Indoor Positioning

Technologies and Performance

Nel Samama

• Publisher: Wiley-IEEE Press
• Year: 2019
• ISBN:
  9781119421863
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Elaborazione di segnali

Provides technical and scientific descriptions of potential approaches used to achieve indoor positioning, ranging from sensor networks to more advanced radio-based systems

This book presents a large technical overview of various approaches to achieve indoor positioning. These approaches cover those based on sensors, cameras, satellites, and other radio-based methods. The book also discusses the simplification of certain implementations, describing ways for the reader to design solutions that respect specifications and follow established techniques. Descriptions of the main techniques used for positioning, including angle measurement, distance measurements, Doppler measurements, and inertial measurements are also given.

Indoor Positioning: Technologies and Performance starts with overviews of the first age of navigation, the link between time and space, the radio age, the first terrestrial positioning systems, and the era of artificial satellites. It then introduces readers to the subject of indoor positioning, as well as positioning techniques and their associated difficulties. Proximity technologies like bar codes, image recognition, Near Field Communication (NFC), and QR codes are covered—as are room restricted and building range technologies. The book examines wide area indoor positioning as well as world wide indoor technologies like High-Sensitivity and Assisted GNSS, and covers maps and mapping. It closes with the author's vision of the future in which the practice of indoor positioning is perfected across all technologies. This text:

• Explores aspects of indoor positioning from both theoretical and practical points of view
• Describes advantages and drawbacks of various approaches to positioning
• Provides examples of design solutions that respect specifications of tested techniques
• Covers infra-red sensors, lasers, Lidar, RFID, UWB, Bluetooth, Image SLAM, LiFi, WiFi, indoor GNSS, and more

Indoor Positioning is an ideal guide for technical engineers, industrial and application developers, and students studying wireless communications and signal processing.

1
A Little Piece of History …

Abstract

In this chapter, we briefly look back at the evolution of geographical positioning. Our intention is to show that indoor positioning is indeed a very recent need that has come about due to the spread of modern mobile‐connected terminals and owners wanting to receive numerous so‐called services, many of which are greatly enhanced when associated with the user location. The benefit of many of them is 10‐fold when associated with the user location. Thanks to the Global Positioning System, the famous GPS, this association was made possible in the early 1990s. Unfortunately, this fantastic system has been unable to meet the performance required indoors, where a “typical” urban citizen spends the majority of his or her time (The term “typical” will appear sometimes in the book. Although experience has shown such “typical” persons, objects, or environments do not exist, we will use this term to appoint a classical situation).

Keywords: History; longitude problem; navigation; clocks; Harrison;

As soon as human beings decided to explore new territories, or even just to move within new territories, they needed a way to locate themselves in their environment.

1.1 The First Age of Navigation

The origins of navigation are as old as man himself. The oldest traces have been found in Neolithic deposits and in Sumerian tombs, dating back to around 4000 years CE The story of navigation is strongly related to the history of instruments, although they did not have a rapid development until the invention of the maritime clock, thanks to John and James Harrison, in the eighteenth century. The first reason that pushed people to “take to the sea” is probably related to both the quest for discovery and the necessity of developing commercial activities. In the beginning, navigation was carried out without instruments and was limited to “keeping the coast in view.” It is likely that numerous adventurers lost their lives by trying to approach what was “over the horizon.”

The astronomical process used for positioning was quite inaccurate, and hence, frequent readjustments were required. The localization was even more complex because of the lack of maps. Nowadays, the situation of indoor positioning is in the same state: accuracy is not at the desired level, and frequent readjustments are needed. Moreover, one of the most important problems is the lack of indoor maps allowing navigation (i.e. not just an image). This very hot topic is dealt with in Chapter 13.

Unfortunately, astronomical positioning was only able to give the latitude of the point, as can be understood from Figure 1.1. The longitude problem would remain unresolved for centuries: will it be the same for indoor positioning?¹

Figure 1.1 Determining latitude with the pole star.

A first remark can be made at this stage: positioning at the epoch was not continuous in time and space, contrary to what we are looking for today. However, is it really essential indoors?

1.2 Longitude Problem and Importance of Time

The so‐called longitude problem was much more difficult to solve and took almost three centuries. During this period, significant progress occurred concerning instruments and maps, but nothing for determining the longitude. As early as 1598, Philipp II of Spain offered a prize to whoever might find the solution. In 1666, in France, Colbert founded the “Académie des Sciences” and built the Observatory of Paris: one of his first goals was to find a method to determine longitude. King Charles II also founded the British Royal Observatory in 1675 in Greenwich to solve this problem of finding the longitude at sea. Giovanni Domenica Cassini, a professor of astronomy in Bologna, Italy, was the first director of the French academy and in 1668 proposed a method of finding the longitude based on the observations of the moons of Jupiter: this work followed the observations made by Galileo² concerning these moons using an astronomical telescope. It had been known from the beginning of the sixteenth century that the time of the observation of a physical phenomenon could be linked to the location of the observation; thus, knowing the local time where the observations were made compared to the time of the original observation (carried out at a reference location) could give the longitude. Cassini established this fact with the moons of Jupiter after having calculated very accurate ephemeris. Unfortunately, this approach needs the use of a telescope and is not practically applicable at sea.

On 11 June 1714, Sir Isaac Newton confirmed that Cassini's solution was not applicable at sea and that the availability of a transportable timekeeper would be of great interest. It has to be noticed that Gemma Frisius also mentioned this around 1550, but it was probably too early. On 8 July 1714, Queen Anne offered, by Act of Parliament, a £20 000 prize³ to whoever could provide longitude to within half a degree. The solution had to be tested in real conditions during a return trip to India (or equivalent), and the accuracy, practicability, and usefulness had to be evaluated. Depending on the success of the corresponding results, a smaller part of the prize would be awarded.

The development of such a maritime timekeeper took decades to be achieved but finally had an impact on far more than navigation. The history of Harrison's clocks is quite interesting, and time is really the fundamental of modern satellite navigation capabilities. We have seen that Isaac Newton himself confirmed that the availability of a transportable maritime clock would be the solution to the longitude problem: the realization of such a clock, however, was not so easy. The main reason is that the clock industry was fundamentally based on physical principles dependent on gravitation (the pendulum). This was acceptable for terrestrial needs, but of no help in keeping time when sailing. Thus, a new system had to be found.

The reason that time is of such importance is because of the Earth's motion around its axis. As the Earth makes a complete rotation in 24 hours, it means that every hour corresponds to an eastward rotation of 15°. Thus, let us suppose that one knows a reference configuration of stars (or the position of the sun or the moon) at a given time and for a given well‐known location (e.g. Greenwich). If you stay at the same latitude, then you will be able to observe the same configuration but at another time (later if you are eastward and earlier if westward): the difference in times directly gives the longitude, as long as the time of the reference location (Greenwich in the present example) has been kept. The longitude is simply obtained by multiplying this difference by 15° per hour, eastward or westward. The method is very simple and the major difficulty is to “keep” the time of the reference place with a good enough accuracy, i.e. with a drift less than a few seconds per day. Pendulums, although of good accuracy on land, were unable to provide this accuracy at sea, mainly because of the motions of the ship and changes in humidity and temperature.

John Harrison built four different clocks, leading to numerous innovative concepts. After almost 50 years of remarkable achievements (August 1765), a panel of six experts gathered at Harrison's house in London and examined the final “H4” watch. John and William (his son) finally received the first half of the longitude prize. The other half was finally awarded to them by the Act of Parliament in June 1773. Certainly more important is the fact that John Harrison was finally recognized as being the man who solved the longitude problem.

One of the most famous demonstrations of Harrison's clocks' efficiency was given by James Cook during the second of his three famous voyages in the Pacific Ocean. This second trip was dedicated to the exploration of Antarctica. In April 1772, he sailed south with two ships: the Resolution and the Adventure. He spent 171 days sailing through the ice of the Antarctic and decided to sail back to the Pacific islands. He returned to London harbor in June 1775, after more than 40 000 nautical miles. During this voyage, he was carrying K1, Kendall's copy of Harrison's H4. The daily rate of loss of K1 never exceeded eight seconds (corresponding to a distance of two nautical miles at the equator) during the entire voyage: this was the proof that longitude could be measured from a watch.

Indoor positioning is almost in the same situation as that of the longitude determination in the early eighteenth century: it seems to be quite close, but there is indeed no satisfactory solution. Hopefully, it will take less than 50 years to find an acceptable approach.

1.3 Link Between Time and Space

The perception of time has changed quite a lot over the centuries until the current omnipresent availability of a precise time that can thus be shared by everybody. By briefly analyzing the evolution of the effects of this availability of time on people's life, some parallels are drawn concerning possible changes induced by the availability of positioning.

1.3.1 A Brief History of the Evolution of the Perception of Time

At the very beginning, time and space were notions that people felt: the number of days of walk needed to reach a g...