SBAS广域增强系统
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图23 广域增强系统WAAS的二维平面定位性能054Satellite classroom 卫星课堂GPS系统的关键性能分析―――下之二第十七讲7 广域增强系统(WAAS)性能简介广域增强系统完好性风险定义为系统估算的载体的位置值超过水平告警门限HAL(Horizontal Alert Limits)或者垂直告警门限VAL(Vertical Alert Limits)时,卫星导航系统在规定的告警时间(time-to-alarm)内没有告警的概率。
另一方面,连续性风险定义为在系统工作过程中,系统告警能够省略的概率。
广域增强系统W A A S 的最低运行控制性能标准MOPS(Minimum OperationalPerformance Standards)定义为,差分修正的导航解在垂直保护门限VPL(Vertical Protection Level)以及水平保护门+ 刘天雄图24 广域增强系统WAAS的垂直定位性能限HPL(Horizontal Protection Level)范围内概率的必须满足99.99999%。
因此,误差的真值(true error)在107 秒内超过保护限的次数不能多于一次。
如果计算的保护限超过了相应的告警门限,那么系统将告警,测量的数据不能用于定位。
如果系统在运行过程中发出了告警信息,必须推导告警信息处理算法,否则系统在整个周期内将被宣布不可用。
美国斯坦福大学(Stanford University)在位于美国加利福尼亚州斯坦福的国家卫星测试床NSTB(National Satellite Test Bed),开展了对静态用户开展了广域增强系统W A A S的二维平面定位性能评估测试,测试结果如图23所示,直方图中横坐标为广域增强系统W A A S给出的位置已被标定的天线的位置测量值和实际位置之间的误差,纵坐标为不同导航解下计算得到的保护门限。
图22中HMI表示“危险的错误引导信息(Hazardously Misleading Information)”,MI表示“错误引导信息(Misleading Information)”。
卫星导航差分系统和增强系统(十)+刘天雄3.4.1 美国广域增强系统WAAS3.4.1.1 系统组成广域增强系统(Wide Area Augmentation System,WAAS)是美国的星基增强系统,是为满足美国民用航空对GPS更高的精度和完好性要求,1992年,美国联邦航空管理局(FAA)在WADGPS的基础上设计的。
其利用GEO地球同步静止轨道卫星广播GPS差分修正数据和完好性信息电文,实现在北美地区GPS系统的完好性增强。
WAAS系统的GEO卫星不仅作为完好性告警通道,播发增强信号的同时还提供测距服务,利用GEO卫星覆盖范围大且位置相对稳定的特点,对地面用户高仰角高,作为一个稳定的测距信号源,可补充GPS星座用户可见卫星数量。
WAAS系统的发展经历了四个阶段,一是初始运行阶段(Initial Operating Capability,IOC),2003年已实现目标,2003年7月10日,FAA宣布WAAS系统为民航提供服务,服务范围覆盖美国本土95%的区域以及阿拉斯加部分区域。
二是全面实现带垂直引导的水平进近LPV服务(Full LPV Performance),2008年已实现目标,2007年服务区域扩展到加拿大和墨西哥。
三是全面实现带垂直引导的水平进近LPV-200服务(Full LPV-200 Performance),2014年8月,WAAS系统可为全美提供LPV-200服务。
四是开展双频多系统(dual-frequency multi-constellation,DFMC)兼容互操作研究,进一步提升WAAS系统的可用性,计划在2014年~2028年期间实现DFMC 服务。
目前,WAAS系统支持民航航路、终端、进近以及带垂直引导的水平进近(Localizer Performance with Vertical,LPV)服务,为美国和加拿大一千多个机场提供仪表垂直引导进近(vertically guided instrument approach)服务,即带垂直引导的水平进近LPV-200服务(接近CAT-I进近水平),可以引导飞机从200英尺的高度着陆(height above touchdown,HAT)。
SBAS 即Space Based Augmentation System,是利用地球静止轨道卫星建立的地区性广域差分增强系统。
目前全球发展的SBAS系统有:欧空局接收卫星导航系统(EGNOS),欧洲大陆美国雷声公司的广域增强系统(W AAS),美洲大陆日本的多功能卫星增强系统(MSAS),亚洲大陆三者具有完全兼容的互操作性。
其特点是:1、通过地球静止卫星(GEO)发布包括GPS卫星星历误差改正、卫星钟差改正和电离层改的信息;2、通过GEO卫星发播GPS和GEO卫星完整的数据;3、GEO卫星的导航载荷发射GPS L1测距信号。
SBAS覆盖图WAAS 这个名词、全名为Wide Area Augmentation System,即广域增强系统。
WAAS是美国联邦航空局(FAA)及美国交通部为提升飞行精确度而发展出来的,因为目前单独使用GPS 并无法达到联邦航空局针对精确飞行导航所设定的要求。
WAAS 包含了约25个地面参考站台,位置散布于美国境内,负责监控GPS 卫星的资料。
其中两个分别位于美国东西岸的主站台搜集其它站台传来的资料,并据此计算出GPS 卫星的轨道偏移量、电子钟误差,以及由大气层及电离层所造成的讯息延迟时间,汇整后经由两颗位在赤道上空之同步卫星的其中之一传播出去。
此W AAS 讯号的发送频率与GPS 讯号的频率相同,因此任何具备WAAS 功能的GPS 机台都可接收此讯号,并藉此修正定位信息。
WAAS 可以校正由电离层干扰、时序控制不正确以及卫星轨道错误等因素所造成的GPS 讯号误差,也能提供各卫星是否正常运转之信息。
虽然W AAS 目前尚未正式通过美国航空局的飞行使用认证,但此系统已开放给一般民众使用,例如从事航海或其它休闲活动的人们。
W AAS提供校正GPS讯号的功能,让您得到更精确的定位。
到底能提升多少精确度呢?官方给出的数据是,可以平均提升最多五倍的精确度!目前无W AAS功能的普通GPS接收机的正常精确度是15米,而一台具备W AAS功能的GPS接收机能在95%的情况下提供您误差小于三公尺的精准定位,而且您不必为了使用WAAS功能而支付任何使用费。
国际星基增强系统综述邵搏;耿永超;丁群;吴显兵【摘要】由于单频技术体制的制约,现有星基增强系统均为到达一类精密进近性能指标的要求.为了满足航空用户对星基增强系统在精度、完好性、连续性和可用性上的要求,目前全球的星基增强系统都在开展由单频单系统向双频多系统的过渡,并成立了相应的工作组来制定双频多系统星基增强系统的定义文档和空间信号接口文档.同时,各星基增强系统也在着手准备地面系统的升级工作,计划在2020年前后提供初步的双频星基增强服务.我国为了推进北斗星基增强系统的国际化进程,已经启动了频率国际协调工作和国际化标准制定工作.【期刊名称】《现代导航》【年(卷),期】2017(008)003【总页数】5页(P157-161)【关键词】SBAS;WAAS;EGNOS;MSAS;GAGAN;SDCM;KASS;BDSBAS【作者】邵搏;耿永超;丁群;吴显兵【作者单位】中国电子科技集团公司第二十研究所,西安 710068;中国电子科技集团公司第二十研究所,西安 710068;中国电子科技集团公司第二十研究所,西安710068;中国电子科技集团公司第二十研究所,西安 710068【正文语种】中文【中图分类】TN96.1全球导航卫星系统(GNSS)作为主要导航手段,已经进入了快速发展和应用阶段。
为了提升GNSS系统的性能,需要相应增强系统满足不同用户对高完好性和高精度的需求。
星基增强系统(SBAS)能够满足从航路、终端区到一类精密进近(CAT-I)各阶段的导航需求。
由大量分布广泛的监测站(位置已知)对导航卫星进行监测,由地球同步卫星(GEO)向用户播发改正数信息(星历误差、卫星钟差、电离层延迟)和完好性信息(用户差分距离误差、格网电离层垂直误差),实现对卫星导航系统定位精度的改进和完好性性能的提高。
星基增强系统构成包括空间段、地面段和用户段三部分。
空间段是由GEO卫星构成;地面段包括监测站、主控站、注入站和通信网络;用户段是由能够接收SBAS 信号的设备构成。
美国星基增强系统发展现状和未来张彦东【摘要】本文介绍了星基增强系统产生的背景以及美国的星基增强系统WAAS (广域增强系统)的系统架构,回顾了WAAS(广域增强系统)的发展历史,分析了WAAS(广域增强系统)的发展现状和未来的发展方向。
%This article introduces the background of the U.S. Satellite Based Augmentation System (SBAS) and the system architecture of SBAS WAAS (Wide Area Augmentation System), reviews the development process of WAAS and makes analysis about the current situation and future development of WAAS.【期刊名称】《现代导航》【年(卷),期】2014(000)005【总页数】4页(P379-382)【关键词】GPS;国际民航组织;星基增强系统;广域增强系统【作者】张彦东【作者单位】民航内蒙古地区空中交通管理局,呼和浩特 010070【正文语种】中文【中图分类】V2491 星基增强系统1.1 星基增强系统产生的背景GPS系统自建成以来到现在,其标准定位服务(Standard Positioning Service — SPS)可以向民用用户提供水平方向100m左右,垂直方向150m左右的定位精度,但随着应用领域的不断拓展,民用航空对于 GPS的应用提出了更加苛刻的要求,即GPS必须满足包括精度、完好性、连续性和可用性在内的全方位性能要求。
为了使卫星导航系统能够应用于民用航空领域,必须保证系统的性能达到如表1中所提出的相应要求。
根据霍普金斯大学对于GPS性能进行的评估,30颗GPS卫星,在取消SA并且同时使用双频接收机的情况下,所提供的导航服务性能仅仅能满足远洋航路的要求。
基于SBAS的高精度定位技术研究随着各种立体导航技术的快速发展,高精度定位技术越来越受到人们的关注。
其中基于SBAS的高精度定位技术是目前应用广泛的一种,下面就针对该技术进行一些探讨和研究。
一、背景SBAS即卫星基准层增强系统,是美国导航卫星系统(GPS)局研制的一种增强卫星导航系统。
该系统主要采用差分GPS技术,通过在地面上布设若干个接收机,监测GPS信号在其上的误差,得到一个带有误差信息的参考坐标,以此来校正卫星和接收机之间的距离误差,从而提高GPS定位的精度。
二、SBAS的工作原理SBAS系统由地面监测站、数据处理系统和同步星座组成。
地面监测站通过监测GPS信号在其上的误差,得到参考坐标并上传至SBAS数据中心;数据中心将参考坐标进行差分计算,得到距离误差数据,然后将校正信息经同步卫星传输至用户终端,最后在接收机端通过将校正信息与GPS信号内置的精度信息相结合,获得高精度的定位信息。
三、SBAS技术的应用SBAS技术被广泛应用于航空领域,如民航、商飞、军航等。
在航空领域,精准的定位信息对于飞行安全至关重要,因此SBAS 技术在飞行导航、地面降落导航等方面都具有重要的作用。
此外,SBAS技术还可以应用于海洋、铁路、道路等领域的定位和导航。
四、SBAS技术的优势和局限SBAS技术相对于其他GPS增强技术,具有以下优势:1、SBAS系统具有全天候、全球性的覆盖范围,可为用户提供可靠的定位和导航服务。
2、SBAS系统具有高精度、高稳定性的特点,能够提供厘米级的定位精度,满足各种高精度定位需求。
3、SBAS系统的成本较低,适合于广泛的应用场景。
不过,SBAS技术目前仍然存在以下局限:1、SBAS系统的天线需要能够看到至少4颗GPS卫星,因此在深度山区、城市峡谷等环境下会受到影响。
2、SBAS系统的运维成本较高,需要不断维护和升级。
3、SBAS系统的建设和运营需要多个国家和地区的合作,因此易受到政治因素的影响。
satellite based augmentation system -回复什么是卫星增强系统(satellite-based augmentation system)?卫星增强系统(SBAS)是一种通过卫星信号来提供精确的位置和导航信息的技术。
它是全球卫星导航系统(如GPS、GLONASS、北斗导航系统)的一种增强系统,旨在提高位置和导航服务的准确性、可靠性和可用性。
SBAS系统通常由地面控制站和一组地球轨道上的卫星组成。
地面控制站负责监测全球导航系统卫星的轨道和时间偏差,并计算位置和时间修正数据。
这些修正数据通过卫星传输到用户的接收设备,从而实现对全球导航系统信号的增强。
SBAS系统是通过提供信号纠正来提高定位和导航准确性的。
全球导航系统信号在传输过程中可能会受到大气层和其他因素的影响,从而导致位置和时间的偏差。
SBAS系统通过纠正这些误差来提供更精确的位置和导航信息。
SBAS系统的工作原理如下:地面控制站监测全球导航系统卫星信号,计算出卫星的轨道和时间修正数据。
这些数据被发送到地球轨道上的一组地球轨道上的卫星,然后由这些卫星发送回地球,传输给用户接收设备。
用户接收设备接收到这些数据后,使用它们来纠正全球导航系统信号并提供更准确的位置和导航信息。
SBAS系统的优势在于提供了高精度的位置和导航信息。
它可以在各种应用领域中发挥作用,包括航空、航海、车辆导航和物流等。
在航空领域,SBAS系统可以提供更准确的飞行引导和自动驾驶功能,提高航班安全性和效率。
在航海领域,SBAS系统可以帮助船舶精确定位,避免与其他船只和障碍物的碰撞。
在车辆导航和物流领域,SBAS系统可以提供准确的行驶路径和交通信息,提高物流运输的效率。
SBAS系统的发展和应用是一个持续的过程。
目前,美国的广域增强系统(WAAS)和欧洲的欧洲地区增强系统(EGNOS)是两个较成熟和广泛应用的SBAS系统。
其他国家和地区也在开发和部署自己的SBAS系统。
Number:CTSO-C145eApproved by:Xu ChaoqunChina Civil Aviation Technical Standard OrderAirborne Navigation Sensors Using The Global Positioning SystemAugmented By The Satellite Based Augmentation System (SBAS)1. Purpose.This China Civil Aviation Technical Standard Order (CTSO) is for manufacturers applying for airborne navigation sensors using the global positioning system (GPS) augmented by the satellite based augmentation system (SBAS) CTSO authorization (CTSOA). This CTSO prescribes the minimum performance standards(MPS) that airborne navigation sensors using the GPS augmented by the SBAS must first meet for approval and identification with the applicable CTSO marking.2. Applicability.This CTSO affects new application submitted after its effective date.Major design changes to article approved under this CTSO will require a new authorization in accordance with section 21.353 of CCAR-21R4.3. RequirementsNew models of airborne navigation sensors using the GPS augmented by the SBAS identified and manufactured on or after the effective date of this CTSO must meet the MPS qualification and documentation requirements for functional equipment Class Beta in RTCA, Inc. document RTCA/DO-229E, Minimum Operational Performance Standards for Global Positioning System/Satellite-Based Augmentation System Airborne Equipment dated December 15, 2016, Section 2.1. Class Beta equipment is defined in RTCA/DO-229E, Section 1.4 and Appendix 2 adds a new section 1.8.3.Note: Manufacturers have the option to use the RTCA/DO-229E change described in Appendix 3. The change is based on a past commonly granted deviation.a. An alternate method for applicants is to apply for CTSO-C145e using their existing approved design data plus additional substantiation data showing compliance with the changes in RTCA/DO-229E. The three areas where requirements changed are: 1) expanding the SBAS pseudorandom noise (PRN) codes (i.e., PRN range of 120 thru 158); 2) ensuring a graceful degradation to GPS-only operations; and, 3) prohibiting use of the broadcast Navigation Message Correction Table.Note 1: It is not necessary for applicants to re-submit previously approved deviations. Previously approved deviations, and any limitations,will apply to the CTSO-C145e CTSOA.Note 2: Applicants with Class 1 and 2, revision ‘b’ equipment must not have claimed the 3db broadband intrasystem noise credit.b. CTSO-C145e applicants have the option to use a CTSO-C204a SBAS CCA functional sensor. Applicants choosing to use a CTSO-C204a SBAS CCA can take certification compliance credit by virtue of the CTSO-C204a CTSOA for:z Meeting the MPS section 2.1 requirements;z The hardware/software qualification;z The failure condition classification; and,z MPS section 2.5 performance testing (functional qualification) except those specified in Appendix 1 of this CTSO.c. The CTSO-C145e applicant using a CTSO-C204a SBAS CCA functional sensor shall perform the testing described in Appendix 1 and satisfy the remaining paragraphs in this CTSO not covered by the bullets above to receive a CTSO-C145e CTSOA.Note: The end-use manufacturer using a CTSO-C204a SBAS CCA functional sensor as part of their CTSO-C145e application assumes full responsibility for the design and function under their CTSO-C145e authorization.d. Functionality.This CTSO’s standards apply to equipment intended to provideposition, velocity, time information for a navigation management unit application that outputs deviation commands keyed to a desired flight path, or a non-navigation application such as automatic dependent surveillance-broadcast (ADS-B) or terrain awareness and warning system (TAWS). In navigation applications, pilots or autopilots will use the deviations output by the navigation management unit to guide the aircraft. In non-navigation applications, the position, velocity, time outputs will provide the necessary input for the end-use equipment. These TSO standards do not address integration issues with other avionics.e. Failure Condition Classifications.(1) Failure of the function defined in paragraph 3.d resulting in misleading information for en route, terminal, approach lateral navigation (LNA V), and approach LNA V/vertical navigation (VNA V) position data is a Major failure condition.(2) Failure of the function defined in paragraph 3.d resulting in misleading information for approach localizer performance without vertical guidance (LP), and approach localizer performance with vertical guidance (LPV) position data is a Hazardous failure condition.(3) Loss of the function defined in paragraph 3.d for enroute through approach LP/LPV position data is a Major failure condition.(4) Design the system to at least these failure condition classifications.f. Functional Qualification.(1) Demonstrate the required functional performance under the test conditions specified in RTCA/DO-229E, Section 2.5, or(2) When using a CTSO-C204a SBAS CCA functional sensor, demonstrate the required performance under the test conditions in appendix 1 of this CTSO.g. Environmental Qualification.Demonstrate the required performance under the test conditions specified in RTCA/DO-229E, Section 2.4 using standard environmental conditions and test procedures appropriate for airborne equipment. RTCA/DO-229E requires the use of RTCA/DO-160E, Environmental Conditions and Test Procedures for Airborne Equipment, dated December 9, 2004, Sections 4.0 through 8.0 and 10.0 through 25.0. You may use a different standard environmental condition and test procedure than RTCA/DO-160E, provided the standard is appropriate for the SBAS sensor.Note1: The use of RTCA/DO-160D (with Changes 1 and 2 only, incorporated) or earlier versions is generally not considered appropriate and will require substantiation via the deviation process as discussed in paragraph 3.k of this CTSO.Note 2: Applicants using a CTSO-C204a SBAS CCA sensor must perform the environmental qualification with the SBAS CCA in theend-use equipment.h. Software Qualification.If the article includes software, develop the software according to RTCA/DO-178C, Software Considerations in Airborne Systems and Equipment Certification, dated December 13, 2011, including referenced supplements as applicable, to at least the software level consistent with the failure condition classification defined in paragraph 3.e of this CTSO. The applicant may also develop the software according to RTCA/DO-178B, dated December 1, 1992.(2) Applicants using a CTSO-C204a SBAS CCA sensor may use CTSO-C204a as substantiation for the software qualification.i. Electronic Hardware Qualification.If the article includes complex custom airborne electronic hardware, develop the component according to RTCA/DO-254, dated April 19, 2000, Design Assurance Guidance for Airborne Electronic Hardware, to at least the design assurance level consistent with the failure condition classification defined in paragraph 3.e of this CTSO. For custom airborne electronic hardware determined to be simple, RTCA/DO-254, paragraph1.6 applies.(2) Applicants using a CTSO-C204a SBAS CCA sensor may use CTSO-C204a as substantiation for the hardware qualification.j. Barometric-aided Fault Detection and Exclusion (FDE).If the equipment uses barometric-aiding to enhance FDE availability, then the equipment must meet the requirements in RTCA/DO-229E, appendix G.k. Deviations.For using alternative or equivalent means of compliance to the criteria in this CTSO, the applicant must show that the equipment maintains an equivalent level of safety. Apply for a deviation under the provision of 21.368(a) in CCAR-21R4.4. Marking.a. Mark at least one major component permanently and legibly with all the information in 21.423(b) of CCAR-21R4. The marking must include the serial number.b. Also, mark the following permanently and legibly, with at least the manufacturer’s name, subassembly part number, and the CTSO number:(1) Each component that is easily removable (without hand tools); and,(2) Each subassembly of the article that manufacturer determined may be interchangeable.c. If the article includes software and/or airborne electronic hardware, then the article part numbering scheme must identify the software andairborne electronic hardware configuration. The part numbering scheme can use separate, unique part numbers for software, hardware, and airborne electronic hardware.d. The applicant may use electronic part marking to identify software or airborne electronic hardware components by embedding the identification within the hardware component itself (using software) rather than marking it on the equipment nameplate. If electronic marking is used, it must be readily accessible without the use of special tools or equipment.e. At least one major component must be permanently and legibly marked with the operational equipment class (for example, Class 2) as defined in RTCA/DO-229E, Section 1.4.2.5. Application Data Requirements.The applicant must furnish the responsible certification personnel with the related data to support design and production approval. The application data include a statement of conformance as specified in section 21.353(a)(1) in CCAR-21R4 and one copy each of the following technical data:a. A Manual(s) containing the following:(1) Operating instructions and equipment limitations sufficient to describe the equipment’s operational capability.(2) Describe in detail any deviations.(3) Installation procedures and limitations sufficient to ensure that the SBAS sensor, when installed according to the installation or operational procedures, still meets this CTSO’s requirements. Limitations must identify any unique aspects of the installation. The limitations must include a note with the following statement:“This article meets the minimum performance and quality control standards required by a CTSO. Installation of this article requires separate approval.”(4) For each unique configuration of software and airborne electronic hardware, reference the following:(a) Software part number including revision and design assurance level;(b) Airborne electronic hardware part number including revision and design assurance level;(c) Functional description.(5) A summary of the test conditions used for environmental qualifications for each component of the article. For example, a form as described in RTCA/DO-160G, Environmental Conditions and Test Procedures for Airborne Equipment, Appendix A.(6) Schematic drawings, wiring diagrams, and any other documentation necessary for installation of the SBAS sensor.(7) List of replaceable components, by part number, that makes up the SBAS sensor. Include vendor part number cross-references, when applicable.(a) If the equipment can satisfy the requirements of RTCA/DO-229E only when used with a particular antenna, make the use of that antenna (by part number) a requirement on the installation. Include this requirement in the installation manual (IM) as a limitation.(b) If the equipment is installed with a standard antenna, include maximum tolerable currents and voltages into the antenna port. See CTSO-C144a, Passive Airborne Global Navigation Satellite System (GNSS) Antenna, applicable only to operational Class 1 equipment, or CTSO-C190, Active Airborne Global Navigation Satellite System (GNSS) Antenna, applicable to all equipment operational classes.b. Instructions covering periodic maintenance, calibration, and repair, for the continued airworthiness of the SBAS sensor. Include recommended inspection intervals and service life, as appropriate.c. If not using a CTSO-C204a SBAS functional sensor and the article includes software: a plan for software aspects of certification (PSAC), software configuration index, and software accomplishment summary.d. If not using a CTSO-C204a SBAS functional sensor and the article includes simple or complex custom airborne electronic hardware: aplan for hardware aspects of certification (PHAC), hardware verification plan, top-level drawing, and hardware accomplishment summary (or similar document, as applicable).e. A drawing depicting how the article will be marked with the information required by paragraph 4 of this CTSO.f. Adequate specifics on the interface between the SBAS sensor and other systems to ensure proper functioning of the integrated system. If the equipment depends on any external inputs (like baro-aided FDE) to satisfy the requirements of RTCA/DO-229E, make those inputs a requirement in the installation. Include this requirement in the IM as a limitation.g. If the software qualification limits eligibility of the equipment to certain aircraft types, identify the qualification level, and that the equipment is not eligible for all aircraft types. For example, RTCA/DO-178B (or RTCA/DO-178C) Level C software may be associated with a hazardous failure condition for certain aircraft types. Identify other limitations applicable to the failure condition classification, for example, that two installed units are necessary.h. If the equipment has not been demonstrated as compatible with satellite communications (SatCom) record in the limitations section that the equipment should not be installed in SatCom equipped aircraft.i. Identify functionality or performance contained in the article notevaluated under paragraph 3 of this CTSO (that is, non-CTSO functions). Non-CTSO functions are accepted in parallel with the CTSO authorization. For those non-CTSO functions to be accepted, you must declare these functions and include the following information with your CTSO application:(1) Description of the non-CTSO function(s), such as performance specifications, failure condition classifications, software, hardware, and environmental qualification levels. Include a statement confirming that the non-CTSO function(s) do not interfere with the article’s compliance with the requirements of paragraph 3.(2) Installation procedures and limitations sufficient to ensure that the non-CTSO function(s) meets the declared functions and performance specification(s) described in paragraph 5.i.(1).(3) Instructions for continued performance applicable to the non-CTSO function(s) described in paragraph 5.i.(1).(4) Interface requirements and applicable installation test procedures to ensure compliance with the performance data defined in paragraph 5.i.(1).(5) Test plans, analysis and results, as appropriate, to verify that performance of the hosting CTSO article is not affected by the non-CTSO function(s).(6) Test plans, analysis and results, as appropriate, to verify thefunction and performance of the non-CTSO function(s) as described in paragraph 5.i.(1).(7) Alternatively, identify non-CTSO functionality or performance contained in the article not evaluated under paragraph 3 and submit previously accepted data for the non-CTSO function for acceptance in parallel with this CTSO application.j. The quality system description required by section 21.358 of CCAR-21R4, including functional test specifications. The quality system should ensure that it will detect any change to the approved design that could adversely affect compliance with the CTSO MPS, and reject the article accordingly.k. Material and process specifications list.l. List of all drawings and processes (including revision level) that define the article’s design.m. Manufacturer’s CTSO qualification report showing results of testing accomplished according to paragraph 3.f of this CTSO.6. Manufacturer Data Requirements.Besides the data given directly to the authorities, have the following technical data available for review by the authorities:a. Functional qualification specifications for qualifying each production article to ensure compliance with this CTSO.b. Equipment calibration procedures.c. Schematic drawings.d. Wiring diagrams.e. Material and process specifications.f. The results of the environmental qualification tests conducted according to paragraph 3.g of this CTSO.g. If the article includes software, the appropriate documentation defined in the version of RTCA/DO-178 or RTCA/DO-178C specified by paragraph 3.h of this CTSO, including all data supporting the applicable objectives in Annex A, Process Objectives and Outputs by Software Level.h. If the article includes complex custom airborne electronic hardware, the appropriate hardware life cycle data in combination with design assurance level, as defined in RTCA/DO-254, Appendix A, Table A-l. For simple custom airborne electronic hardware, the following data: test cases or procedures, test results, test coverage analysis, tool assessment and qualification data, and configuration management records, including problem reports.i. If not using CTSO-C204a, all the data necessary to evaluate the geo stationary (GEO) satellite bias as defined in RTCA/DO-229E, Section 2.1.4.1.5.j. If the article contains non-CTSO function(s), the applicant mustalso make available items 6.a through 6.h as they pertain to the non-CTSO function(s).7. Furnished Data Requirements.a. If furnishing one or more articles manufactured under this CTSO to one entity (such as an operator or repair station), provide one copy or technical data and information specified in paragraphs 5.a and 5.b of this CTSO. Add any data needed for the proper installation, certification, use, or for continued compliance with the CTSO, of the SBAS sensor.b. If the article contains declared non-CTSO function(s), include one copy of the data in paragraphs 5.i.(1) through 5.i.(4).8. Availability of Referenced Documents.Order RTCA documents from:Radio Technical Commission for Aeronautics, Inc.1150 18th Street NW, Suite 910, Washington D.C. 20036You may also order them online from the RTCA Internet website at: .APPENDIX 1. END-USE EQUIPMENT MANUFACTURER TESTS FOR SBAS CCA FUNCTIONAL POSITION, VELOCITY, TIME (PVT) SENSORS USED FOR NA VIGATION AND NON-NA VIGATION APPLICATIONS1. Scope.This appendix describes the required supplementary equipment level testing, in addition to the environmental testing of RTCA/DO-229E, section 2.4, required by the end-use equipment manufacturer to receive a CTSO-C145e Class Beta authorization when using a CTSO-C204a SBAS CCA functional sensor. These test procedures are intended to streamline and simplify the CTSO-C145e authorization process for the end-use equipment manufacturer by allowing credit for the design and selected testing done at the SBAS CCA functional sensor level. However, the end-use equipment manufacturer retains full responsibility for the design and control of the article per their CTSO-C145e CTSOA.2. General Principles.(a) Testing methods for GPS/SBAS equipment have been standardized by RTCA/DO-229E and serve as the basis for CTSO-C145e. RTCA/DO-229E was written with the perspective of equipment that canbe installed on aircraft. Section 2.4 specifically addresses the issues of the environment in which the equipment operates and provides approved test methods to validate performance in this environment. Section 2.4represents RTCA consensus in identifying which RTCA/DO-229E requirements are sensitive to environmental effects. These requirements are listed in the environmental tables referenced in section 2.4.1.(b) The determination that a MOPS requirement is susceptible to the environment does not depend on whether or not the implementation is a CCA within some host equipment. This is the same concept as an equipment enclosure designed to protect against a benign environment compared to one designed for a severe environment; the identification of susceptible requirements is the same.(c) Therefore this appendix uses the tables of RTCA/DO-229E, section 2.4.1 to identify the MOPS requirements susceptible to environmental affects for an SBAS CCA functional sensor in the end-use equipment. The focus is on the change in environment seen by the SBAS CCA functional sensor as a result of its installation in the end-use equipment. For example, other components inside the end-use equipment may radiate RF energy that could interfere with the GPS functions; therefore the ambient testing done at CCA level is not equivalent to tests done in the end-use equipment. This is the basis for defining the RTCA/DO-229E, section 2.5 performance tests that need to be repeated by the end-use equipment manufacturer.(d) The Class Beta environmental table referenced in RTCA/DO-229E, section 2.4.1 are the prime source to determine theMOPS performance requirements susceptible to environmental conditions. Based on the table, the susceptible requirements can be grouped in two categories: those susceptible to most types of environmental conditions (described in section 3) and those susceptible to just a few (described in section 4).Note: The Tables for Class Beta-1, -2, and -3 equipment identify similar requirements susceptible to the installed environment. The only difference is the applicable MOPS requirements consistent with the operational class (i.e., class -1, - 2, or -3).3. Performance Requirements Susceptible to Most Environmental Conditions.The RTCA/DO-229E requirements for Accuracy (2.1.3.1, 2.1.4.1, and 2.1.5.1) and Sensitivity and Dynamic Range (2.1.1.10) are sensitive to most environmental conditions. However, these requirements are linked to the message loss rate requirement in 2.1.1.3.2. Section 3.1 and 3.2 below identifies the testing end-use equipment manufacturers are required to repeat to demonstrate the SBAS CCA functional sensor continues to meet the Accuracy, Dynamic Range, and Message Loss Rate performance requirements after installation in the end-use equipment. All tests will be run under conditions where the end-use equipment functions are fully enabled to create the worst-case environment.3.1 RTCA/DO-229E, 2.5.8 Accuracy Test.(a) The accuracy test described in section 2.5.8 is actually a joint test covering both accuracy, and sensitivity and dynamic range. This joint testing also applies under environment as stated in section 2.4.1.1.5 with environmental adaptation as described in section 2.4.1.1.1.(b) The demonstration of accuracy is done in accordance with section 2.5.8.1 only for the test case with a broadband external interference noise. This test must be repeated when the CCA is installed in the end-use equipment and it is sufficient to perform it using broadband interference.(1) The environmental testing is limited to broadband interference as it represents the worst case signal to noise condition which is the most sensitive to environmental effects. This applies equally to the environment for the CCA created by the end-use equipment.(2) Section 2.5.8 contains a measurement accuracy test in 2.5.8.1 with the detailed test procedure in 2.5.8.2. The 2.5.8.1 test must be run under the worst case environment identified in the “Additional considerations for internal interference sources” section below. The measurement accuracy testing can be combined with the message loss rate testing in 2.5.2.1.(3) Section 2.5.8.3 is a 24-Hour actual satellite accuracy test. The section 2.5.8.3 test exposes the equipment to a variety of signal conditions and data processing conditions over varying satellite geometrythat will increase confidence that no unforeseen interactions between components within the end-use equipment and the SBAS CCA functional sensor goes undetected. The 24 hr testing in 2.5.8.3 can be combined with the 24 hr message loss rate testing in 2.5.2.4 (see Additional Considerations for Internal Interference Sources section).(4) Section 2.5.8.4 (SBAS Tracking Bias) is an analysis of the GPS hardware and is therefore not necessary to repeat at the end-use equipment level as long as no extra RF components that affect the RF filtering response are inserted in the RF path. Otherwise the end-use equipment manufacturer must repeat the SBAS Tracking Bias test as well.(c) The test threshold is relaxed from 110% to 125% as specified in table 2-25 of the 2.5.8.2.1 test procedure to shorten test time. However, Section 2.5.8 testing (excluding the SBAS Tracking Bias test in 2.5.8.4) for the CCA in the end-use equipment shall be under ambient conditions per section 2.5 with the 110% test pass threshold for maximum test sensitivity.(d) The Section 2.5.8 testing (excluding the SBAS Tracking Bias test in 2.5.8.4) will be repeated against the accuracy requirement consistent with the desired operational class (i.e., 2.1.3.1, 2.1.4.1, and 2.1.5.1 accuracy requirements as appropriate).(e) Only the broadband external interference noise test case usingminimum satellite power will be executed in most cases to shorten test time. Section 2.5.8.1 testing will be repeated for both minimum and maximum satellite power for the worst case environment only.3.2 RTCA/DO-229E, 2.5.2 Message Loss Rate Test.(a) Section 2.5.2 specifies the message loss rate test for the 2.1.1.3.2 message loss rate requirement. This test is conducted in conjunction with the 2.5.8 accuracy testing. Section 2.5.2.2 defines the test procedure to collect data verifying the SBAS message loss rate in the presence of interference using the test cases where the SBAS satellite is at minimum power. Section 2.5.2.3 defines the pass/fail criteria.(b) The test in section 2.5.2.2 will be performed during the measurement accuracy broadband interference test case described in paragraph 3.1.(c) The test procedure in section 2.5.2.4.1 is run in conjunction with the 2.5.8.3 24-hour accuracy test. Section 2.5.2.4.2 defines the pass/fail criteria for the test case described in paragraph 3.1(b)(3).4. Performance Requirements Partially Susceptible to Environmental Conditions.(a) The class Beta tables (tables 2-14, 2-16, and 2-18) in section2.4.1 of RTCA/DO-229E indicates the requirements for Initial Acquisition Time (2.1.1.7) and Satellite Reacquisition Time (2.1.1.9) are sensitive to four environmental conditions: Icing, Lightning InducedTransient Susceptibility, Lightning Direct Effects, and Normal/Abnormal Operating Conditions. The requirements for Loss of Navigation (2.1.1.13.2, 2.1.4.12.2, and 2.1.5.12.2) and Loss of Integrity (2.1.1.13.1, 2.1.4.12.1, and 2.1.5.12.1) are sensitive to low and high operating temperature.(b) The Lightning Induced Transient Susceptibility, Lightning Direct Effects, or Icing environmental conditions are not pertinent to the environment created by the end-use equipment relative to the SBAS CCA functional sensor. However, the end-use equipment manufacturer remains responsible for meeting the overall environmental qualification at the end-use equipment level.(c) Loss of navigation and loss of integrity indications are limited to temperature testing and the information in RTCA/DO-229E, sections 2.4.1.1.2 and 2.4.1.1.3 is appropriate. The purpose is to ensure that the interface used to indicate the loss of navigation is functional under environmental conditions after the SBAS CCA functional sensor is installed in the end-use equipment. Sections 2.4.1.1.2 and 2.4.1.1.3 indicate that any source that generates the indication can be used since it is the interface and not the detection mechanism that is verified. The temperature testing done at the end-use equipment level is the worst-case scenario. It is not necessary to repeat the CCA level test at room temperature in the end-use equipment since the environmentalqualification adequately addresses testing for these requirements.(d) RTCA/DO-160E section 16 relates to aircraft power supply (refer to TSO paragraph 3.g for environmental qualification requirements). Sections 16.5.1.2 and 16.6.1.2 are for supply voltage modulation (ac) /ripple (dc). Given the potential susceptibility of the SBAS CCA functional sensor to power supply noise, it is prudent to repeat tests at the end-use equipment level on this basis.(e) Sections 4.1 and 4.2 identify the testing end-use equipment manufacturers are required to repeat to demonstrate the SBAS CCA functional sensor continues to meet the Acquisition Time and Reacquisition Time performance requirements relative to Normal/Abnormal Operating Conditions after installation in the end-use equipment. All tests will be run under conditions where the end-use equipment functions are fully enabled to create the worst-case environment.4.1 2.5.4 Initial Acquisition Test Procedures.The information in RTCA/DO-229E, section 2.4.1.1.4 on the initial acquisition test in section 2.5.4 applies. The end-use equipment manufacturer shall repeat the initial acquisition testing described in RTCA/DO-229E, section 2.5.4.4.2 2.5.6 Satellite Reacquisition Time Test.The end-use equipment manufacturer is required to repeat the。
空中导航题目:浅谈卫星导航与惯性导航姓名:罗文学号:150441418专业:交通运输卫星导航与惯性导航摘要:无线电导航与惯性导航是现代民航客机使用的最广泛的导航方式,卫星导航作为无线电导航的重要组成部分,现在以及将来都有着举足轻重的地位。
卫星导航主要由空间部分,控制部分和用户部分组成,卫星相比于路基导航设施有着明显的优势,仅需24颗卫星就可实现对全球提供精确度较高的导航,在加上差分系统的修正,可实现精度导航。
惯性导航系统利用惯性原件以及计算机可以实现完全自主导航,可在洋区,极地等导航设施覆盖不到或精确度较低的地方实现导航,惯性导航是目前唯一被认可的唯一导航方式。
关键字:无线电导航,惯性导航,差分系统,完全自主,唯一导航方式。
第一章卫星导航卫星导航是指利用导航卫星对地面、海洋、空中以及空间用户进行导航定位的技术。
卫星导航最早提于19世纪后半期,但直到20世纪60年代才开始实现。
常见的导航系统有GPS、GLONESS、Compass、Galileo等系统。
卫星导航系统由空间部分、控制部分和用户部分组成。
空间部分由导航卫星构成;控制部分包括世界各地的监测站,地面天线和上行链接和主控站;用户部分通常由接收机等组成。
现代民航运输飞行导航方式正逐渐由传统的VOR、DME、NDB等路基导航设施向星基导航设施过渡,基于性能的导航(PBN)作为未来全球导航技术的主要发展方向,其运行的导航设施主要是全球卫星导航系统(GNSS)。
卫星导航系统可在全球范围为民航客机提供连续精确的位置,时间,速度等信息。
由于卫星导航的实时性,使得飞机摆脱根据导航台飞行的飞行方式,而可以实现点与点之间的直线飞行,从而降低了油耗,节省飞行时间。
卫星导航系统同时也能将飞机飞行实时数据传送给空中交通管理部分,实现对飞行全程的自动监视,卫星导航想对于路基导航有着无可比拟的优越性。
尽管卫星导航导航精度能精确到十米左右,但这样的精度对于飞行起飞的着陆阶段还是不够。
SBAS 即Space Based Augmentation System (DGNSS/DGPS/WAAS/EGNOS)是利用地球静止轨道卫星建立的地区性广域差分增强系统。
目前全球发展的SBAS系统有:欧空局接收卫星导航系统(EGNOS),覆盖欧洲大陆美国的DGPS(Differential GPS),美国雷声公司的广域增强系统(WAAS),覆盖美洲大陆日本的多功能卫星增强系统(MSAS),覆盖亚洲大陆。
三者具有完全兼容的互操作性。
其特点是:1、通过地球静止卫星(GEO)发布包括GPS卫星星历误差改正、卫星钟差改正和电离层改的信息;2、通过GEO卫星发播GPS和GEO卫星完整的数据;3、GEO卫星的导航载荷发射GPS L1测距信号。
差分GPS差分GPS是伴随GPS产生而产生的用于局部区域改进导航精度的一种技术。
一个在已知测量位置的GPS接收机,将其GPS测量导出的解与其测量位置比较,得到改正项,将改正项发送至用户,使用户改进他自己的位置解。
一般说来,存在两种差分GPS概念:1.一接收机置于已知位置,测量由GPS导出的位置解误差(△x,△y,△z),这一信息然后发射到携带主接收机的载体,加到用户估计的坐标中。
用这种技术,位置改正数仅当两个接收机使用同一组卫星时才是有效的。
2.一接收机置于已知位置,确定到所有可见卫星的伪距的误差,并发射至用户。
用户在确定其民航解之前从其测量的伪距中减去此项误差改正。
用这种技术,用户和地面接收机不一定使用一组卫星。
还有一种伪卫星概念。
地面站起着伪卫星的作用,计算所有卫星的伪距偏差,将其与导航数据电文一起发射给用户。
用户采集这些信息,作为正常导航电文的一部分,来改正他的位置解。
DGPS可以将用户的三维定位精度改进至5米水平。
DGPS所以能够提高用户定位精度是基于用户与参考点所蒙受的误差相关这一假设。
事实上,用户星历误差、电离层和对流层延迟影响不能被差分改正完全抵销。
随着用户至参考站距离的增加,误差相关退化,以致用户定位精度降低。
DGPS的部分误差是由于下述事实引起的,即星历误差在用户-卫星视线上的投影不再与参考站-卫星的视线上的投影相同。
另外,如果两个接收机相距很远,穿过电离层的视线也很不同,导致所观测的电离层延迟不同。
对流层延迟的情况类似,但影响较小。
超过100公里,距离误差改正就不足以精确至实现DGPS的全部潜力。
因而DGPS 仅限于局部应用。
覆盖像我国这样大的国家需要几百个参考站才能实现单站差分GPS。
差分技术需要在地面参考点和用户之间的数据链,常用的通信链路有视线(例如VHF,L波段,微波);地波(例如LF,MF,无线电信标);FM副载波。
由于其视线和传播问题,数据链也成为DGPS的作用范围的限制因素。
DGPS的典型例子是美国海岸警卫队(USCG)在沿美国海岸和内河建立DGPS系统,该系统主要用于港口靠泊和进港引导,水文测量,监测和控制港口交通等,包括一个由61个点组成的广播点网和两个控制站。
每一广播实际上是一个局部差分系统(LADGPS),包括两个参考站、两个完好性监测站和无线电信标机组成,整个系统由参考站、广播发射机、控制站、监测站和船上设备组成。
参考站为其覆盖区域的用户产生伪距改正,它装备有高质量的GPS接收机,具有产生RTCM广播电文和同远方控制系统通信的能力。
它进行GPS卫星的完好性检查,也接收完好性监测站来的警戒信号,还准备在失去监测时或者受完好性监测站命令广播完好性警告。
广播发射机包括一个海上无线电信标,实时DGPS改正数据被输入到RTCMSC—104格式,广播至所有的用户。
由两个计算机控制的控制站,一个位于东海岸,一个位于西海岸,每一个用数据通信网连接到在其区域所有的监测站和所有的参考/广播站。
控制站进行系统监测、数据通信网和各地设备的控制。
在紧急情况下,每一站能够处理整个网的事务。
完好性监测站包括一个MSK接收机,一个DGPS接收机和计算机。
计算机检核GPS广播,DGPS改正数据和MSK广播信号。
每一个参考/广播点将有一个完好性监测站。
完好性监测站用实时数据链连到GPS参考接收机,将连续地把在其覆盖地区看到的广播状态通知参考接收机。
船上装备必须有MSK/无线电信标接收机,一个DGPS接收机和电子图显示器。
整个DGPS计划包括DGPS参考站、发射机、监测站和控制站的设计、制作、安装、运作和维持。
系统组建计划投资1700万美元,运作和维持每年500万美元。
USCG的DGPS系统覆盖海岸和主要河流,在内陆留下一些空隙,特别是西部。
美国工程兵部队也计划用USCG的标准和频率建立一些无线电台。
另外,为了使这一系统用于铁路交通控制,联邦铁路局(FRA)计划将LADGPS扩展到48州的全国覆盖,需要增加20到25个站。
加拿大海岸警卫队也正在其沿岸和港口地区与大湖区执行DGPS计划,计划到1998年提供25个站信标DGPS服务。
三、广域差分GPS与局部差分不同,广域差分概念基于由多参考站导出的改正数确定DPGS位置。
现在有一类广域差分系统,概念类似于局部差分,主要不同点是增设多个参考站,利用多参考站得到差分改正,用这些数据连同用户的GPS接收机的原始距离数据计算用户位置。
所有计算在用户位置完成,包括电离层和对流层影响模型化。
Accqpoint/Cue、DCI、Fugro Starfix、JECA Omnistar和Racal SkyFix等公司建立的地区或全球WADGPS系统为这类系统的代表,其中Omnistar的虚拟基站概念似乎别具特色。
它的输出好像一个随用户系统移动的基站,为得到精确的差分改正不必测量基站的位置,在差分改正数中顾及了每个基站每个卫星的对流层和电离层误差,减小了GPS误差空间去相关的影响和参考站的噪声和残余多路径影响。
在计算加到参考站的改正数的权时使用了至卫星的高度角和方位角,从每站的外插改正数加权平均得到最后最佳改正数,权为到参考站的距离和用户端或参考站到卫星的高度角的函数。
最佳化的改正数供给任何能够接收标准RTCM格式的GPS接收机。
商业性的广域系统的差分改正以RTCM—104格式播发,最常用的广播媒介为地球同步卫星和FM副载波。
接收天线为高增益、方向天线或低增益、全方向天线,在用高增益的碟式天线时(大多为沿海、海洋应用),改正数从静态天线通过无线电遥测设备向本地用户广播。
接收机通常为传呼接收机或专门研制的接收机(如 OMNISTAR 6300/7000接收机)。
私人公司的广域系统未见有系统故障报警能力,着重于改进定位精度(一般卫星轨道误差改正有限),主要用于沿岸或陆地实时定位。
在另一类比较规范的WADGPS中,主要误差源被向量化,即分解为卫星星历误差,卫星钟误差和电离层误差,它们被分别加以模型化。
向大范围用户提供误差改正,不再是像DGPS那样为每一卫星的标量距离改正,而是包括卫星星历误差改正、含SA影响的卫星钟误差改正以及电离层时间延迟改正的向量。
差分改正的精度在所监测的区域内大致是一致的,在其边缘地带精度可能略有降低。
广域差分的优点是可以较少数目的参考站向广大地区的用户提供几米的导航和定位精度。
这类WADGPS由一个地面监测网和一个通信链组成。
监测网包括一个(或两个)主站和若干参考站。
每一参考站配备一个高质量的时钟,一台可以跟踪视野内所有卫星的双频GPS接收机。
在每一参考站所得到的GPS测量被发送到主站。
主站根据从参考站采集的信息作出GPS系统完好性判断,并结合已知的参考站位置计算误差改正向量,包括卫星星历误差,卫星钟误差(包含SA影响),以及电离层延迟误差。
完好性告警信息和计算的误差改正经过任何方便的通信链发射给用户。
WADGPS的数据流程可以归结为:1)在已知位置的参考站采集视野内所有卫星的GPS伪距和载波相位。
2)在参考站所得到的所有测量被送到主站。
3)主站计算误差改正向量和判断系统完好性。
4)误差改正向量和完好性信息被发射到用户。
5)用户接收完好性告警信息,用误差改正数改进导航精度。
四、广域增强系统通常的广域差分GPS系统,改进了GPS系统的精度和完好性,并未改进其可用性。
增强型的广域系统,则可以改善GPS的所有三个缺陷。
增强型的广域系统,通常称为广域增强系统(WAAS)。
在WAAS中,携带有导航转发器的地球静止卫星为数据链的一部分,它除了广播完好性信息和矢量改正数以外,还广播类似GPS信号的测距信号,测距信号能够被稍微修改的GPS接收机所接收。
类似GPS信号改善了卫星导航的可用性。
导航转发器工作在GPS的L1频率(1575.42MHz),并被调制以完好性数据,差分改正数,以及伪随机码测距信号。
发射测距码的作用是使地球静止卫星被当作一个GPS卫星用,测距职能使GPS用户可测量至同步卫星的伪距,因而改善了GPS导航的几何,提高了导航的精度。
并以此增强GPS的通用性和服务的连续性。
INMARSAT—3卫星是第一个携带WAAS导航转发器的卫星。
它们按下式信号的功率,θ为载波相位,fL1=1575.42×106Hz为载波频率,与GPS L1一样。
WAAS信号用数据D(t)调制,D(t)携带完好性警告和矢量改正数。
另外,每一信号还调制扩频码X(t)。
像GPS C/A码一样,这个码是码元率为1.023MHz 的±1伪随机码序列。
扩频调制对于WAAS的作用与其对于GPS的作用相同。
它能够在即使有噪声、反射信号和干扰信号时进行精密测距。
它也许可WAAS同GPS信号共享GPS L1频率。
WAAS信号不会干扰现有GPS接收机或不是设计为接收WAAS信号的其他GPS接收机接收GPS信号。
接收机用分离GPS信号同样的扩频机制,能够将WAAS信号与GPS信号区分开来。
事实上,WAAS码是从GPS C/A码同一码族中选出来的。
在1025个可能性的这一码族中GPS仅用36个码,所以为WAAS剩余很多码。
另外,WAAS(C)接收的功率将比GPS信号的规定接收功率稍微弱些。
WAAS的码和载波与GPS同步,所以WAAS提供附加的距离测量。
这一距离测量将改进航空的卫星导航的连续性和时间可用性。
WAAS信号将不会引起GPS接收机的设计有大的变化。
信号工作在GPS L1频率,用同样的扩频码,用二进制相移键控携带数据。
所以,对接收机的最重要变化是对于施加在WAAS电文所载的数据。
为了为所有飞行阶段的导航服务提供对基本 GPS SPS所必要的增强,美国联邦航空局(FAA)正在发展WAAS系统。
该系统覆盖美国、加拿大、波多黎各和太平洋、大西洋沿岸。
项目的目标是支持在直到Ⅰ类精密进近的所有飞行阶段用作主要导航手段的航空要求。
项目从1992年开始执行,分四期完成,1997年将实现初步运行能力,2001年实现最终运行能力。