Segmenting GNSS Outages


GRIPS Presentation - RIN INC2015 - Dr Sally BaskerI presented a paper on GRIPS (GPS jammer Risk Identification, assessment and Planning System) at the Royal Institute of Navigation’s First International Navigation Conference (INC2015) in Manchester (24-26 February 2015). During my presentation I focused on the potential losses arising from GNSS outages and I indicated the importance of segmenting GNSS outages as part of the risk assessment process. I’m writing a few words in response to further questions.


Many of us would agree that there are many different GNSS outage mechanisms, although the outcomes may appear similar. During my GRIPS presentation, I briefly discussed segmenting GNSS outages by source, purpose and owner-experience.


An obvious top-level segmentation is whether the source is man-made or natural:

  • Man-made causes include radio frequency (RF) interference, engineering failure and human errors.
  • Natural causes include physical (e.g. terrain or the built environment) and atmospheric (e.g. the due to the ionosphere) mechanisms.


My next level of segmentation is the purpose of the outage.

I have two main categories of intentional GNSS outages:

  • Malicious (e.g. crime, warfare or terrorism).
  • Misguided (e.g. privacy or cracking).

When the purpose is malicious, the originator of the GNSS outage wants to inflict some form of loss on a third party including: loss of life, injuries and other economic losses.

When the purpose is misguided, the originator of the GNSS outage aims to derive personal gain and is unaware that he or she may be inflicting some form of loss on a third party:

  • The owner of a personal privacy device may want to stop their boss tracking them and isn’t aware that he/she is inflicting loss on an airport.
  • A cracker (described by Raymond in ‘How to become a hacker‘ as people who get a kick out of breaking into computers and phreaking the phone system) may want to build an internet jammer design and try it out for fun, but doesn’t consider the downstream impact.

I have three main categories of unintentional GNSS outages:

  • Man-made Mistakes (e.g. human error or technical failure).
  • Natural events (e.g. no purpose due to the surface or atmospheric environment).

Man-made mistakes happen:

  • Human error may be due to the failure of a process or procedure where a jammer is inadvertently turned on and left to jam an area.
  • Technical failure may be due to GNSS system faults (e.g. a data upload or a failed satellite) or to faulty user equipment (e.g. a failed antenna cable or a dead battery). It may also be due to other systems or user equipment that interferes with GNSS.

The natural environment also causes GNSS outages:

  • On the surface, the natural terrain and built environment can cause occultation.
  • The atmosphere also has an effect primarily due to the impact of solar activity on the ionosphere, but I also wonder whether ash clouds from large volcanic eruptions could cause GNSS outages (given that they have caused climate changes).


The GNSS outage risk owner’s status also contributes when segmenting GNSS outages.

For intentional outages (Malicious or Misguided), the owner may be the target of the outage or suffering from collateral damage (collateral damage is incidental to the intended target).

For unintentional outages, the owner’s culture may contribute in terms of:

  • Process / procedure design.
  • System engineering and maintenance.
  • Procurement of inadequate operational systems (e.g. for operating in urban canyon or in regions where there is known ionospheric scintillation).

Scheme for Segmenting GNSS Outages

My scheme for segmenting GNSS outages is presented below. Clicking on the image opens a pdf version in a new window.

Scheme for Segmenting GNSS Outages - Dr Sally Basker

This illustrates my current segmentation and is the basis for my risk assessment process.

I’d love to hear your comments. Please consider liking/sharing this page with your friends and colleagues.


We have always been a fan of the interesting, methodical and technically astute ways Dr. Sally Basker (PhD, BEng, FRIN) has of looking at and explaining things.

In one of her recent efforts she outlined 21 different types of GNSS disruptions. Not only is this an interesting mental model for policy makers and technologies alike, but it should be yet another clarion call for governments and industries to Protect, Toughen and Augment GNSS services.

Dr. Basker’s matrix of 21 types of disruption represents thousands of possible sources, methods and motives, any one of which could result in a disastrous incident with lives lost and significant economic damage.

Thank you Dr. Basker for helping us get our heads around a very large, very complex set of threats and vulnerabilities. Your insight has given the rest of us a method of clearer thinking, even if those thoughts can be pretty scary.

Dana A. Goward

President, Resilient Navigation & Timing Foundation

Learn more about Segmenting GNSS Outages and GRIPS

GRIPS is the GPS jammer Risk Identification, assessment and Planning System. It aims to help governments, companies and industries to develop a proportionate and cost-effective response to GPS jammers and other outages.

Segmenting GNSS outages is the basis for GRIPS.

Contact Dr Sally Basker

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