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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_165</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_164.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_165</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_166.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 165</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">be significantly magnified, as shown in Eqs. (5.57) and (5.58). However, if the frequency separation were too large, then separate antennas would be required to receive the two signals.</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">5.7<br />Carrier-Phase Observables</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 addition to tracking the code-based pseudorange, a receiver in phase lock to the carrier signal is able to track the relative phase shift in the carrier between any two time instants. Therefore, although the receiver cannot directly measure the number of carrier cycles between it and a given satellite, the receiver can measure the change in this number of cycles. The carrier-phase measurement can be used in various ways to aid in the navigation problem.</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 carrier-phase observable for the <i>i</i>-th satellite can be represented 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="55c155586f453d91330c87807f6b70a9.gif" border="0" alt="0165-01.GIF" width="435" height="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"><img src="b08df589de3f7491a2608eb00cea0e20.gif" border="0" alt="0165-02.GIF" width="354" height="21" /></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="f7bda0addc2a325256d436a2677d1ee7.gif" border="0" alt="C0165-01.GIF" width="35" height="26" /> is the measured carrier phase, <i>N</i></font><font face="Times New Roman, Times, Serif" size="2"><sup>(<i>i</i>)</sup></font><font face="Times New Roman, Times, Serif" size="3"> is the integer phase ambiguity, </font><font face="Symbol" size="3">l</font><font face="Times New Roman, Times, Serif" size="3"> is the carrier wavelength, mp</font><font face="Times New Roman, Times, Serif" size="2"><sup>(<i>i</i>)</sup></font><font face="Times New Roman, Times, Serif" size="3"> is the carrier-signal multipath, </font><font face="Symbol" size="3"><i>b</i></font><font face="Times New Roman, Times, Serif" size="2"><sup>(<i>i</i>)</sup></font><font face="Times New Roman, Times, Serif" size="3"> is random measurement noise, and all other symbols are as defined in Eq. (5.1). The interest in the carrier signal stems from the fact that the noncommon-mode errors mp</font><font face="Times New Roman, Times, Serif" size="2"><sup>(<i>i</i>)</sup></font><font face="Times New Roman, Times, Serif" size="3"> and </font><font face="Symbol" size="3"><i>b</i></font><font face="Times New Roman, Times, Serif" size="2"><sup>(<i>i</i>)</sup></font><font face="Times New Roman, Times, Serif" size="3"> are approximately 100 times smaller that the respective errors on the code observable. The common-mode errors are essentially the same as those on the code observable, except that the ionospheric error enters Eqs. (5.1) and (5.59) with opposite signs. In the differential mode of operation (see Sec. 5.8), the common-mode errors can be reduced to produce an observable accurate to a few centimeters. Let this differentially corrected phase be described 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="bc40e183dc1b09de1a700cbda48afd06.gif" border="0" alt="0165-03.GIF" width="465" 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"><img src="9d5c856a313a7ba30aad97be85cc5ce2.gif" border="0" alt="0165-04.GIF" width="423" height="24" /></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 subscript in <img src="795e68d617642ef4236226109fdcfcc2.gif" border="0" alt="C0165-02.GIF" width="47" height="29" /> refers the generic quantity </font><font face="Symbol" size="3">z</font><font face="Times New Roman, Times, Serif" size="3"> to the DGPS base station. The differentially corrected phase of Eq. (5.62) provides a very accurate measure of range, if the integer ambiguity can be determined.</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 integer phase ambiguity is the whole number of carrier-phase cycles between the receiver and the satellite at an initial measurement time. It is a (usually large) unknown integer constant (barring cycle slips). To make use of a carrier-phase observable as a range estimate, the integer ambiguity must be estimated (see Sec. 5.7.3). Alternatively, the carrier-phase measurement could be differenced across time epochs, eliminating the constant integer offset, to provide an accurate measurement of the change in range, as described in Sec. 5.7.1.</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_164.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_165</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_166.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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