Literature Review: Pedestrian Inertial Navigation

Introduction

History of navigation can be traced back beyond Western civilization to Phoenicians more than 4,000 years ago when primitive systems and charts were used to determine the position at the sea in relation to the Sun and stars. Before 15th Century, marine sailing was essentially limited to the coastal sea (open sea) with predictable winds and currents and continuous continental shelf to use as a guide. According to Blake (2009) and Hasan (2017), the earliest navigational tools made the use of recorded voyages routes leading to creation of nautical charts though limited by missing latitude and longitude labelled it had a compass rose showing the mariners the direction to follow. Navigation has significantly improved with emerging civilization including adoption of the internet and GPS to enhance further the process of navigation.

Navigation system

A navigation system can be defined as a system or instrument that aids in the process of accurately identifying ones position within the earth’s surface as well as being able to plan and follow a specific route to a desired destination otherwise known simply as navigation. There are a wide range of navigation systems made of a combination of different elements including vessels, stationary positions, and communication processes. According to Rouse (2018) a navigation system is simply an instrument that has the capability of determining ones current position and aids them in the determination of the distance and direction of their intended destination. In the current age most navigation systems use Global Positioning Satellite (GPS) in the determination of individual or vessel positioning, comparing it with a sought after destination and guiding it through the most efficient route (Rouse, 2018).

Capabilities of navigation Systems

However, a navigation system is capable of much more than just pinpointing location and direction as highlighted by Groves et al (2007), some of these other capabilities include: determination of a vehicle or other objects location via sensors, maps and other external sources, containing maps which are displayed in the various devices and are capable of being read and deciphered by humans in further enhancing positioning and direction, they provide suggested directions which are most efficient in terms of distance and route efficiency to the controller of a vessel via text or speech. The systems are also capable of providing information on nearby vessels or vehicles or any other obstacles or hazards, providing information on traffic conditions within a particular rout and offering suggestions on other effective alternatives.

Types of Navigation Systems

A wide range of types of navigation systems are highlighted by Groves et al (2007) including: Marine navigation, automotive navigation, Robotic mapping, Satellite navigation, surgical navigation systems as well as inertial guidance systems. All these systems however are based on either one of three navigation ways which are highlighted by Bemis (2017) to include: Celestial Navigation, Global Positioning Satellite and Orienteering.

Orienteering

Orienteering is an old fashioned navigation which Bemis (2017) highlights to involve finding ones position and way through a defined course with checkpoints using a map and a compass only. This highlights the very basic means and system of navigation which utilizes simple non electronic tools in a map and a compass. While the map highlights the general picture of the space the compass is used to pinpoint direction of intended destination. The limitation of this type of navigation systems is that one travels to a destination oblivious of exactly how far it is from their current position.

Celestial Navigation

This is a navigation system mostly used in ancient historical times especially by the Phoenicians, Bemis (2017) clarifies that this navigation system is the art and science of navigation by the use of the sun, stars, moon and other planets practiced by humans in the ancient times. Its concept is similar to basic triangulation that uses the positioning of two celestial bodies and an instrument called a sextant which measures the angle of the body above the horizon (Machtelinckx, 2018). By adjusting ones height above sea level and using of charts arranged by time, a location line can be determined. Repeating the same process with a second body enables the drawing of two lines whose intersection provides the location of destination. This type of navigation system was more common in ancient times with lack of compasses. More recently however it was more commonly used in sea travels where there are no landmarks to guide on direction. A limitation however is that the system is only usable if one can be able to view celestial bodies without which it becomes impossible.

Global Positioning Satellite

GPS or Satellite navigation on the other hand is based on a global network of satellites that transmit radio signals in medium earth orbits. The system consists of 32 globally positioned satellites which emit signals to receivers in the earth surface and determining their location by computing the difference between the time that a signal is sent and received. The signal contains data that is used by the receiver to compute the locations of the satellite and make any adjustments required for accurate positioning (Faa.gov, 2018).With information about the ranges of three satellites which the receiver has received signals from and calculated their distance and location, the receiver can then be able to compute its own three dimensional positioning. While an atomic clock synchronised with the GPS is required to be able to compute ranges from the three satellites by the receiver, Rouse (2018) highlights that addition of measurements from a fourth satellite eliminates the need for the atomic clock. According to Bemis (2017) GPS provides users with Positioning, Navigation and Timing (PNT) services whether on land or on sea, highlighting a most efficient technique of navigation in the current century. It encompasses three segments as highlighted by (Rouse, 2018; Bemis, 2017; Faa.gov, 2018), these include: the space segment, the control segment and the user segment. The space segment includes the 32 satellites orbiting the planet twice everyday and is a responsibility of the U.S Air force. The satellites arrangement across the planet is optimized to maximize radio signals to users in the widest range possible. The control system consists majorly of a master control station, a monitoring station and grounded antennas. The control segment is essential for the process of monitoring and transmission of signals between the different satellites and users. The user segment involves the GPS technology available in everyday devices used by humans including, vehicles, cell phones and watches. However GPS is also used in weather forecasting, farming, and extensive military applications as well as in survey and construction (Bemis, 2017). Faa.gov (2018) however highlights among the well known GPS limitations to include a limited accuracy of approximately 7.8 metres 95% of the time. Goodman (2019) further clarifies that inaccuracy can be caused by obstructions of the satellite signals with objects such as walls, skyscrapers, trees as well as extreme atmospheric conditions. In addition physical features especially in urban areas are quite dynamic as such the map and mapping technology used in conjunction with the GPS may be outdated further enhancing inaccuracy. These limitations of satellite based positioning, especially in constrained environments such as urban areas and indoors are complemented by a wide range of spectrum in the current

industrial revolution including inertial Sensors and inertial systems which enable the location of individuals without infrastructure.

Pedestrian Inertial Navigation Systems

The pedestrian inertial navigation system involves a navigation system that uses inertial sensors in being able to pin point the location of an individual. The pedestrians location is estimated based on inertial measurements, by the use of the pedestrians step length or overall distance travelled calculated by inertial sensors which are either mounted on the foot or belt of the pedestrian. The new location of the pedestrian can be located by manipulating distance and angle of travel from these sensors and thus aiding the accurate determination of position. The Inertial Navigation System according to Yang et al. (2017) refers to an infrastructure free navigation system that uses inertial sensors such as accelerometers and gyroscope which do not require external references and/or installations beforehand. One such example and the one that I actually use include the MATLAB mobile and computer application which uses other mobile applications linked to it to measure 3D acceleration, latitude, longitude and other required measures. Modern technology such as the development of micro-electromechanical system inertial measurement unit (MEMS-IMU) has enabled the development of portable, small sized, lightweight, inexpensive inertial sensors with low power consumption that impact pedestrian Inertial navigation systems. These sensors are even available within modern upgraded smart phones and as such normal Smartphone users can be able to use them in the navigation of urban canyons. The sensors could however be independent devices as well in which instance they can be mounted on any part of the pedestrians’ body, most often the foot or the belt. Dekhordi et al. (2014) further emphasize that the system is developed using a gyroscope and accelerometer significantly leaving out the magnetometer to enhance its insensitivity of to the presence of metals and magnetic fields therefore be able to estimates the users trajectory with the same accuracy both in indoors as well as outdoor environments. Groves et al (2007) however point out that there are a number of different approaches to the use of the inertial sensors and are generally dependent on: The number as well as quality of the inertial sensors being used, whether or not to mount them on the shoes or the body, as well as whether to utilize conventional inertial navigation algorithms supported by Pedestrian dead reckoning or Zero Velocity Updates, or both.

A foot mounted inertial Navigation system uses three axis accelerations and angular rates to calculate the exact position of an individual after which the route can then be defined. Patarot et al. (2014) highlights that the principle of Inertial Navigation systems is that: the integration of acceleration is velocity, while the integration of velocity becomes position. When these sensors are attached on the foot the overlapping strides impacts the accumulation of drift overtime leading to a huge positioning error, however Dekhordi et al. (2014) highlight the application of the Zero Velocity Update (ZUPT) algorithm which is based on the status of the left and right foot impacts in the minimization of the error and enhancing accuracy. However a recently developed belt mounted Inertial Navigation System aims to facilitate the equipment and the mobility of the users while at the same time maintaining repeatable performances. Patarot et al (2014) emphasizes the average error in position to be less than 2% in a travelled distance of about 200 metres making the belt mounted INS as much efficient as the foot mounted INU. Other considerations in the inertial navigation system include the classification systems.According to Park and Suh (2010) different classes of error are eminent depending on the location of the sensors in the body as well as the different classifications of pedestrian movement including: jogging, walking, running or climbing up or down a stairs way.

Park and Suh (2010) points out that the inertial navigation algorithm in Zero Velocity Update impacts the detection of zero velocity intervals and serves to reliably reset the error. In instances of walking and running the velocity is reliably updated to calculate distance and therefore enhance the process of positioning. In the process of climbing up and down a stair on the other hand, while the speed and distance travelled may be recorded on the high the latitude and longitudes fail to change and thus the determination of positioning is entirely dependent on the other aspects attached to the sensors. This is particularly useful when using sensors on smart phones and computers where they can be integrated with other navigation applications. One of the limitations of using Inertial Navigation systems however include the consideration and accounting for pedestrian negative movements. According to Ngo et al (2018) negative pedestrian locomotion includes movements that a user can naturally make without any real position displacement. However sensor signals may misidentify these movements as steps and integrate them into the calculation thereby leading to the development of an error in accuracy. The use of the Inertial Navigation Systems in the real world in addition is limited given the sensors susceptibility to noise and gradual drifts which eventually have the impact of causing cascading errors. Martin et al (2006) however highlight that most of these systems integrate the use of known positions with the use of satellite and wifi routers in calculating the position of the mobile device and consequently minimize the inaccuracies. Other challenges include: the need of the Long initial alignment time of the device at any time before its use and in addition the time information cannot be given using the INS.

Conclusion

The shortcomings of the GPS navigation systems as well as the fourth industrial revolution have impacted the development of a relatively new in concept navigation system through the use of sensors and other wireless devices. The Pedestrian Inertial Navigation system is quite essential in the determination of accurate locations and often used to compliment the Global Positioning Satellite in the determination of an individual or vessel locations especially in constrained environments such as populated cities and indoors locations. Despite the various limitations and challenges it poses, it is a significantly accurate and reliable technique of navigation.

References

• Bemis, B. (2017). Outdoor Education School Science Camps California. [online] Outdoor Education in California. Available at: https://dirtyclassroom.com/3-types-of-navigation-barbara-bemis/ [Accessed 16 Apr. 2019].
• Blake, J. (2009). The sea chart: the illustrated history of nautical maps and navigational charts. Anova Books.
• Dehkordi MB, Frisoli A, Sotgiu E, Loconsole C (2014) Pedestrian Indoor Navigation System Using Inertial Measurement Unit. Sensor Netw Data Commun 2:115.
• Faa.gov (2018). Satellite Navigation - GPS - How It Works. [online] Faa.gov. Available at: https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/gps/howitworks/ [Accessed 16 Apr. 2019].
• Goodman, P. (2019). 7 Disadvantages of GPS Technology. [online] AxleAddict. Available at: https://axleaddict.com/safety/Disadvantages-of-GPS [Accessed 16 Apr. 2019]. Groves, P., Pulford, G., Littlefield, A. and Nash, D. (2007). Inertial Navigation Versus Pedestrian Dead Reckoning: Optimizing the Integration. International Journal of Sensor Networks and Data Communications, 6(3), pp.25-28.
• Hasan, H. (2017). A history of Persian navigation. Routledge. Machtelinckx, J. (2018). Celestial Navigation explained - page 1. [online] Onboardintelligence.com. Available at: http://onboardintelligence.com/CelestialNav/CelNav1.aspx?AspxAutoDetectCookieSupport=1 [Accessed 16 Apr. 2019].
• Ngo, C., See, S. and Legaspi, R. (2015). Improving Inertial Navigation Systems with Pedestrian Locomotion Classifiers. Proceedings of the 5th International Conference on Pervasive and Embedded Computing and Communication Systems.
• Patarot, A., Boukallel, M. and Lamy-Perbal, S. (2014). A case study on sensors and techniques for pedestrian inertial navigation. 2014 International Symposium on Inertial Sensors and Systems (ISISS).
• Rouse, M. (2018). What is GPS navigation system? - Definition from WhatIs.com. [online] WhatIs.com. Available at: https://whatis.techtarget.com/definition/GPS-navigation-system [Accessed 16 Apr. 2019]. Yang, W., Xiu, C., Zhang, J. and Yang, D. (2017). A Novel 3D Pedestrian Navigation Method for a Multiple Sensors-Based Foot-Mounted Inertial System. Sensors, 17(11), p.2695.

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