Of each outage two of which have positive sense and

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Unformatted text preview: . In this way the receiver is able to track eight satellites with only six channels. An interesting behavior occurred after the receiver reacquired the signal following the outage: the PRN was removed from the position solution set and reassigned to the multiplexing sixth channel. This continued for a period of five minutes before the PRN was returned to the position solution set. The behavior of a 12-channel, single-frequency receiver was observed for the outage that occurred on PRN 15 on November 26, 1998. Figure A-4-4 shows C/NO values for the channel tracking PRN 15. At the time of the three outages, the channel substituted PRN 31 to be tracked, then returned quickly (44 seconds for the first outage, 8 seconds for the second, and 16 seconds for the third) to track PRN 15. Page A-22 October 2001 GPS SPS Performance Standard Receivers A & B – November 26, 1998 PRN 15 Range Acceleration Error (m/s2) vs. GPS Time of Week (s) 4 Denver Rcvr B 2 0 -2 -4 350300 350350 350400 350450 350500 350550 350600 4 Atlantic City Rcvr B 2 0 -2 -4 350300 350350 350400 350450 350500 350550 350600 4 Arcata Valley Rcvr A 2 0 -2 -4 350300 350350 350400 350450 350500 350550 350600 Figure A-4-2. Dual-Frequency Receiver Response (PRN 15 Anomaly) Receiver C (single frequency, six channel) PRN 19 C/N0 November 2, 1998 16 14 12 Multitasking on sixth channel 10 8 Six second outage occurs at 3:07:38 6 4 2 0 3:07:00 3:07:10 3:07:20 3:07:30 3:07:40 3:07:50 3:08:00 3:08:10 3:08:20 3:08:30 3:08:40 3:08:50 3:09:00 3:09:10 Figure A-4-3. Single-Frequency, 6-Channel Receiver Response (PRN19 Anomaly) Page A-23 October 2001 GPS SPS Performance Standard Receiver D (single freq) PRN 15 C/N0 60 50 November 26, 1998 Outage 1 Start time: 1:20:13 Duration:44 sec 40 Outage 3 Start time: 1:24:43 Duration:16 sec 30 20 Outage 2 Start time: 1:23:31 Duration:8 sec 10 0 1:19:00 1:20:00 1:21:00 1:22:00 1:23:00 1:24:00 1:25:00 1:26:00 1:27:00 Figure A-4-4. Single-Frequency, 12-Channel Receiver Response (PRN 15 Anomaly) Page A-24 October 2001 GPS SPS Performance Standard SECTION A-5 Accuracy Characteristics GPS SPS accuracy has improved tremendously since the use of Selective Availability (SA) was terminated. This section provides some insight into current accuracy characteristics in the absence of SA. Since the new SPS standards focus on Signal-in-Space (SIS) performance, initial discussions are framed in like manner. The discussion begins with an assessment of SIS SPS accuracy as a function of geographic location. Performance with combinations of two satellites removed is then discussed. SIS SPS positioning accuracy for the month of June 2000 is presented to illustrate observed daily performance variations. The section continues with a discussion of SIS time transfer performance. The purpose of standards is to establish levels of performance against which a service provider will commit to operating a service. The SIS basis of the GPS SPS standards makes it a straightforward proposition to mana...
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This document was uploaded on 09/26/2013.

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