A new SAE standard for GPS receivers is a natural complement to a newly receptive posture toward innovation unmistakably expressed at high levels in FAA and Mitre (ICNS 2018).  Techniques introduced over decades by this author (many on this site) can finally become operational.

1980s euphoria over GPS success was understandable but decision-makers, lulled into complacency, defined requirements in adherence to antiquated concepts. Familiar examples (full-fix-every-time, with emphasis on position irrespective of dynamics) only begin a broad range revealing opportunities long deferred. “Keep it simple” produced decades of oversimplification, strangling efforts to overcome adversity. “Integration” became a misnomer, inappropriately bestowed as “legacy systems” slavishly followed paths precluding resilience. 

Not all of the issues presented to the National Advisory Board for Satellite Navigation in 2015) are obvious, even to experienced designers. A crucial point is insight, without which even a mathematically 100% correct formulation plus
coding can fail operationally; real-world examples illustrating that point are included in the course described below.

As procedures thus far unalterable are finally considered open to revision,  APPLIED TECHNOLOGY INSTITUTE LLC of Annapolis MD offers a May 21-24 course taught by the author of  capabilities reaching over an exceptionally wide range (inertial, magnetometer, radar, optical, GPS pseudorange, carrier phase, … ).

Comments by former Inst-of-Navigation presidents (no stone unturnedteeming with insights that are hard to find or unavailable elsewhere … ) are likewise true of the course material which, in common with the book (provided as part of the course registration), has a major focus on robustness so urgently needed in coming developments for navigation plus myriad modes of tracking as well). Hope to see you there.

At April’s ICNS meeting (Integrated Communications Navigation and Surveillance) as coauthor with Bill Woodward (Chairman, SAE International Aerospace Avionics Systems Division), I’ll present “NEW INTERFACE REQUIREMENTS: IMPLICATIONS for FUTURE“.  By “future” we indicate the initiation of a task to conclude with a SAE standard that will necessitate appearance of separate satellite measurements to be included among GPS receiver outputs.   Content of the presentation includes flight-validated dramatic improvements in multiple facets applicable to air traffic control (e.g., reduction in area of uncertainty at closest approach point by factors on the order of a million ;  major enhancement of achievable integrity, availability, etc.) — accessible from public domain with no requirements for scientific breakthroughs or new inventions. All benefits are derived from exploiting capabilities that have been available for decades, by discarding outdated practices devised largely to accommodate limitations in yesteryear’s provisions.

Although my writings for years expressed advocacy for these dormant advantages, concrete action was limited to embedded (often proprietary, inflexible) systems plus a modest number of scattered ventures, rather than widespread acceptance offering high accuracy at low cost. Dominance of simplified methods with huge performance penalty continues to this day, despite urgent need to cope with challenges to satellite navigation. For release from this “grip-of-inertia” a standard will mandate presence of individual satellite measurements at receiver output interfaces. The most obvious effect, ability to make use (finally !) of partial data, is only the beginning of a benefit list; advances in main pillars of performance criteria (accuracy, availability, integrity, and continuity) can be intense enough to reconsider some definitions.

Enhancements will materialize not only in aircraft — in air or on ground — but in maritime operation and land vehicles as well, whether manned or unmanned. Future extensions could involve other sensors. The purpose is empowerment of users through removal of constraints currently inhibiting robustness/resilience.  Immediately it is acknowledged — none of this will matter without victory in another area: security.  The battle of the spectrum and subsequent authentication must be won first.  As I noted in an earlier forum, everything I’ve advocated all this time is not a replacement for  but a recommended addition to  that important work.  As satnav cannot exist without authentic data, it cannot be resilient without raw data.

1-page summary


To access the free offer below, become a subscriber by clicking here now. The free video viewing will be available to all subscribers beginning on the afternoon of November 15th 

I’m giving free access to a 20-minute video, available for three days to all subscribers. It is the first of three segments I’ve put together for two reasons:
1) Dearth of time during a short course doesn’t allow adequate coverage of applicable matrix theory in class.
2) The material was organized to drive home a fundamental point: Math without insight is grossly inadequate. That lesson will be useful to professors, instructors, and mentors as well as designers.
I start with a no-math real-world example dramatically illustrating preference for insight over blind acceptance of computer outputs.
Each of the three parts has a preview that can be watched free at any time. Click Here
If you click on any section, options include a preview for no cost (white circle on the right). Attendees of any course I teach will receive free 3-day access all three parts, and others (e.g., students or trainees) would also benefit from this information. An admission: The recording was done during hay-fever season; I sound (and look) like it. That’s unimportant in comparison to the message.
HomePageNewBookPicIn addition you will receive a 100 page excerpt form my latest book GNSS Aided Navigation and Tracking
My website now has excerpts from a wide variety of topics, all of which can be expanded further into helpful learning aids — backed by a long history of real-world experience and insights very much in need today. Occasionally I make incremental additions generated for release. As always, subscribers have the option for subsequent opt-out with no danger of further contact, spam, etc.


A video completed recently provides just enough matrix theory needed for Kalman filtering. It’s available for  (1) purchase or 72-hour rent at low cost or (2) free to those attending courses I teach in 2014 or after (because the short durations don’t allow time to cover it). The one-hour presentation is divided into three sections. Each section has a preview, freely viewable.



The first section, with almost NO math, begins by explaining why matrices are needed — and then immediately emphasizes that MATH ALONE IS NOT ENOUGH, To drive home that point, a dramatic illustration was chosen. Complex motions of a satellite, though represented in a MATHEMATICALLY correct way, were not fully understood by its designers nor by the first team of analysts contracted to characterize it. From those motions, shown with amplitudes enlarged (e.g., doubled or possibly more) for easy visualization, it becomes clear why insight is every bit as important as the math.


EmailMarketingPicFor some viewers the importance of insight alone will be of sufficient interest with no need for the latter two sections. Others, particularly novices aspiring to be designers, will find the math presentation extremely helpful. Straight to the point for each step where matrices are applied, it is just the type of information I was earnestly seeking years ago, whole “pulling teeth” to extract clarification of ONLY NECESSARY theory without OVER simplification.


The presentation supplies matrix theory prerequisites that will assist aspiring designers in formulating linear(ized) estimation algorithms in block (weighted least squares) or sequential (recursive Kalman/EKF) form. Familiar matrix types (e.g., orthogonal, symmetric), their properties, how they are used — and why they are useful — with interpretation of physical examples, enable important operations both powerful and versatile. An enormous variety of applications involving systems of any order can be solved in terms of familiar expressions we saw as teenagers in college.


Useful for either introduction or review, there is no better way to summarize this material than to repeat one word that matters beyond all else — INSIGHT.

John Bortz

In February of this year the navigation community lost a major contributor to navigation — John Bortz. To many his name is best known in connection with “the Bortz equation” which easily deserves a note here to highlight its significance in development of strapdown inertial nav. Before his work in the early 1970s, strapdown was widely considered as something with possible promise “maybe, if only it could ever come out of the lab-&-theory realm” and into operation. Technological capabilities we take for granted today were far less advanced then; among the many state-of-the-art limitations of that time, processing speed is a glaringly obvious example. To make a long story short, John Bortz made it all happen anyway. Applying the previously mentioned equation (outgrowth of an early investigation of Draper Lab’s Dr. J.H. Laning) was only part of his achievement. Working with 1960s hardware and those old computers, he made a historic mark in the annals of strapdown.  Still, importance of that accomplishment should not obscure his other credentials. For example, he also made significant contributions to radio navigation — and he spent the lst two decades of his life as a deacon.

Press Release


James L Farrell launches his new Kindle book – GPS Made Simple


James L Farrell, author of  GNSS Aided Navigation & Tracking & Integrated Aircraft Navigation has just launched his new book on the Amazon platform Kindle. The book is now available for Android tablets, iPads and of course Kindle Fire. The book sells for  $3.99 and available in the  Kindle Store.



Book Description

Publication Date: April 8, 2013
This presentation provides a basic understanding of GPS for those trying to learn it for the first time. Although satellite navigation now includes constellations from Europe and Asia, all have enough in common to focus on GPS for introductory discussion. Material was selected and organized with a a learner’s perspective in mind. for a “straight-to-the-point” exposition with little or no mathematics and, rather than an extensive bibliography, a few few URLs that can be followed towards a wealth of further sources for those interested.

Product Details

  • File Size: 592 KB
  • Publisher: VIGIL, Inc. (April 8, 2013)
  • Sold by: Amazon Digital Services, Inc.
  • Language: English
  • ASIN: B00CA4N4Y8
  • Text-to-Speech: Enabled
  • X-Ray: Not Enabled
  • Lending: Enabled

I perform functional formulations and algorithm generation plus validation for both simulation and operational purposes in system integration. Specific areas include navigation, communication, data integrity, and tracking for aerospace, applying modern estimation to data from various sources (COMM, gyros, accelerometers, GPS/GNSS, radar, optical, etc.). 

Complete Viewable & printable Resume Click Here
(opens in new window)


At ION GNSS 2011 in Portland OR, Javad Ashjaee, James L. Farrell and others participated in a panel discussing the U.S. Dept. of Homeland Security’s concerns on the effects of GPS jamming and spoofing on our national critical infrastructure.


 As Dr. Todd Humphreys noted, U.S. Dept. of Homeland Security recently completed a risk assessment of the effects of GPS jamming and spoofing on national critical infrastructure. Some of us participated as subject matter experts in this assessment.


The DHS report, which is the most thorough one to date on this topic, has left many people saying “Yes, it’s a problem. Now what?”

This panel addressed the question “Now what?”


Topic: How do we secure civil GNSS?



    • 8:30: Welcome and introduction: Moderator introduces topic, format, and ground rules
    • 8:40: Moderator introduces panelists
    • 8:45: Moderator frames the central question: “How do we secure civil GNSS?”
    • 8:50: Logan Scott
    • 9:00: Panel/audience response to Logan’s remarks
    • 9:10: Javad Ashjaee
    • 9:20: Panel/audience response to Javad’s remarks
    • 9:30: Mark Psiaki
    • 9:40: Panel/audience response to Mark’s remarks
    • 9:50: Questions from audience, discussion among panelists

10:05 — 10:35: Morning break

  • 10:35: Moderator welcomes audience and panel back, summarizes morning discussion
  • 10:40: Oscar Pozzobon
  • 10:50: Panel/audience response to Oscar’s remarks
  • 11:00:James Farrell
  • 11:10: Panel/audience response to James’s remarks
  • 11:20: Felix Kneißl
  • 11:30: Panel/audience response to Felix’s remarks
  • 11:40: Questions from audience; discussion among panelists
  • 12:10: Moderator and panelists offer concluding remarks
  • 12:15: Panel concludes


September 19-23, 2011 (Tutorials: September 19-20)
Oregon Convention Center, Portland, Oregon





A subsequent experiment conducted in Texas, attracting national attention at that time, became the topic of eMail communications among several professionals in the satnav community.  That sequence of communications resulted in a summary published in GPSWorld.