Todd Walter

Todd Walter is a senior research engineer at Stanford University. He has been active in the development of the Wide Area Augmentation System and related systems around the globe. His focus is on the provision of certified integrity for aviation applications.

	Article Innovation: Digging into GPS Integrity November 1, 2011 By: Grace Xingxin Gao,Liang Heng,Per Enge,Todd Walter There are four important requirements of any navigation system: accuracy, availability, continuity, and integrity. In this month’s column we take a look at one particular aspect of GPS integrity: that of the signal in space and find out how trustworthy is the satellite ephemeris and clock...more >>
	Article Integrity for Non-Aviation Users July 1, 2011 By: Per Enge,Sam Pullen,Todd Walter Non-aviation users of satellite- and ground-based augmentation systems do not require the conservative level of integrity built into these systems for aviation users. Removing it can produce substantial benefits in terms of smaller error bounds and improved availability.
	Article Future Augmented March 1, 2010 By: Juan Blanch,Per Enge,Todd Walter After reviewing current performance of WAAS, EGNOS, and MSAS, the authors present expected future performance, including the benefits of GPS L5. They evaluate the impact of the Indian GAGAN and Russian SDCM systems on global coverage and examine southward expansions for the original three SBASs....more >>
	Article Shaping Aviation Integrity April 1, 2008 By: Boris Pervan,Juan Blanch,Livio Gratton,Per Enge,Todd Walter Relative RAIM and absolute RAIM both enable an aircraft to raise a flag within seconds of receiving faulty data. This article evaluates the protection-level equations for both methods, and examines them in the light of GNSS constellations optimized for 24, 27, and 30 satellites.