIF" width="26" height="19" /> and cannot estimate <img src="043dd80643b070cc8d899a779f7a2759.gif" border="0" alt="NIO.GIF" width="26" height="19" /> separately from <i>N</i></font><i><font face="Times New Roman, Times, Serif" size="2"><sup>(i)</sup></font></i><font face="Times New Roman, Times, Serif" size="2"><sup></sup></font><font face="Times New Roman, Times, Serif" size="3">, the value of <img src="043dd80643b070cc8d899a779f7a2759.gif" border="0" alt="NIO.GIF" width="26" height="19" /> is immaterial to the rover, as long as it is a fixed integer. If the value <img src="043dd80643b070cc8d899a779f7a2759.gif" border="0" alt="NIO.GIF" width="26" height="19" /> were to change, the rover would perceive the change in <img src="aa9f05778cb83774a3e9c4f6af1b1053.gif" border="0" alt="NN.GIF" width="74" height="19" /> as a loss of phase lock and be forced to reestimate the net integer ambiguity.</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">Therefore the phase corrections broadcast by the base should be calculated as</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="f77eaa080fbb7f5ce1e72ed7f52104bd.gif" border="0" alt="0280-02.GIF" width="396" height="32" /></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">Based on the above discussion, the integer value of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> does not affect the positioning accuracy at the roving receivers, but the value of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> must be constant (during a given satellite fly-over). The integer value of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> can, for example, be selected so that the </font><font face="Symbol" size="3">D<i>f</i></font><font face="Times New Roman, Times, Serif" size="3">(<i>t</i>)</font><font face="Times New Roman, Times, Serif" size="1"><sub>DGPS</sub></font><font face="Times New Roman, Times, Serif" size="3"></font><font face="Symbol" size="3">禄</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>DGPS</sub></font><font face="Times New Roman, Times, Serif" size="3">(<i>t</i>) at the initial time that </font><font face="Symbol" size="3">D<i>f</i></font><font face="Times New Roman, Times, Serif" size="3">(<i>t</i>)</font><font face="Times New Roman, Times, Serif" size="1"><sub>DGPS</sub></font><font face="Times New Roman, Times, Serif" size="3"> is broadcast.</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">Note that the value of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> in Eq. (7.85) is distinct from the variable <img src="cd72d36d8924060834c8f78c59935613.gif" border="0" alt="NCIRC.GIF" width="13" height="14" /> that is estimated in either Sec. 7.5.3 or 7.5.4. The value of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> (for each satellite) can be arbitrarily assigned to any integer, since a compensating integer is estimated (per satellite) by the rover. The value of <img src="cd72d36d8924060834c8f78c59935613.gif" border="0" alt="NCIRC.GIF" width="13" height="14" /> is the correct integer for which the phase and code measurements are consistent with all error sources modeled. As Figs. 7.17 and 7.23 show, correct estimation of <i>N</i> requires significant delay from the time of initial phase measurement. Therefore the arbitrary (constant integer) specification of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> described above is usually preferred. This fixing of <img src="41cda95f2e908eec694d60141f22bada.gif" border="0" alt="NCIRCO.GIF" width="18" height="20" /> should not be interpreted as knowledge of <i>N</i>. If the <i>erroneous</i> assignment <img src="e01f43cb60dc51c5bb5838461ad5bacc.gif" border="0" alt="C0280-01.GIF" width="48" height="20" /> were made in the pseudorange corrections, then an arbitrary per-satellite bias would be introduced that would affect the rover positioning accuracy.</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="17"></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">7.6<br />Attitude Determination</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 shown in Sec. 6.8, the INS error state, including three augmented states each for accelerometer and gyro errors, is not completely observable during initialization or periods of relatively benign dynamics. Under such conditions, the accuracy in certain directions of the error space will deteriorate. Several researchers have suggested the use of multiple GPS antennas and carrier-phase observations for attitude determination. Usually these techniques are described</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_279.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_280</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_281.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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