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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_185</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_184.html">< previous page</a></td> <td id="ebook_previous" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_185</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_186.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 185</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">sources of measurement noise. Also, in Table 5.8, </font><font face="Symbol" size="3"><i>s</i></font><font face="Symbol" size="1"><sub>r</sub></font><font face="Times New Roman, Times, Serif" size="3"> indicates the standard deviation of the noncommon-mode range noise. The formulas in the last column are valid for either code or carrier differential operation.</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">5.9<br />DGPS Implementation Protocol</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 implementation of a DGPS system requires at least two receivers and a means to communicate the corrections from the base to the rover in a timely fashion [10, 44, 158]. As an alternative to implementing a private DGPS system, corrections can be purchased from commercial services and are currently available in some locations through government agencies such as the U.S. Coast Guard [126].</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">Since uniformity of DGPS service across providers will simplify distribution and acceptance, the Radio Technical Marine Service has defined standards for the implementation and message format of DGPS services. This protocol is described in Ref. 127. According to the RTCM-104 standard, the broadcast corrections should have the form of Eq. (5.99) [corrected for receiver clock, <i>c</i></font><font face="Symbol" size="3">D</font><font face="Times New Roman, Times, Serif" size="3"><i>t</i></font><font face="Times New Roman, Times, Serif" size="1"><sub>sv</sub></font><font face="Times New Roman, Times, Serif" size="3">(<i>t</i>), and multipath, but not for <i>c</i></font><font face="Symbol" size="3">D</font><font face="Times New Roman, Times, Serif" size="3"><i>t</i></font><i><font face="Times New Roman, Times, Serif" size="1"><sub>a</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>t</i>)]. To accommodate latencies between the time of calculation and the time of use, the RTCM-104 correction takes the form of a first-order polynomial</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="40cbcd0933853eb8adfd8ad22e40542e.gif" border="0" alt="0185-01.GIF" width="367" height="42" /></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>t</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 a reference time defined by the base, corr(<i>t</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">) and <img src="4ce70c16978e6eb10ded9a2d802b7946.gif" border="0" alt="C0185-01.GIF" width="86" height="31" /> are the values of the correction and correction rate both valid at time <i>t</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">, and <i>t</i> is the time at which the correction will be applied. See Ref. 127 for a description of the exact message formats.</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">Before using a correction of the form in Eq. (5.104), it is natural to ask whether improved compensation for the latency in the differential correction could be attained through the use of an optimal estimator. Implementation of such an estimator requires a suitable state-space model for the differential corrections. Such a model is derived and evaluated relative to a linear polynomial predictor in Ref. 42. The linear prediction equation is shown to have performance statistically equivalent to that of the optimal predictor.</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">5.10<br />GPS Summary</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 GPS system is a worldwide asset that is provided by the U.S. government and available to the user at the cost of a receiver. The uniform worldwide accuracy and high reliability of the system are motivations for the use of GPS in numerous applications. Many such applications are described in Ref. 101.</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 range accuracies for four GPS operating examples are presented in Table 5.9. Position standard deviations can be calculated from the range accuracies in the table based on assumed PDOP values as described in Sec. 5.5. The standard deviations in the table are based on the error standard deviations presented</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_184.html">< previous page</a></td> <td id="ebook_next" align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_185</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_186.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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