report of the action team on global navigation satellite systems (gnss)

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35. The GPS baseline system is comprised <strong>of</strong> three segments, whose purpose is to provide areliable and continuous positioning and timing service to <strong>the</strong> GPS user community. These threesegments are known as <strong>the</strong> Space Segment, Control Segment and User Segment.36. The User Segment is comprised <strong>of</strong> receivers from a wide variety <strong>of</strong> United States andinternational agencies, in addition to <strong>the</strong> growing private user base. The GPS space segmentconsists nominally <strong>of</strong> a constellation <strong>of</strong> 24 operational Block II satellites (Block II, IIA and IIR).37. Each satellite broadcasts a navigation message based upon data periodically uploadedfrom <strong>the</strong> Control Segment and adds <strong>the</strong> message to a 1.023 MHz Pseudo Random Noise (PRN)Coarse/Acquisition (C/A) code sequence. The satellite modulates <strong>the</strong> resulting code sequenceonto a 1575.42 MHz L-band carrier to create a spread spectrum ranging signal, which it <strong>the</strong>nbroadcasts to <strong>the</strong> user community. This broadcast is referred to in this Performance Standard as<strong>the</strong> SPS ranging signal.38. Each C/A code is unique and provides <strong>the</strong> mechanism to identify each satellite in <strong>the</strong>constellation. A block diagram illustrating <strong>the</strong> Block IIA satellite's SPS ranging signal generationprocess is provided in Figure 1-1. The GPS satellite also transmits a second ranging signal knownas L2, that supports PPS user two-frequency corrections. L2, like L1, is a spread spectrum signaland is transmitted at 1227.6 MHz.Figure 1-1. Block IIA SPS Ranging Signal Generation and Transmission10
Service Availability Standard39. The United States Government commits to maintaining <strong>the</strong> Position Dilution <strong>of</strong> Precision(PDOP) in accordance with <strong>the</strong> following tolerances.Table 1-2. Position Dilution <strong>of</strong> Precision Availability StandardPDOP Availability Standard≥ 98% global Position Dilution <strong>of</strong>Precision (PDOP) <strong>of</strong> 6 or less.≥ 88% worst site PDOP <strong>of</strong> 6 or less.Conditions and Constraints• Defined for position solution meeting<strong>the</strong> representative user conditions andoperating within <strong>the</strong> service volumeover any 24-hour interval.• Based on using only satellitestransmitting standard code andindicating “healthy” in <strong>the</strong> broadcastnavigation message (sub-frame 1).40. In support <strong>of</strong> <strong>the</strong> service availability standard, 24 operational satellites must be availableon orbit with 0.95 probability (averaged over any day). At least 21 satellites in <strong>the</strong> 24 nominalplane/slot positions must be set healthy and transmitting a navigation signal with 0.98 probability(yearly averaged).41. The United States Government’s commitments for maintaining PDOP (Table 1-2) andconstellation SPS SIS URE (see Section on Service Reliability Standard) result in support for aservice availability standard as presented in Table 1-3.11
Page 1 and 2: REPORT OF THE ACTION TEAM ONGLOBAL
Page 3 and 4: This document has not been formally
Page 5 and 6: CONTENTSIntroduction ..............
Page 7 and 8: REPORT OF THE ACTION TEAMON GLOBAL
Page 9 and 10: Product4. The product of</s
Page 11 and 12: II.OVERVIEW OF PLANNED AND EXISTING
Page 13 and 14: virtually every facet of</s
Page 15: 27. Time and frequency disseminatio
Page 19 and 20: Table 1-4. Service Reliability Stan
Page 21 and 22: 50. The GPS Control Segment (CS) is
Page 23 and 24: Service Availability Standard62. Th
Page 25 and 26: 71. The GPS Navigation Message cons
Page 27 and 28: the Board, mainly
Page 29 and 30: • Vertical :• Velocity:• User
Page 31 and 32: • The network of
Page 33 and 34: 126. The EU and ESA have concluded
Page 35 and 36: • The Search and Rescue Service (
Page 37 and 38: invitation to tender to this effect
Page 39 and 40: 2. EGNOS169. As previously mentione
Page 41 and 42: 183. Three phases have been identif
Page 43 and 44: an air navigation service dedicated
Page 45 and 46: • Aviation: a representative desi
Page 47 and 48: 222. The information is openly avai
Page 49 and 50: 234. The United Nations Office for
Page 51 and 52: • Provide consultancy and advice
Page 53 and 54: 255. Methods to compare distant clo
Page 55 and 56: measurements are used to evaluate <
Page 57 and 58: market can begin to develop. That a
Page 59 and 60: Nations and voluntary contributions
Page 61 and 62: IV.GNSS APPLICATIONSA. General appl
Page 63 and 64: 317. Agricultural applications incl
Page 65 and 66: 326. The regional activity in <stro
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GNSS SBAS-WAAS trials in th
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356. Other activit
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with respect to the</strong
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379. Argentina has at present a “
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Brazilian Continuous GPS Network (R
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all mapping-related works in <stron
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monitoring, national reference <str
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Programs: B.Sc/M.Sc/Ph.D. in geomat
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• University of
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V. NEEDS AND CONCERNS OF DEVELOPING
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Surveying, Mapping, Land Use• Pre
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include Special Implementation Proj
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VI.EXISTING TRAINING OPPORTUNITIES
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465. Many other GN
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• Theory and practice of<
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D. GNSS training opportunities <str
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VII.INSTITUTIONAL MODELS FOR INTERN
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Environment Programme (UNEP), and <
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appropriate national security reaso
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VIII.RECOMMENDATIONS541. A number <
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for Outer Space Affairs, developmen
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• Develop the sk
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Recommendation 2. The development <
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583. The need to develop th
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589. Project 2:Pilot Projects (4 pr
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Annex I: Indian universities, resea
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University/researchinstitute/compan
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Annex III: Italian universities and
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Annex IV: Italian non-governmental
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Annex IV: Italian non-governmental
Page 127 and 128:
APPENDIXList of we
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report of the action team on global navigation satellite systems (gnss)

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