Foreign Airlines to Use GPS for San Francisco Landings

Asiana Airlines Inc. flight 214 failed to reach the runway
at San Francisco International Airport before touching down
 on July 6, 2013, causing the first fatal commercial plane
accident in the U.S. in four years.
Photographer: David Paul Morris/Bloomberg

As reported by Bloomberg News: Non-U.S. carriers landing at San Francisco International Airport, where a plane flown by South Korea’s Asiana Airlines Inc. (020560), plowed into a seawall, must use global-positioning systems when landing, regulators said.

The U.S. Federal Aviation Administration issued the requirement and cited an increase in the number of aborted landing approaches since the July 6 crash of Asiana Flight 214, which killed three people. Jets executing the maneuver included one from Taiwan’s Eva Airways Corp. (2618), the FAA said yesterday.

Flight 214’s crash rekindled concern in the U.S. that foreign pilots rely too heavily on automated systems instead of flying manually. The Boeing Co. 777 neared the San Francisco airport using visual cues and its crew didn't comment on a critical loss of airspeed until it was less than 100 feet (30 meters) off ground, investigators have said.

“The FAA has done a good thing here,” said John Nance, an aviation safety consultant and a former commercial pilot. “They’ve got enough of our tower operators that can tell you when you assign a visual approach to these pilots from foreign carriers, they’re all over the sky.”

The increase in aborted landings, which are known as go-arounds, involved foreign airlines flying visual approaches, the FAA said in an e-mailed statement. Until the glide-slope indicators are available on Runways 28 Left and 28 Right in late August, the agency will assign instrument approaches to foreign carriers, according to the statement.

Eva Airways
One of the go-arounds being reviewed by the FAA involved an Eva Airways flight on July 23 in which a plane approached San Francisco at a lower altitude than is normal, according to the U.S. agency.
Airport construction closed the glide-slope indicator on the day of the Asiana crash, the first fatal airliner accident in the U.S. in four years. Instead, pilots were instructed to use visual approaches, U.S. National Transportation Safety Board Chairman Deborah Hersman said earlier this month.

Three aviators who flew for Asiana or who helped train crews in Korea said in interviews this month that pilots for the Seoul-based airline rarely flew manually, even though they were well-trained on automated systems. The glide-slope indicator helps pilots stay on the right path toward touchdown, and is vital when visibility is limited.

South Korea’s government has begun an investigation to determine whether Flight 214’s crew was appropriately trained. Two South Korean pilot unions, meanwhile, have said the NTSB’s focus on “possibility of pilot error” risks skewing the results of the U.S. inquiry into the accident.

‘Major Disconnect’
Nance, the consultant, said the Asiana case underscored the danger of overdependence on technology.

“In Asiana, you had two senior pilots up there who weren’t really pilots, they were systems operators,” said Nance, who is based in University Place, Washington. “This has nothing to do with intellect. It is a major disconnect between policies that the nations and the International Civil Aviation Organization and basically the world’s airlines have signed onto with increasing automation.”

The next step should include barring all foreign carriers from flying into the U.S. until their pilots are properly trained to fly under visual conditions, Nance said. With technology always vulnerable to failure, pilots need the skills to fly manually so they can handle emergency situations, he said.

“If we’re going to put a pilot up here, we need to have him or her knowledgeable of what it means to be a pilot,” Nance said. “That means when everything else goes to heck in a handbasket, you can fly the airplane.”

The San Francisco Chronicle reported the requirement yesterday.

NASA Van Allen radiation belt probes provide data to help predict space weather for satellites

As reported by Nanowerk News: Using data from NASA satellites, scientists have discovered a massive particle accelerator in the heart of one of the harshest regions of near-Earth space, a region of super-energetic, charged particles surrounding the globe and known as the Van Allen radiation belts.

New results from NASA's Van Allen Probes show the acceleration energy is in the belts themselves. Local bumps of energy kick particles inside the belts to ever-faster speeds, much like a well-timed push on a moving swing. Knowing the location of the acceleration within the radiation belts will help scientists improve predictions of space weather, which can be hazardous to satellites near Earth such as the GPS and GNSS satellites in Low Earth Orbit (LEO). The results were published Thursday in the journal Science.

This video illustrates changes in the shape and intensity of a cross section of the Van Allen belts.

"Until the 1990s, we thought the Van Allen belts were pretty well-behaved and changed slowly," says Geoff Reeves, lead author on the paper and a radiation belt scientist at Los Alamos National Laboratory in Los Alamos, N.M. "With more and more measurements, however, we realized how quickly and unpredictably the radiation belts change. They are basically never in equilibrium, but in a constant state of change."
In order for scientists to understand such changes better, the twin Van Allen Probes fly straight through this intense area of space. One of the top priorities for the mission, launched in August, is to understand how particles in the belts are accelerated to ultra-high energies.

By taking simultaneous measurements with advanced technology instruments, the Van Allen Probes were able to distinguish between two broad possibilities on what accelerates the particles to such amazing speeds. The possibilities are radial acceleration or local acceleration. In radial acceleration, particles are transported perpendicular to the magnetic fields that surround Earth, from areas of low magnetic strength far from Earth to areas of high magnetic strength closer to Earth. Physics dictates particle speeds in this scenario will increase as the magnetic field strength increases. The speed of the particles would increase as they move toward Earth, much the way a rock rolling down a hill gathers speed due to gravity.

Simulated Van Allen Belts generated by a plasma thruster
 in tank #5 Electric Propulsion Laboratory at the
 then-called Lewis Research Center, Cleveland, Ohio.

The local acceleration theory proposes the particles gain energy from a local energy source, similar to the way warm ocean water can fuel a hurricane above it.

Reeves and his team found they could distinguish between these two theories when they observed a rapid energy increase in the radiation belts Oct. 9. The observations did not show an intensification in particle energy starting at high altitude and moving gradually toward Earth, as would be expected in a radial acceleration scenario. Instead, the data showed an increase in energy that started right in the middle of the radiation belts and gradually spread both inward and outward, implying a local acceleration source. The research shows this local energy comes from electromagnetic waves coursing through the belts, tapping energy from other particles residing in the same region of space.

"These new results go a long way toward answering the questions of where and how particles are accelerated to high energy," said Mona Kessel, Van Allen Probes program scientist in Washington. "One mission goal has been substantially addressed."

The challenge for scientists now is to determine which waves are at work. The Van Allen Probes, which are designed to measure and distinguish between many types of electromagnetic waves, will tackle this task, too.

The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., built and operates the twin Van Allen Probes for NASA's Science Mission Directorate. The Van Allen Probes are the second mission in NASA's Living With a Star program, managed by NASA's Goddard Space Flight Center in Greenbelt, Md. The program explores aspects of the connected sun-Earth system that directly affect life and society.

Court stops scientists from publishing codes that could wirelessly lockpick Porsches

As Reported by the Verge: Three cryptography experts from UK and Dutch universities have cracked the codes used to start luxury cars such as Audis, Bentleys, Porsches, and Lamborghinis, knowledge that could allow anyone with the right tools to wirelessly lock-pick a $300,000 car. The researchers were preparing to publish a paper in August explaining the method used to penetrate Megamos Crypto, the algorithm-based system used to verify an owner's key. However, Volkswagen's parent, which owns the four brands, has secured an injunction against the University of Birmingham's Flavio Garcia from a UK court.

The scientists argued that "the public have a right to see weaknesses in security on which they rely exposed," but a judge ruled three weeks ago that "car crime will be facilitated" if the scientists publish the algorithm. Volkswagen had asked them to publish a redacted version without the codes, but they declined. Since then, the decision has become part of a wider discussion about car security.

It emerged in court that their complex mathematical investigation examined the software behind the code. It has been available on the internet since 2009.

Reviewing scientists said they had probably used a technique called "chip slicing" which involves analyzing a chip under a microscope and taking it to pieces and 'reverse engineering' or inferring the algorithm from the arrangement of the microscopic transistors on the chip itself – a process that costs around £50,000 ($77,000USD). The judgment was handed down three weeks ago without attracting any publicity, but has now become part of a wider discussion about car manufacturers' responsibilities relating to car security.

The scientists said they examined security on everything from Oyster cards to cars to enable manufacturers to identify weaknesses and improve on them.

The injunction is a temporary step in the case brought by Volkswagen, so it's possible the decision could be reversed. In the meantime, we'll be on the lookout for PhDs driving 911s.

GPS spoofing demonstrated on super-yacht in the Mediterranean

As reported by FoxNews: The world’s GPS system is vulnerable to hackers or terrorists who could use it to hijack ships -- even commercial airliners, according to a frightening new study that exposes a huge potential hole in national security.

Using a laptop, a small antenna and an electronic GPS “spoofer” built for $3,000, GPS expert Todd Humphreys and his team at the University of Texas took control of the sophisticated navigation system aboard an $80 million, 210-foot super-yacht in the Mediterranean Sea. “We injected our spoofing signals into its GPS antennas and we’re basically able to control its navigation system with our spoofing signals,” Humphreys told Fox News.

By feeding counterfeit radio signals to the yacht, the UT team was able to drive the ship far off course, steer it left and right, potentially take it into treacherous waters, even put it on a collision course with another ship. All the time, the ship’s GPS system reported the vessel was calmly moving in a straight line, along its intended course. No alarms, no indication that anything was amiss.

Capt. Andrew Schofield, who invited Humphreys and his team aboard to conduct the experiment told Fox News he and his crew were stunned by the results.

“Professor Humphreys and his team did a number of attacks and basically we on the bridge were absolutely unaware of any difference,” Schofield said. “I was gobsmacked -- but my entire deck team was similarly gobsmacked,” he told Fox News.

White Rose of Drachs

The possible consequences, according to Humphreys, are both ominous and far-reaching.

“For maritime traffic, there are big implications,” Humphreys told Fox News from the bridge of the White Rose of Drachs. “You’ve got 90 percent of the world’s cargo going across the seas. Imagine shutting down a port. Imagine running a ship aground. These are the kinds of implications we’re worried about.”

As the Costa Concordia tragically proved, a cruise ship off-course can have disastrous results. The Exxon Valdez was only narrowly off its intended track when it ran aground on Bligh Reef, spilling 11 million gallons of oil into Prince William Sound.

Humphreys told Fox News the easiest and most sinister “spoof” is to slowly slide a vessel onto a parallel course. Over time, the compass might read the same heading, but the ship could be far from where the crew thinks it is.

“You’re actually moving about a kilometer off of your intended track in a parallel line and you could be running aground instead of going through the proper channel,” Humphreys said.

And because aircraft have a similar navigation system to that aboard the White Rose of Drachs, Humphreys says a commercial airliner could be “spoofed” as well.

“Going after an expensive vessel on the seas and going after a commercial airliner has a lot of parallels,” he told Fox News.

The government is aware of this critical vulnerability. Last year, Fox News reported exclusively on a more primitive experiment Humphreys conducted using a small, unmanned drone. He was able to feed “spoofing” signals into the drone’s GPS, causing it to nearly fall out of the sky. As a result, Humphreys was called before Congress to testify, and also spoke with officials from the FAA, CIA and Pentagon.

This latest experiment takes Humphreys’ research to a whole new level.

“Before we couldn’t control the UAV. We could only push it off course. This time my students have designed a closed loop controller such that they can dictate the heading of this vessel even when the vessel wants to go a different direction,” Humphreys said.

Yet the Department of Homeland Security has -- according to Humphreys -- been “fumbling around in the dark” on GPS security, doing little to address the threat. Texas Congressman Mike McCaul, chairman of the Homeland Security Committee is incensed.

“It's a very serious homeland security issue that we've asked the secretary to review and look at and she's never responded to my requests,” McCaul told Fox News. “The department seems to be thumbing its nose at it, saying it has no jurisdiction over this issue and not really showing any interest in this issue at all.”

McCaul, along with Senators Coburn and Collins have asked the Government Accountability Office to look into what DHS is and isn’t doing to address this critical threat to national security.  A draft report is due in August, which could, depending on the results, trigger more Congressional hearings.
Meantime, Schofield is sounding a global alarm.

“People need to know this kind of thing is possible with a relatively small budget and they can with a very simple system steer the ship off-course -- without the Captain knowing,” he told Fox News.

Finding Mobile GPS Jammers using ad-hoc networks

GPS/GNSS jamming systems (sometimes referred to as personal privacy devices) are illegal, and for good reason - they're potentially dangerous.

As reported by InsideGNSS: GPS/GNSS technology constitutes a fundamental element for new intelligent transport systems (ITSs) and their applications, such as advanced driver assistance, dangerous goods tracking, and distance- based toll systems. Due to the weak strength of navigation signals from distant satellites, however, these applications are threatened by malicious as well as unintentional interference.

In particular, so-called in-car jammers — also known as “personal privacy devices” — represent a serious threat for GNSS-based systems and applications.

A common Chinese made GPS Jammer - illegal in the USA
purchasable in the UK, but illegal to use.

These jammers are cheap devices able to obscure, partially or totally, the navigation signals received not only by the operator’s vehicle but also by other receivers in the vicinity.

The introduction of standards for vehicular ad-hoc networks (VANETs) sometimes referred to Car2Car or V2V systems, enables the exchange of data regarding detected interference events. This data exchange can be used to enhance the awareness of interference sources, allowing their localization and mitigation, thus increasing the reliability of future ITSs.

Jamming devices could be thwarted using ad-hoc
vehicle networks - which are being developed in the USA
as well as the EU

GNSS Interference Detection and Localization 
Interest in developing GNSS interference detection and localization capabilities has increased steadily in the last few years. The first efforts in this direction have come for military applications, like the jammer detection and location (JLOC) system developed and propsed by Dr. Alison Brown with NAVSYS. This system provides situational awareness on GPS interference events to U.S. military personnel and predicts effects worldwide to enhance battlefield situational awareness and mission planning.

In the case of identified GPS threats, the system disseminates alerts and reports to subscribed JLOC users through the SIPRNet (Secure Internet Protocol Router Network), a system of interconnected computer networks used by the U.S. departments of defense and state to transmit classified information. The core element is the JLOC master station, operated by the U.S. National Geospatial-Intelligence Agency (NGA), which collects information on interference events through dedicated sensors incorporating GPS receivers. These sensors generate reports when they detect signal degradation as measured by carrier-to-noise ratio (C/N0) readings.

For the actual localization of the interference source, angle-of-arrival (AOA) information is collected from receivers capable of digital beam-forming, while time-difference-of-arrival (TDOA) measurements are computed with snapshots of data from multiple locations.

Further studies have been done to integrate mobile devices, such as cell phones, into the network of sensors. Also airborne sensors that can be carried on small unmanned aerial vehicles (UAVs) are envisaged for possible use in future jammer location systems.

Small UAV (drones) could be used to identify GPS jamming
sources in the USA

Interference monitoring and localization systems have been developed to protect safety critical aviation services as required by the International Civil Aviation Organization (ICAO) for GPS-based approach procedures.

In this application, location of interference sources is commonly based on direction-finding sensors. For example, in the United States the localization of interference is performed by the combined use of airborne (AIMDS), transportable (TIMDS), portable (PIMDS), handheld (HIMDS), and fixed (FIMDS) interference monitoring and detection systems. In Europe, similar systems are operated, such as the so-called GIMOS (GNSS Interference Monitoring System) in Germany.

A GBAS reference station outside of an airport.

The problem that can be caused for aviation by GPS jammers became very visible in November 2009 at the Newark Liberty International Airport (New York City). Without an appropriate interference localization system in place, it took more than three months to find the reason for periodic outages of the airport’s ground-based augmentation system (GBAS) reference stations: a GPS jammer transmitting from a vehicle passing near the airport. The airport eventually tackled the problem by making infrastructural changes, such as relocating the GBAS reference antennas over a wider area and enhancing interference detection and localization capabilities.

For maritime applications, the threat represented by jammers became evident in 2008, when the General Lighthouse Authorities of the United Kingdom and Ireland (GLA) conducted a series of sea-trials with the aim of characterizing the full effects of GPS jamming on safe navigation at sea. The test unveiled serious effects on GLA differential GPS (DGPS) reference stations and GPS receivers on ships, as well as radar systems using GPS as their time reference.

These results gave rise to the GAARDIAN/SENTINEL projects. The GAARDIAN project developed and deployed probe sensors at various locations around the United Kingdom and Ireland to continuously report on the integrity, continuity, accuracy, and reliability of GPS signals. The monitoring network was then further expanded by including the Ordnance Survey’s OS Net, consisting of more than 100 continuously operating GNSS receivers. This system bases detection of anomalies on a mask for C/N0 measurements.

The SENTINEL project later added interference localization capability to this network through the use of handheld GPS interference detection devices. AOA, TDOA, and differential-received-signal-strength (DRSS)–based geolocation are currently under investigation.

A down-to-earth alternative

Another way to cope with jammers is to deploy backup systems that do not depend on satellite signals, but rely on terrestrial signals instead. In America radio-navigation and air-traffic-control systems based on terrestrial beacons, which predate GPS, were supposed to be phased out by 2018 in favor of satellite-based alternatives, under a modernization program called NextGen, overseen by the Federal Aviation Administration (FAA). Switching to satellite-based air-traffic control would, for example, allow more direct routes and save fuel, because aircraft would no longer have to follow a 'wiggly' route from one ground-based beacon to another.

In a paper presented at the NAV10 conference in London in December, Mitch Narins, chief systems engineer at the FAA, and colleagues described the Newark jamming incident as “a valuable lesson” because it highlighted the risks of becoming too dependent on satellite-based systems that were vulnerable to disruption. Mr Narins and his team are now investigating whether the old-style terrestrial systems can be modernized and extended to provide a backup that could take over in the event of GPS failures. They expect to make their recommendations in 2013 or 2014, in time for implementation to begin in 2016.

An eLoran reference station

Elsewhere, eLoran is another non-satellite-based alternative which has many cheerleaders. It is an enhanced version of Loran-C, which is itself an improved version of the original Loran (“long-range navigation”) system developed in the 1940s. Once widely used in America, Japan and parts of Europe, Loran fell out of favor with the emergence of satellite-based systems. But its proponents have continued to develop the technology, and eLoran is now accurate to within 10 meters, which is comparable to GPS. “It is terrestrial as opposed to spaced-based, uses very high-powered signals rather than low-powered ones and it's very low frequency instead of high,” says Sally Basker, president of the International Loran Association. “All of which means its failure mechanisms are different to GPS and other satellite-navigation systems.”

Enthusiasm for eLoran is strongest in Britain, where the government awarded a 15-year contract in 2007 to develop eLoran for use by shipping in western Europe. A ministerial decision to move from the development to the operational phase is expected shortly. In the United States and Canada, however, Loran-C transmitters were switched off last year. After a long debate about the merits of keeping the system going, Barack Obama declared it outdated. The House of Representatives has given the Department of Homeland Security until April to decide whether a single, national GPS backup system is required. Which technology would be used to build such a system remains to be seen.

In a way, GPS has become a victim of its own success. Because it is used for such a wide range of civilian purposes, when somebody wishes to disable one GPS-based system, their actions can also disrupt other, unrelated systems. The benefits of satellite positioning are undeniable, and they are only likely to increase in future. But it is now clear that fully realizing those benefits depends on putting systems in place to mitigate against deliberate and accidental interference, and to provide an independent backup that does not rely on the delicate trilling of distant satellites. 

GPS jamming affects everyone, even the London Stock Exchange

As reported by The Economist: Every day for up to ten minutes near the London Stock Exchange, someone blocks signals from the global positioning system (GPS) network of satellites. Navigation systems in cars stop working and time-stamps on trades made in financial institutions can be affected. The incidents are not a cyber-attack by a foreign power, though. The most likely culprit, according to Charles Curry, whose firm Chronos Technology covertly monitors such events, is a delivery driver dodging his bosses’ attempts to track him.

The signals are weak. Mr Curry likens them to a 20-watt light bulb viewed from 12,000 miles (19,300 km). And the jammers are cheap: a driver can buy a dashboard model for about £50 ($78 USD). They are a growing menace. The bubbles of electromagnetic noise they create interfere with legitimate GPS users. They can disrupt civil aviation and kill mobile-phone signals, too. In America their sale and use is banned. In Britain they are illegal for civilians to use deliberately, but not, yet, to buy: Ofcom, a regulator, is mulling a ban. In recent years Australian officials have destroyed hundreds of jammers.

In the right (or wrong) hands, they are potential weapons. Britain’s armed services test the devices in the Brecon Beacons in Wales, a military training area. North Korea uses big lorry-mounted versions to block GPS signals in South Korea. Starting with a four-day burst in August 2010, the attacks, which come from three positions inside the North, have lengthened. In early 2012 they ran for 16 days, causing 1,016 aircraft and 254 ships to report disruption.

North Korea GPS jamming systems

Mr Curry worries that criminals or terrorists could knock out GPS for an entire city or shipping lane anywhere in a flash. Even without North Korean-sized contraptions, the jamming can be substantial. Suitcase-sized devices on sale on the internet claim a range of 300-1,000 metres.

Malfunctioning satellites and natural interference from solar activity have hit GPS signals and sent ships off course. David Last, a navigation expert, says an accidental power cut, perhaps caused by a jammer taken on board a car ferry, could cause a shipwreck. Generating a false signal—spoofing—is another threat. In December 2011 Iran said it had spoofed an American drone before capturing it (most experts dismiss the claim). So far effective spoofing seems confined to laboratories, but Mr Last says some governments are already taking countermeasures.

One solution is a different means of navigation. In April South Korea announced plans for a network of 43 eLoran (enhanced long-range navigation) ground-based radio towers, based on technology first used in the second world war. It uses a far stronger signal than GPS, and should give pilots and ships’ captains a safer alternative by 2016. With Chinese and Russian help, South Korea hopes to expand coverage across the region.

Britain’s General Lighthouse Authorities (GLA) are following suit with seven new eLoran stations. Martin Bransby, an engineer with the GLA, says this will replace visual navigation as the main backup for GPS. It will be working by mid-2014, and cost less than £700,000 ($1.08M USD); receivers cost £2,000 ($3,077 USD) per vessel. By 2019 coverage should reach all big British ports.

America’s military-research agency DARPA has an experimental “single-chip timing and inertial measurement unit” (TIMU). When finished, according to the project’s boss, Andrei Shkel, it will use tiny gyroscopes and accelerometers to track its position without using satellites or radio towers. America’s White Sands missile range in New Mexico is installing a “Non-GPS Based Positioning System”, using ground-based antennae to provide centimeter-level positioning over 2,500 square miles. In May the Canadian government said it would splash out on anti-jam upgrades for military aircraft.

A new version of the US air force’s bunker-busting bomb, designed in part to destroy Iranian nuclear facilities, includes technology to prevent defenders from blocking its satellite-based guidance systems. MBDA, a European missile firm, is working on similar lines.

But for many users, GPS and other space-based navigation systems—which include Russia’s GLONASS, China’s partly complete Beidou, and an as-yet unfinished project by the European Union (Galileo)—remain indispensable and ubiquitous. They are also vulnerable. For those whose lives or livelihoods depend on knowing where they are, more resilient substitutes cannot come fast enough.

Hybrid location technologies: MEMS Sensor Positioning

Most smart phones include several MEMS sensors. The data they provide
helps make location possible when GPS signals are compromised.

As continued from our previous report: Many smart phones are equipped with sensors that track device orientation and movement to enable a host of applications, such as gaming and compasses (Table 6). These sensors usually include microelectromechanical systems (MEMS).

For example, accelerometers measure acceleration based on user movement. Generally, a three-axis accelerometer measures the change in user velocity position in a variety of cases, such as walking, running, falling, and vibration.

Gyroscopes measure rotational velocity. They also are implemented across three axes. Gyroscope measurements provide orientation. A combination of accelerometer and gyroscope measurements in three dimensions can be used to continuously track user position.

Magnetometers measure the earth’s magnetic field as well as any ambient magnetic influences. They are used for mapping and compass functions (potentially in conjunction with accelerometers). And, barometers measure the altitude based on air pressure changes and can be used to find a user’s position while moving up in altitude (Fig. 4).

Physical readings from the sensors are typically sent to the inertial measurement unit (IMU), which collects data from the inertial sensors, formats them, and delivers them to the sensor location subsystem—the inertial navigation solution (INS). Yet there’s a key difference in the positioning technique used by the INS compared to other location methods.

A-GNSS and Wi-Fi positioning and cellular positioning methods feature an absolute position computation process. The INS uses dead reckoning. It’s given a starting position (perhaps from an A-GNSS fix) and then uses sensor data such as speeds and angular direction to advance the position over time. Eventually, the uncertainties in the reported sensor data add up, and a new, accurate reference position is required to start the dead reckoning process over.

While GPS, Wi-Fi, and cellular technologies provide the user’s position on the map, sensors can provide an idea of how the mobile device itself is moving—whether it’s being turned, set on a table, or thrown. This fine-grade information can be very useful for enabling applications such as gaming. It also presents a challenge.

If purely position calculation is of interest, then the positioning engine must be able to intelligently filter out extraneous effects such as the rhythmic motions of walking or running and holding the handset in different positions while talking. Different people have different usage profiles, so the sensor’s positioning engine must be able to robustly handle a variety of different scenarios.