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Good, better, best: expanding the wide area augmentation system / T. Schrempp in GPS world, vol 19 n° 1 (January 2008)

Public [article]  inGPS world > vol 19 n° 1 (January 2008) . - pp 62 - 67 Titre : Good, better, best: expanding the wide area augmentation system Type de document : Article/Communication Auteurs : T. Schrempp, Auteur Année de publication : 2008 Article en page(s) : pp 62 - 67 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] navigation aérienne [Termes IGN] transport aérien [Termes IGN] Wide Area Augmentation System Résumé : (Editeur) Air travel promises to become safer and cheaper thanks to the Wide Area Augmentation System (WAAS). It assists or augments GPS by providing the increased accuracy, availability, continuity, and integrity necessary for aircraft navigation. Unaugmented, or standalone, GPS isn't accurate enough for some types of runway approach procedures. Using geostationary Earth orbit (GEO) communications satellites, WAAS provides corrections to the GPS satellite orbit and clock information in a satellite's navigation message as well ; as ionospheric delay information. These corrections permit a user's receiver to compute a more accurate position, often to better than 1 meter horizontally and 2 meters vertically, with a 95% confidence. WAAS also increases the availability and continuity of GPS for aircraft navigation by requiring fewer redundant observations for determining a valid position. Availability is also increased through the provision of the additional GEO ranging signals. But perhaps most importantly, WAAS provides the increased integrity needed for a safety-of-life navigation system. Within 6 seconds of a fault detection, an alarm message corrects the error or allows a safe transition to an alternative navigation procedure. The advantages of WAAS for aviation include greater runway capability, reduced separation standards which allow increased capacity in a given airspace without increased risk, more direct enroute flight paths, new precision approach services, reduced and simplified equipment onboard aircraft, and significant government cost savings due to the elimination of maintenance costs associated with older, more expensive ground-based navigation aids. But WAAS not only benefits GPS users in the sky. Many GPS users on terra firma are making use of the increased accuracy and availability afforded by WAAS. For example, according to the FAA, OnStar has added WAAS capability to the GPS receivers in General Motors 2008 product year vehicles. And even surveyors are making use of the WAAS ranging signals for improving real-time kinematic survey operation. While WAAS was already a much-valued addition to standalone GPS, significant improvements were made to WAAS over the past three years, including expansion of the reference station network and the commissioning of two new GEOs. 2008 will see even more enhancements. In this month's column, we take a look at WAAS's recent upgrades and take a peek into its future. Copyright Questex Media Group Inc Numéro de notice : A2008-161 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29156 [article]

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