Bio


I am the director of the wide-area differential Global Navigation Satellite System(GNSS) laboratory at Stanford University. My work focuses on implementing high-integrity air navigation systems. I am also active in the international standards bodies coordinating the use of GNSS to implement these systems.

Academic Appointments


  • Professor (Research), Aeronautics and Astronautics
  • Sr Research Engineer, Aeronautics and Astronautics

Honors & Awards


  • Leadership Award in Signal Design, GPS World Magazine (September, 2015)
  • Distinguished Service Award, Institute of Navigation (January, 2012)
  • Kepler Award, Institute of Navigation (September, 2010)
  • Thurlow Award, Institute of Navigation (January, 2008)
  • Fellow of the ION, Institute of Navigation (June, 2006)
  • Early Achievement Award, Institute of Navigation (June, 2000)

Boards, Advisory Committees, Professional Organizations


  • Member, National Space-Based Positioning, Navigation, and Timing Advisory Board (2019 - Present)
  • Member, IEEE (2014 - Present)
  • President, Institute of Navigation (2010 - 2012)
  • Member, Institute of Navigation (1994 - Present)

Professional Education


  • Ph.D., Stanford University, Applied Physics (1994)
  • M.S., Stanford University, Applied Physics (1990)
  • B.S., Rensselaer Polytechnic Institute, Physics (1987)

Current Research and Scholarly Interests


High integrity satellite navigation for guiding aircraft, including satellite based augmentation systems (SBAS) and advanced receiver autonomous integrity monitoring (ARAIM).

Stanford Advisees


All Publications


  • Determination of Fault Probabilities for ARAIM IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Walter, T., Blanch, J., Gunning, K., Joerger, M., Pervan, B. 2019; 55 (6): 3505–16
  • Quantum-resistant authentication algorithms for satellite-based augmentation systems NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Neish, A., Walter, T., Enge, P. 2019; 66 (1): 199–209

    View details for DOI 10.1002/navi.287

    View details for Web of Science ID 000462203300016

  • Broadband LEO Constellations for Navigation NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Reid, T. R., Neish, A. M., Walter, T., Enge, P. K. 2018; 65 (2): 205–20

    View details for DOI 10.1002/navi.234

    View details for Web of Science ID 000439832100005

  • Worldwide Vertical Guidance of Aircraft Based on Modernized GPS and New Integrity Augmentations PROCEEDINGS OF THE IEEE Walter, T., Enge, P., Blanch, J., Pervan, B. 2008; 96 (12): 1918-1935
  • Robust Detection of Ionospheric Irregularities NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Walter, T., et al 2001; 48 (2): 89–100
  • Wide area augmentation of the global positioning system PROCEEDINGS OF THE IEEE Enge, P., Walter, T., Pullen, S., Kee, C., Chao, Y. C., Tsai, Y. J. 1996; 84 (8): 1063-1088
  • An Assessment of GPS Spoofing Detection Via Radio Power and Signal Quality Monitoring for Aviation Safety Operations IEEE INTELLIGENT TRANSPORTATION SYSTEMS MAGAZINE Miralles, D., Levigne, N., Bornot, A., Rouquette, P., Akos, D. M., Chen, Y., La, S., Walter, T. 2020; 12 (3): 136–46
  • Receiver States for SBAS Data Authentication Neish, A., Walter, T., Fernandez-Hernandez, I., Inst Navigat INST NAVIGATION. 2020: 1059–69
  • Independent Time Synchronization for Resilient GNSS Receivers Fernandez-Hernandez, I., Walter, T., Neish, A., O'Driscoll, C., Inst Navigat INST NAVIGATION. 2020: 964–78
  • Stress Testing Advanced RAIM Airborne Algorithms Blanch, J., Walter, T., Inst Navigat INST NAVIGATION. 2020: 421–39
  • Evaluating the Application of PPP Techniques to ARAIM Using Flight Data Phelts, R., Gunning, K., Blanch, J., Walter, T., Inst Navigat INST NAVIGATION. 2020: 379–85
  • Design and analysis of a public key infrastructure for SBAS data authentication NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Neish, A., Walter, T., Powell, J. D. 2019; 66 (4): 831–44

    View details for DOI 10.1002/navi.338

    View details for Web of Science ID 000507100800010

  • Gaussian Bounds of Sample Distributions for Integrity Analysis IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Blanch, J., Walter, T., Enge, P. 2019; 55 (4): 1806–15
  • Signal Deformation Monitoring for Anomalous Multipath Threats Phelts, R., Walter, T., Inst Navigat INST NAVIGATION. 2019: 1023–30
  • Development of Advanced RAIM Minimum Operational Performance Standards Blanch, J., Walter, T., Berz, G., Burns, J., Clark, B., Joerger, M., Mabilleau, M., Martini, I., Milner, C., Pervan, B., Lee, Y., Inst Navigat INST NAVIGATION. 2019: 1381–91
  • SBAS Data Authentication: A Concept of Operations Neish, A., Walter, T., Powell, J., Inst Navigat INST NAVIGATION. 2019: 1812–23
  • Integrity for Tightly Coupled PPP and IMU Gunning, K., Blanch, J., Walter, T., de Groot, L., Norman, L., Inst Navigat INST NAVIGATION. 2019: 3066–78
  • Going Back for the Future: Large/Mega LEO Constellations for Navigation Reid, T., Gunning, K., Perkins, A., Lo, S., Walter, T., Inst Navigat INST NAVIGATION. 2019: 2452–68
  • Increasing International Civil Aviation Resilience: A Proposal for Nomenclature, Categorization and Treatment of New Interference Threats Fernandez-Hernandez, I., Walter, T., Alexander, K., Clark, B., Chatre, E., Hegarty, C., Appel, M., Meurer, M., Inst Navigat INST NAVIGATION. 2019: 389–407
  • SBAS Corrections for PPP Integrity with Solution Separation Gunning, K., Blanch, J., Walter, T., Inst Navigat INST NAVIGATION. 2019: 707–19
  • Development and Evaluation of Airborne Multipath Error Bounds for L1-L5 Blanch, J., Walter, T., Phelts, R., Inst Navigat INST NAVIGATION. 2019: 53–61
  • Reducing Computational Load in Solution Separation for Kalman Filters and an Application to PPP Integrity Blanch, J., Gunning, K., Walter, T., De Groot, L., Norman, L., Inst Navigat INST NAVIGATION. 2019: 720–29
  • Safety Analysis of Ranging Biases on the WAAS GEOs Walter, T., Blanch, J., Altshuler, E., Inst Navigat INST NAVIGATION. 2019: 113–30
  • Paper Trends in ION Conferences from 2007-2018 Perkins, A., Walter, T., Inst Navigat INST NAVIGATION. 2019: 340–48
  • Design and Analysis of a Public Key Infrastructure for SBAS Data Authentication Neish, A., Walter, T., Powell, J., Inst Navigat INST NAVIGATION. 2019: 964–88
  • Lower Bounds in Optimal Integrity Monitoring Blanch, J., Walter, T., Inst Navigat INST NAVIGATION. 2019: 915–24
  • SIS Monitoring for ARAIM in the Absence of Precise Clock Estimates Gunning, K., Walter, T., Powell, D., Inst Navigat INST NAVIGATION. 2019: 785–801
  • Standards for ARAIM ISM Data Analysis Walter, T., Blanch, J., Gunning, K., Inst Navigat INST NAVIGATION. 2019: 777–84
  • WAAS at 15 NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Walter, T., Shallberg, K., Altshuler, E., Wanner, W., Harris, C., Stimmler, R. 2018; 65 (4): 581–600

    View details for DOI 10.1002/navi.252

    View details for Web of Science ID 000454313700007

  • Validation of the Unfaulted Error Bounds for ARAIM NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Walter, T., Gunning, K., Phelts, R., Blanch, J. 2018; 65 (1): 117–33
  • Effective GPS Spoofing Detection Utilizing Metrics from Commercial Receivers Manfredini, E., Akos, D. M., Chen, Y., Lo, S., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2018: 672–89
  • Spoofing Detection for Airborne GNSS Equipment Hegarty, C., Odeh, A., Shallberg, K., Wesson, K., Walter, T., Alexander, K., Inst Navigat INST NAVIGATION. 2018: 1350–68
  • Design and evaluation of integrity algorithms for PPP in kinematic applications Gunning, K., Blanch, J., Walter, T., de Groot, L., Norman, L., Inst Navigat INST NAVIGATION. 2018: 1910–39
  • A Proposed Concept of Operations for Advanced Receiver Autonomous Integrity Monitoring Blanch, J., Walter, T., Enge, P., Burns, J., Mabilleau, M., Martini, I., Boyero, J., Berz, G., Inst Navigat INST NAVIGATION. 2018: 1084–90
  • Parameter Selection for the TESLA Keychain Neish, A., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2018: 2155–71
  • Effect of Aircraft Banking on ARAIM Performance Phelts, R., Blanch, J., Gunning, K., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2018: 2632–41
  • GNSS Multipath Error Modeling for Automotive Applications Khanafseh, S., Kujur, B., Joerger, M., Walter, T., Pullen, S., Blanch, J., Doherty, K., Norman, L., de Groot, L., Pervan, B., Inst Navigat INST NAVIGATION. 2018: 1573–89
  • Ionospheric Rates of Change Walter, T., Blanch, J., de Groot, L., Norman, L., Joerger, M., Inst Navigat INST NAVIGATION. 2018: 4158–70
  • Fixed Subset Selection to Reduce Advanced RAIM Complexity Blanch, J., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2018: 88–98
  • A Formula for Solution Separation without Subset Solutions for Advanced RAIM Blanch, J., Walter, T., Enge, P., IEEE IEEE. 2018: 316–26
  • GNSS Multipath Detection in Urban Environment Using 3D Building Model Zhang, S., Lo, S., Chen, Y., Walter, T., Enge, P., IEEE IEEE. 2018: 1053–58
  • WASS at 15 Walter, T., Shallberg, K., Altshuler, E., Wanner, W., Harris, C., Stimmler, R., Inst Navigat INST NAVIGATION. 2018: 301–21
  • Quantum Resistant Authentication Algorithms for Satellite-Based Augmentation Systems Neish, A., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2018: 365–79
  • Protection Levels after Fault Exclusion for Advanced RAIM NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Blanch, J., Walter, T., Enge, P. 2017; 64 (4): 505–13

    View details for DOI 10.1002/navi.210

    View details for Web of Science ID 000418762800007

  • Improved User Position Monitor for WAAS NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Walter, T., Blanch, J. 2017; 64 (1): 165–75

    View details for DOI 10.1002/navi.180

    View details for Web of Science ID 000403758600012

  • Theoretical Results on the Optimal Detection Statistics for Autonomous Integrity Monitoring NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Blanch, J., Walter, T., Enge, P. 2017; 64 (1): 123–37

    View details for DOI 10.1002/navi.175

    View details for Web of Science ID 000403758600009

  • Multi-GNSS Constellation Anomaly Detection and Performance Monitoring Gunning, K., Walter, T., Enge, P., INST NAVIGAT INST NAVIGATION. 2017: 1051–62
  • Characterization of GLONASS Broadcast Clock and Ephemeris: Nominal Performance and Fault Trends for ARAIM Gunning, K., Walter, T., Enge, P., INST NAVIGAT INST NAVIGATION. 2017: 170–83
  • Catalog and Description of GPS and WAAS L1 C/A Signal Deformation Events Shallberg, K. W., Ericson, S. D., Phelts, E., Walter, T., Kovach, K., Altshuler, E., INST NAVIGAT INST NAVIGATION. 2017: 508–20
  • Validation of the Unfaulted Error Bounds for ARAIM Walter, T., Gunning, K., Phelts, R., Blanch, J., Inst Navigat INST NAVIGATION. 2017: 1–19
  • The Benefit of Low Cost Accelerometers for GNSS Anti-Spoofing Lo, S., Chen, Y., Reid, T., Perkins, A., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2017: 775–96
  • WAAS Signal Deformation Monitor Performance: Beyond the ICAO Threat Model Phelts, R., Shallberg, K., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2017: 713–24
  • A MATLAB Toolset to Determine Strict Gaussian Bounding Distributions of a Sample Distribution Blanch, J., Walter, T., Enge, P., INST NAVIGAT INST NAVIGATION. 2017: 4236–47
  • Feasibility of fault exclusion related to advanced RAIM for GNSS spoofing detection Kuusniemi, H., Blanch, J., Chen, Y., Lo, S., Innac, A., Ferrara, G., Honkala, S., Bhuiyan, M. H., Thombre, S., Soderholm, S., Walter, T., Phelts, R., Enge, P., INST NAVIGAT INST NAVIGATION. 2017: 2359–70
  • Orbital representations for the next generation of satellite-based augmentation systems GPS SOLUTIONS Reid, T. G., Walter, T., Enge, P. K., Sakai, T. 2016; 20 (4): 737-750
  • Preliminary availability assessment to support single-frequency SBAS development in the Korean region GPS SOLUTIONS Bang, E., Lee, J., Walter, T., Lee, J. 2016; 20 (3): 299-312
  • GNSS Integrity in The Arctic NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Reid, T., Walter, T., Blanch, J., Enge, P. 2016; 63 (4): 469-492
  • Improved Ephemeris Monitoring for GNSS Walter, T., Gunning, K., Blanch, J., Inst Navigat INST NAVIGATION. 2016: 600–608
  • Determination of Fault Probabilities for ARAIM Walter, T., Blanch, J., Joerger, M., Pervan, B., IEEE IEEE. 2016: 451–61
  • Improved User Position Monitor for WAAS Walter, T., Blanch, J., Inst Navigat INST NAVIGATION. 2016: 343–52
  • Mitigation of short duration satellite outages for Advanced RAIM and other integrity systems based on GNSS Blanch, J., Chen, Y., Phelts, R., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2016: 1688–95
  • A Simple Satellite Exclusion Algorithm for Advanced RAIM Blanch, J., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2016: 239–44
  • Leveraging Commercial Broadband LEO Constellations for Navigation Reid, T. R., Neish, A. M., Walter, T. F., Enge, P. K., Inst Navigat INST NAVIGATION. 2016: 2300–2314
  • Demonstrating ARAIM on UAS using Software Defined Radio and Civilian Signal GPS L1/L2C and GLONASS G1/G2 Chen, Y., Perkins, A., Lo, S., Akos, D. M., Blanch, J., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2016: 231–38
  • Satellite Selection for Multi-Constellation SBAS Walter, T., Blanch, J., Kropp, V., Inst Navigat INST NAVIGATION. 2016: 1350–59
  • A Simple Position Estimator That Improves Advanced RAIM Performance IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Blanch, J., Walter, T., Enge, P., Kropp, V. 2015; 51 (3): 2485-U960
  • GNSS Multipath and Jamming Mitigation Using High-Mask-Angle Antennas and Multiple Constellations IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS Heng, L., Walter, T., Enge, P., Gao, G. X. 2015; 16 (2): 741-750
  • Aviation Benefits from Satellite Navigation NEW SPACE Enge, P., Enge, N., Walter, T., Eldredge, L. 2015; 3 (1): 19–35
  • Baseline Advanced RAIM User Algorithm and Possible Improvements IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Blanch, J., Walker, T., Enge, P., Lee, Y., Pervan, B., Rippl, M., Spletter, A., Kropp, V. 2015; 51 (1): 713-732
  • GNSS Integrity in The Arctic Reid, T. R., Walter, T., Blanch, J., Enge, P. K., Inst Navigat INST NAVIGATION. 2015: 1726–40
  • Progress on Working Group-C Activities on Advanced RAIM Blanch, J., Walter, T., Enge, P., Burns, J., Alexander, K., Boyero, J., Lee, Y., Pervan, B., Joerger, M., Khanafseh, S., Rippl, M., Martini, I., Perea, S., Kropp, V., Macabiau, C., Suard, N., Berz, G., Inst Navigat INST NAVIGATION. 2015: 629–38
  • Validating Nominal Bias Error Limits Using 4 years of WAAS Signal Quality Monitoring Data Phelts, R., Altshuler, E., Walter, T., Inst Navigat INST NAVIGATION. 2015: 956–63
  • GPS Multi-Frequency Carrier Phase Characterization During Strong Equatorial Ionospheric Scintillation Xu, D., Morton, Y., Akos, D., Walter, T., Inst Navigat INST NAVIGATION. 2015: 3787–96
  • A Comparative Study of Triple Frequency GPS Scintillation Signal Amplitude Fading Characteristics at Low Latitudes Jiao, Y., Morton, Y., Akos, D., Walter, T., Inst Navigat INST NAVIGATION. 2015: 3819–25
  • Fast Multiple Fault Exclusion with a Large Number of Measurements Blanch, J., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2015: 696–701
  • Characterization of GPS Clock and Ephemeris Errors to Support ARAIM Walter, T., Blanch, J., Inst Navigat INST NAVIGATION. 2015: 920–31
  • Airborne Mitigation Of Constellation Wide Faults Walter, T., Blanch, J., Inst Navigat INST NAVIGATION. 2015: 676–86
  • Future Dual-Frequency GPS Navigation System for Intelligent Air Transportation Under Strong Ionospheric Scintillation IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS Seo, J., Walter, T. 2014; 15 (5): 2224-2236
  • Effects of solar cycle 24 activity onWAAS navigation SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Datta-Barua, S., Walter, T., Bust, G. S., Wanner, W. 2014; 12 (1): 46-63
  • Architectures for Advanced RAIM: Offline and Online Blanch, J., Walter, T., Enge, P., Pervan, B., Joerger, M., Khanafseh, S., Burns, J., Alexander, K., Boyero, J., Lee, Y., Kropp, V., Milner, C., Macabiau, C., Suard, N., Berz, G., Rippl, M., Inst Navigat INST NAVIGATION. 2014: 787–804
  • Crowdsourcing Arctic Navigation Using Multispectral Ice Classification & GNSS PROCEEDINGS OF THE 27TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS 2014) Reid, T., Walter, T., Enge, P., Fowler, A. 2014: 707-721
  • Scintillation Characterization for WAAS in the Auroral Region Altshuler, E., Shallberg, K., Potter, B. J., Walter, T., Inst Navigat INST NAVIGATION. 2014: 1126–37
  • Single Antenna GPS Spoof Detection that is Simple, Static, Instantaneous and Backwards Compatible for Aerial Applications McMilin, E., De Lorenzo, D. S., Walter, T., Lee, T. H., Enge, P., Inst Navigat INST NAVIGATION. 2014: 2233–42
  • Mitigation of Nominal Signal Deformations on Dual-Frequency WAAS Position Errors Wong, G., Chen, Y., Phelts, R., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2014: 3129–47
  • VPL Parameter Determination for Improved Performance of Advanced RAIM Lee, J., Kim, D., Lee, J., Walter, T., Inst Navigat INST NAVIGATION. 2014: 3566–74
  • Experimentally Recorded Amplitude and Phase Scintillation through a Spirent Simulator Jayawardena, T., Ali, A. M., Forte, B., Kinrade, J., Mitchell, C., Smith, S., Walter, T., Inst Navigat INST NAVIGATION. 2014: 1108–14
  • Evaluation of a covariance-based clock and ephemeris error bounding algorithm for SBAS Blanch, J., Walter, T., Enge, P., Stern, A., Altshuler, E., Inst Navigat INST NAVIGATION. 2014: 3270–76
  • Exclusion for Advanced RAIM: Requirements and a Baseline Algorithm International Technical Meeting of the Institute-of-Navigation Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2014: 99–107
  • Reduced Subset Analysis for Multi-Constellation ARAIM International Technical Meeting of the Institute-of-Navigation Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2014: 89–98
  • Development of a Real-time GNSS Software Receiver for Evaluating RAIM in Multi-constellation International Technical Meeting of the Institute-of-Navigation Chen, Y., Lo, S., Akos, D. M., Choi, M., Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2014: 525–533
  • The Effect of Nominal Signal Deformations on ARAIM Users International Technical Meeting of the Institute-of-Navigation Phelts, R. E., Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2014: 56–67
  • DME/TACAN interference mitigation for GNSS: algorithms and flight test results GPS SOLUTIONS Gao, G. X., Heng, L., Hornbostel, A., Denks, H., Meurer, M., Walter, T., Enge, P. 2013; 17 (4): 561-573
  • Critical Elements for a Multi-Constellation Advanced RAIM NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Blanch, J., Walter, T., Enge, P., Wallner, S., Fernandez, F. A., Dellago, R., Ioannides, R., Hernandez, I. F. 2013; 60 (1): 53-69

    View details for DOI 10.1002/navi.29

    View details for Web of Science ID 000339565800005

  • Incorporating GLONASS into Aviation RAIM Receivers International Technical Meeting of the Institute-of-Navigation Walter, T., Blanch, J., Choi, M. J., Reid, T., Enge, P. INST NAVIGATION. 2013: 239–249
  • Advanced RAIM System Architecture with a Long Latency Integrity Support Message Blanch, J., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2013: 2605–13
  • Constructing Ionospheric Irregularity Threat Model for Korean SBAS Bang, E., Lee, J., Lee, J., Seo, J., Walter, T., ION INST NAVIGATION. 2013: 296–306
  • Evolution of SBAS: Two Frequencies & Multiple Constellations Walter, T., Inst Navigat INST NAVIGATION. 2013: 2394–2439
  • Qualifying an L5 SBAS MOPS Ephemeris Message to Support Multiple Orbit Classes Reid, T., Walter, T., Enge, P., Inst Navigat INST NAVIGATION. 2013: 825–43
  • Dual Frequency SBAS Trial and Preliminary Results for East-Asia Region Sakai, T., Hoshinoo, K., Walter, T., Inst Navigat INST NAVIGATION. 2013: 912–20
  • The Influence of the Ionosphere on SBAS Walter, T., Inst Navigat INST NAVIGATION. 2013: 2373–93
  • Overcoming RFI with High Mask Angle Antennas and Multiple GNSS Constellations Heng, L., Walter, T., Enge, P., Gao, G., Inst Navigat INST NAVIGATION. 2013: 3433–42
  • Implementation of the L5 SBAS MOPS Walter, T., Blanch, J., Enge, P., Inst Navigat INST NAVIGATION. 2013: 814–24
  • Optimal Positioning for Advanced Raim NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Blanch, J., Walter, T., Enge, P. 2013; 60 (4): 279-289

    View details for DOI 10.1002/navi.49

    View details for Web of Science ID 000339567500003

  • Near Term Improvements to WAAS Availability International Technical Meeting of the Institute-of-Navigation Blanch, J., Walter, T., Phelts, R. E., Enge, P. INST NAVIGATION. 2013: 71–77
  • L1/L5 SBAS MOPS Ephemeris Message to Support Multiple Orbit Classes International Technical Meeting of the Institute-of-Navigation Reid, T., Walter, T., Enge, P. INST NAVIGATION. 2013: 78–92
  • Signal Deformation Monitoring for Dual-Frequency WAAS International Technical Meeting of the Institute-of-Navigation Phelts, R. E., Wong, G., Walter, T., Enge, P. INST NAVIGATION. 2013: 93–106
  • Results on the Optimal Detection Statistic for Integrity Monitoring International Technical Meeting of the Institute-of-Navigation Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2013: 262–273
  • GPS Signal-in-Space Integrity Performance Evolution in the Last Decade IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Heng, L., Gao, G. X., Walter, T., Enge, P. 2012; 48 (4): 2932-2946
  • Satellite Navigation for Aviation in 2025 PROCEEDINGS OF THE IEEE Blanch, J., Walter, T., Enge, P. 2012; 100: 1821-1830
  • Evolving WAAS to Serve L1/L5 Users NAVIGATION-JOURNAL OF THE INSTITUTE OF NAVIGATION Walter, T., Blanch, J., Phelts, R. E., Enge, P. 2012; 59 (4): 317-327

    View details for DOI 10.1002/navi.21

    View details for Web of Science ID 000209006500006

  • The impact the lonosphere on GNSS Aufmentation Walter, T., ION INST NAVIGATION. 2012: 1070–78
  • GLONASS Signal-in-Space Anomalies Since 2009 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Heng, L., Gao, G. X., Walter, T., Enge, P. INST NAVIGATION. 2012: 833–842
  • L1/L5 SBAS MOPS to Support Multiple Constellations 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2012: 1287–1297
  • Advanced RAIM User Algorithm Description: Integrity Support Message Processing, Fault Detection, Exclusion, and Protection Level Calculation 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Blanch, J., Walter, T., Enge, P., Lee, Y., Pervan, B., Rippl, M., Spletter, A. INST NAVIGATION. 2012: 2828–2849
  • Measuring Code-Phase Differences due to Inter-Satellite Hardware Differences 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Wong, G., Chen, Y., Phelts, R. E., Walter, T., Enge, P. INST NAVIGATION. 2012: 2150–2158
  • Impact of Personal Privacy Devices for WAAS Aviation Users 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Gao, G. X., Gunning, K., Walter, T., Enge, P. INST NAVIGATION. 2012: 235–241
  • Evaluation of Multi-Constellation Advanced RAIM for Vertical Guidance using GPS and GLONASS Signals with Multiple Faults 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Choi, M., Blanch, J., Walter, T., Akos, D., Enge, P. INST NAVIGATION. 2012: 884–892
  • A Framework for Analyzing Architectures that Support ARAIM 25th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2012: 2850–2857
  • Automated Verification of Potential GPS Signal-In-Space Anomalies Using Ground Observation Data IEEE/ION Position Location and Navigation Symposium (PLANS) Heng, L., Gao, G. X., Walter, T., Enge, P. IEEE. 2012: 1111–1118
  • OPTIMAL POSITIONING FOR ADVANCED RAIM International Technical Meeting (ITM) of the Institute-of-Navigation (ION) Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2012: 1624–1631
  • Statistical Characterization of GLONASS Broadcast Clock Errors and Signal-In-Space Errors International Technical Meeting (ITM) of the Institute-of-Navigation (ION) Heng, L., Gao, G. X., Walter, T., Enge, P. INST NAVIGATION. 2012: 1697–1707
  • Availability Impact on GPS Aviation due to Strong Ionospheric Scintillation IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Seo, J., Walter, T., Enge, P. 2011; 47 (3): 1963-1973
  • Correlation of GPS signal fades due to ionospheric scintillation for aviation applications ADVANCES IN SPACE RESEARCH Seo, J., Walter, T., Enge, P. 2011; 47 (10): 1777-1788
  • Alternative Characterization of Analog Signal Deformation for GNSS-GPS Satellites International Technical Meeting of the Institute of Navigation Wong, G., Phelts, R. E., Walter, T., Enge, P. INST NAVIGATION. 2011: 497–507
  • First Signal in Space Analysis of GLONASS K-1 Thoelert, S., Erker, S., Furthner, J., Meurer, M., Gao, G. X., Heng, L., Walter, T., Enge, P., ION INST NAVIGATION. 2011: 3076–82
  • Optimization of a Vertical Protection Level Equation for Dual Frequency SBAS International Technical Meeting of the Institute of Navigation Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2011: 459–463
  • Statistical Characterization of GPS Signal-In-Space Errors International Technical Meeting of the Institute of Navigation Heng, L., Gao, G. X., Walter, T., Enge, P. INST NAVIGATION. 2011: 312–319
  • Demonstrations of Multi-Constellation Advanced RAIM for Vertical Guidance using GPS and GLONASS Signals 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Choi, M., Blanch, J., Akos, D., Heng, L., Gao, G., Walter, T., Enge, P. INST NAVIGATION. 2011: 3227–3234
  • SBAS and GBAS Integrity for Non-Aviation Users: Moving Away from "Specific Risk" International Technical Meeting of the Institute of Navigation Pullen, S., Walter, T., Enge, P. INST NAVIGATION. 2011: 533–545
  • Statistical Characterization of GLONASS Broadcast Ephemeris Errors 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Heng, L., Gao, G. X., Walter, T., Enge, P. INST NAVIGATION. 2011: 3109–3117
  • Breaking the Ice: Navigation in the Arctic 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Gao, G. X., Heng, L., Walter, T., Enge, P. INST NAVIGATION. 2011: 3767–3772
  • A Proposal for Multi-Constellation Advanced RAIM for Vertical Guidance 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Blanch, J., Walter, T., Enge, P., Wallner, S., Fernandez, F. A., Dellago, R., Ioannides, R., Pervan, B., Hernandez, I. F. INST NAVIGATION. 2011: 2665–2680
  • Evolving WAAS to Serve L1/L5 Users 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Walter, T., Blanch, J., Phelts, R. E., Enge, P. INST NAVIGATION. 2011: 2495–2504
  • Advanced RAIM Demonstration using Four Months of Ground Data International Technical Meeting of the Institute of Navigation Choi, M., Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2011: 279–284
  • A Clock and Ephemeris Algorithm for Dual Frequency SBAS 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2011: 2513–2519
  • Bounding Errors Caused by Nominal GNSS Signal Deformations 24th International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS) Wong, G., Phelts, R. E., Walter, T., Enge, P. INST NAVIGATION. 2011: 2657–2664
  • Reversion from L1-L5 Dual to L5 Single Frequency WAAS in the Presence of RF Interference IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Jan, S., Walter, T., Enge, P. 2010; 46 (3): 1110-1126
  • RAIM with Optimal Integrity and Continuity Allocations Under Multiple Failures IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Blanch, J., Walter, T., Enge, P. 2010; 46 (3): 1235-1247
  • Unaugmented GPS-Based Flight Inspection System IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Kim, E., Walter, T., Powell, J. D. 2010; 46 (2): 717-724
  • Coverage Improvement for Dual Frequency SBAS 2010 International Technical Meeting of the Institute-of-Navigation Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2010: 344–353
  • GPS in Mid-life with an International Team of Doctors Analyzing IIF-1 Satellite Performance and Backward-Compatibility 23rd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-2010) Gao, G. X., Heng, L., Wong, G., Phelts, E., Blanch, J., Walter, T., Enge, P., Erker, S., Thoelert, S., Meurer, M. INST NAVIGATION. 2010: 1597–1604
  • Prototyping Advanced RAIM for Vertical Guidance 23rd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-2010) Blanch, J., Choi, M. J., Walter, T., Enge, P. INST NAVIGATION. 2010: 285–291
  • Vertical Protection Level Equations for Dual Frequency SBAS 23rd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-2010) Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2010: 2031–2041
  • GPS Signal-in-Space Anomalies in the Last Decade Data Mining of 400,000,000 GPS Navigation Messages 23rd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-2010) Heng, L., Gao, G. X., Walter, T., Enge, P. INST NAVIGATION. 2010: 3115–3122
  • Characterization of Signal Deformations for GPS and WAAS Satellites 23rd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-2010) Wong, G., Phelts, R. E., Walter, T., Enge, P. INST NAVIGATION. 2010: 3143–3151
  • GPS Ephemeris Error Screening and Results for 2006-2009 2010 International Technical Meeting of the Institute-of-Navigation Heng, L., Gao, G. X., Walter, T., Enge, P. INST NAVIGATION. 2010: 1014–1022
  • MATLAB Algorithm Availability Simulation Tool GPS SOLUTIONS Jan, S., Chan, W., Walter, T. 2009; 13 (4): 327-332
  • Compass-M1 Broadcast Codes in E2, E5b, and E6 Frequency Bands IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING Gao, G. X., Chen, A., Lo, S., De Lorenzo, D., Walter, T., Enge, P. 2009; 3 (4): 599-612
  • Characteristics of deep GPS signal fading due to ionospheric scintillation for aviation receiver design RADIO SCIENCE Seo, J., Walter, T., Chiou, T., Enge, P. 2009; 44
  • Evaluation of Signal in Space Error Bounds to Support Aviation Integrity 22nd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-09) Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2009: 1317–1329
  • Characterizing Nominal Analog Signal Deformation on GNSS Signals 22nd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-09) Phelts, R. E., Walter, T., Enge, P. INST NAVIGATION. 2009: 1343–1350
  • Availability Benefit of Future Dual Frequency GPS Avionics under Strong Ionospheric Scintillation 22nd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-09) Seo, J., Walter, T., Enge, P. INST NAVIGATION. 2009: 1216–1224
  • Hysteresis in RAIM 22nd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-09) Blanch, J., Mayer, C., Lo, S., Walter, T., Enge, P. INST NAVIGATION. 2009: 2818–2823
  • Methodology and Case Studies of Signal-in-Space Error Calculation Top-down Meets Bottom-up 22nd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-09) Gao, G. X., Tang, H., Blanch, J., Lee, J., Walter, T., Enge, P. INST NAVIGATION. 2009: 2824–2831
  • Bounding higher-order ionosphere errors for the dual-frequency GPS user RADIO SCIENCE Datta-Barua, S., Walter, T., Blanch, J., Enge, P. 2008; 43 (5)
  • Altitudinal variation of midlatitude localized TEC enhancement from ground- and space-based measurements SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Datta-Barua, S., Mannucci, A. J., Walter, T., Enge, P. 2008; 6 (10)
  • Position Error Bound Calculation for GNSS using Measurement Residuals IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Blanch, J., Walter, T., Enge, P. 2008; 44 (3): 977-984
  • Wide area augmentation system-based might inspection system JOURNAL OF AIRCRAFT Kim, E., Walter, T., Powell, J. D. 2008; 45 (2): 614-621

    View details for DOI 10.2514/1.32531

    View details for Web of Science ID 000254761600029

  • Improving GPS-based landing system performance using an empirical barometric altimeter confidence bound IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS Jan, S., Gebre-Egziabher, D., Walter, T., Enge, P. 2008; 44 (1): 127-146
  • Future Architectures to Provide Aviation Integrity 2008 National Technical Meeting of the Institute-of-Navigation Walter, T., Blanch, J., Enge, P., Pervan, B., Gratton, L. INST NAVIGATION. 2008: 394–401
  • Compass-M1 Broadcast Codes and Their Application to Acquisition and Tracking 2008 National Technical Meeting of the Institute-of-Navigation Gao, G. X., Chen, A., Lo, S., De Lorenzo, D., Walter, T., Enge, P. INST NAVIGATION. 2008: 133–141
  • Understanding the GIOVE-B Broadcast Codes of the Galileo System 42nd Asilomar Conference on Signals, Systems and Computers Gao, G. X., Akos, D., Walter, T., Enge, P. IEEE. 2008: 2086–2090
  • Understanding PHMI for Safety of Life Applications in GNSS 2007 National Technical Meeting of the Institute-of-Navigation Blanch, J., Walter, T., Enge, P. INST NAVIGATION. 2007: 305–310
  • Adaptive Carrier Smoothing Using Code and Carrier Divergence 2007 National Technical Meeting of the Institute-of-Navigation Kim, E., Walter, T., Powell, J. D. INST NAVIGATION. 2007: 141–152
  • Model Analysis on the Performance for an Inertial Aided FLL-Assisted-PLL Carrier-Tracking Loop in the Presence of Ionospheric Scintillation 2007 National Technical Meeting of the Institute-of-Navigation Chiou, T., Gebre-Egziabher, D., Walter, T., Enge, P. INST NAVIGATION. 2007: 1276–1295
  • Galileo GIOVE-A Broadcast E5 Codes and their Application to Acquisition and Tracking 2007 National Technical Meeting of the Institute-of-Navigation Gao, G. X., De Lorenzo, D. S., Chen, A., Lo, S. C., Akos, D. M., Walter, T., Enge, P. INST NAVIGATION. 2007: 936–946
  • A Reference Point-based Precise Relative Positioning Method Using a Single Frequency Receiver 2006 National Technical Meeting of the Institute-of-Navigation Kim, E., Walter, T., Powell, J. D. INST NAVIGATION. 2006: 283–292
  • Optimizing WAAS Accuracy/Stability For a Single Frequency Receiver Kim, E., Walter, T., Powell, J., NAVSTAR INST NAVIGATION. 2006: 962–70
  • Bounding Higher Order Ionosphere Errors for the Dual Frequency GPS User 19th International Technical Meeting of the Satellite Division of the Institute-of-Navigation Datta-Barua, S., Walter, T., Blanch, J., Enge, P. INST NAVIGATION. 2006: 1377–1392
  • Code Generation Scheme and Property Analysis of Broadcast Galileo L1 and E6 Signals 19th International Technical Meeting of the Satellite Division of the Institute-of-Navigation Gao, G. X., Spilker, J., Walter, T., Enge, P., Pratt, A. R. INST NAVIGATION. 2006: 1526–1534
  • WAAS-based threat monitoring for a Local Airport Monitor (LAM) that supports Category I Precision Approach IEEE/ION Position, Location, and Navigation Symposium Rife, J., Pullen, S., Walter, T., Phelts, E., Pervan, B., Enge, P. IEEE. 2006: 468–482
  • Galileo-GPS RAIM for Vertical Guidance 2006 National Technical Meeting of the Institute-of-Navigation Ene, A., Blanch, J., Walter, T. INST NAVIGATION. 2006: 432–440
  • A development of WAAS-aided Flight Inspection Truth System 2006 IEEE/ION POSITION, LOCATION AND NAVIGATION SYMPOSIUM, VOLS 1-3 Kim, E., Peled, U., Walter, T., Powell, J. D. 2006: 61-70
  • Field Data Analysis for a Range-Based Local Airport Monitor for WAAS 2006 National Technical Meeting of the Institute-of-Navigation Seo, J., Rife, J., Pullen, S., Walter, T., Enge, P. INST NAVIGATION. 2006: 748–758
  • Comparison of master station and user algorithms for wide-area augmentation system JOURNAL OF GUIDANCE CONTROL AND DYNAMICS Kee, C., Walter, T., Chao, Y. C., Tsai, Y. J., Enge, P., Parkinson, B. W. 1997; 20 (1): 170-176
  • High integrity multipath mitigation techniques for ground reference stations 10th International Technical Meeting of the Satellite Division of the Institute-of-Navigation Dai, D. H., Walter, T., Comp, C. J., Tsai, Y. J., Ko, P. Y., Enge, P., Powell, J. D. INST NAVIGATION. 1997: 593–604
  • Ionospheric estimation and integrity threat detection ION National Meeting on Navigation and Positioning in the Information Age Hansen, A. J., Chao, Y. C., Walter, T., Enge, P. INST NAVIGATION. 1997: 883–889
  • Improving WAAS integrity and availability: UDRE and GIVE time updates 10th International Technical Meeting of the Satellite Division of the Institute-of-Navigation COMP, C., Gazit, R., Walter, T., Enge, P. INST NAVIGATION. 1997: 1315–1324
  • Ionospheric correction using tomography 10th International Technical Meeting of the Satellite Division of the Institute-of-Navigation Hansen, A. J., Walter, T., Enge, P. INST NAVIGATION. 1997: 249–257
  • A proposed integrity equation for WAAS MOPS 10th International Technical Meeting of the Satellite Division of the Institute-of-Navigation Walter, T., Enge, P., Hansen, A. INST NAVIGATION. 1997: 475–484
  • Integration of wide area DGPS with local area kinematic DGPS IEEE 1996 Position Location and Navigation Symposium (PLANS 96) LAWRENCE, D., Evans, J., Chao, Y. C., Tsai, Y. J., Cohen, C., Walter, T., Enge, P., Powell, J. D., Parkinson, B. I E E E. 1996: 523–529
  • Quality control algorithms on Wide-area Reference Station for WAAS 52nd Annual Meeting of the Institute-of-Navigation on Navigational Technology for the 3rd Millenium Kee, C., Walter, T., Enge, P., Parkinson, B. INST NAVIGATION. 1996: 487–495
  • Generation of ionospheric correction and confidence estimates for WAAS 52nd Annual Meeting of the Institute-of-Navigation on Navigational Technology for the 3rd Millenium Chao, Y. C., Tsai, Y. J., Evans, J., Kee, C., Walter, T., ENGE, P. K., Powell, J. D., Parkinson, B. W. INST NAVIGATION. 1996: 139–146
  • An algorithm for inter-frequency bias calibration and application to WAAS ionosphere modeling 8th International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GPS-95) Chao, Y. C., Tsai, Y. J., Walter, T., Kee, C. D., Enge, P., Parkinson, B. INST NAVIGATION. 1995: 639–646
  • Observed GPS signal continuity interruptions 8th International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GPS-95) COBB, H. S., LAWRENCE, D., Christie, J., Walter, T., Chao, Y. C., Powell, J. D., Parkinson, B. INST NAVIGATION. 1995: 793–795
  • A low temperature gyroscope clock for gravitational redshift experiments XXXth Rencontres de Moriond on Dark Matter in Cosmology, Clocks and Tests of Fundamental Laws Buchman, S., Turneaure, J. P., Walter, T., Everitt, C. W. EDITIONS FRONTIERES. 1995: 429–436
  • Validation or the RTCA message format for WAAS 8th International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GPS-95) Tsai, Y. J., Enge, P., Chao, Y. C., Walter, T., Kee, C. D., Evans, J. INST NAVIGATION. 1995: 661–670
  • CHARACTERIZING FREQUENCY STABILITY - A CONTINUOUS POWER-LAW MODEL WITH DISCRETE SAMPLING IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT WALTER, T. 1994; 43 (1): 69–79

    View details for DOI 10.1109/19.286357

    View details for Web of Science ID A1994NQ12800013

  • FLIGHT TRIALS OF THE WIDE AREA AUGMENTATION SYSTEM (WAAS) 7th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation (ION GPS-94) Walter, T., Kee, C., Chao, Y. C., Tsai, Y. J., PELED, U., Ceva, J., Barrows, A., Abbot, E., Powell, J. D., Enge, P., Parkinson, B. INST NAVIGATION. 1994: 1537–1546
  • AUTONOMOUS INTEGRITY MONITORING AND WIDE AREA DGPS 1994 National Technical Meeting on Navigating the Earth and Beyond Walter, T., Pervan, B., Enge, P., HERENDEEN, J., Levin, P. L. INST NAVIGATION. 1994: 155–163
  • DISCRETE SIMULATION OF POWER-LAW NOISE KASDIN, N. J., WALTER, T., IEEE I E E E. 1992: 274–83
  • AN ULTRA HIGH-VACUUM LOW-TEMPERATURE GYROSCOPE CLOCK 19TH INTERNATIONAL CONF ON LOW TEMPERATURE PHYSICS ( LT-19 ) Walter, T., Turneaure, J. P., Buchman, S., Everitt, C. W., Keiser, G. M. ELSEVIER SCIENCE BV. 1990: 155–156