Positioning: A Brief History PDF

Positioning: A Brief History - History of Positioning 1 Learning Objectives In this lecture you will learn… • Why positioning was important in the past and why it’s still important today • How the concepts of positioning have developed through time and have resulted in the technology we currentl...

Positioning: A Brief History - History of Positioning 1 Learning Objectives In this lecture you will learn… • Why positioning was important in the past and why it’s still important today • How the concepts of positioning have developed through time and have resulted in the technology we currently use • Principles behind the space technology we currently use today to locate ourselves History of Positioning 2 Introduction and Definitions A position can be determined in two different ways: • Relative • To other landmarks or features • Absolute • Coordinates of a point in space To obtain an absolute position requires sophisticated equipment and precise measurements History of Positioning 3 Relative vs. Absolute Positioning • Describe your current location using: • Relative positioning • Absolute positioning History of Positioning 4 Jericho beach position: relative versus absolute positioning @ Googlemaps Which definition is absolute and which is relative ? History of Positioning 5 Positioning in the Pre-Space Era • Astronomy, navigation, surveying and geodesy were based on similar instruments and methods • Historically, the most important practical application of positioning was to provide safe ocean navigation Triangulation to measure a comet trajectory, 1532 @ Wikimedia Commons History of Positioning 6 Triangulation Based on the trigonometric rule that if one side and two angles of a triangle are known, the remaining sides can be computed By measuring • Angles – triangulation • Distances – trilateration Imagine a distant mountain peak (the star) and two observers are located at 'A' and 'B' separated by a few kilometers (the length 'S'). The base angles at A and B can be measured with an instrument called a theodolite. By knowing the base distance A to B, and the angles the distance to the peak can be worked out using triangulation. Triangulation @ Spacemath, NASA History of Positioning 7 Measuring Angles: Theodolites - E Theodolite • surveying instrument of high precision • measure both vertical and horizontal angles History of Positioning Theodolite, 1860 @ Wikimedia Commons 8 Geodetic network • The first geodetic survey was undertaken in France at the end of the 17th and early 18th century • By the end of the 19th century, major geodetic networks covered the United States, Canada, India, Great Britain, and large parts of Europe Nautical chart of the Atlantic Ocean, 1693 @ Wikimedia Commons History of Positioning 9 Geodetic network • The geodetic points are the historical basis for the mapping of the Earth’s surface • It provides a number of fixed stations whose relative and absolute positions are accurately established • These points can then be used to calculate other points by using triangulation Geodetic point @ Wikimedia Commons Triangulation versus trilateration @ Wikimedia Commons History of Positioning 10 • 9 years in jail if you tamper with them History of Positioning 11 Geodetic network in Poland Geodetic point in US @ Wikimedia Commons Geodetic network in Poland @ Geodezja History of Positioning 12 Ocean navigation • Navigation on the ocean was very problematic • Navigation methods using Relative positioning: • Pilotage • Dead reckoning Absolute positioning: • Celestial navigation & marine chronometer The Noord-Nieuwland in Table Bay, 1762 @ Wikimedia Commons History of Positioning 13 Pilotage • First method of navigation used • Before 15th century or in coastal navigation, within sight of land • Based on visual triangulation to known landmarks • No need for accurate position, but that one is in a safe position or on a safe line • Generally helped by maps or nautical charts Nautical chart of Fernao Vaz Dourado, 1571 @ Wikimedia Commons History of Positioning 14 Dead Reckoning • First method of navigating on the open sea • Used from 15th to 17th Century • Calculate position by using a previously determined position, and advancing that position based upon estimated speed over time • Fairly accurate at short distances • Requires very precise information on speed and direction over long distances -> cumulative errors Pedro Alvares Cabra discovery of Brazil, 1500 @ Wikimedia Commons History of Positioning 15 Celestial Navigation • Dead reckoning errors accumulate over long voyages • So navigators sought other reference points on the sea • Most found that: • Part of the solution was in the sky • While part of the solution relied upon time History of Positioning 16 Calculating Latitude • The night sky changes for most of us on a daily and seasonal scale • The daily rotation of the Earth causes stars to sweep through the sky • The seasonal revolution of the Earth around the sun changes our perspective • i.e. The direction you face during night time changes History of Positioning 17 Estimating Latitude • To measure latitude we can point to: • North star in northern hemisphere • The North Star is nearly directly above the north pole • No matter what time of year or day, the North star is always directly above the north pole • The angle to the North Star directly measures your latitude Quadrant description @ Wikimedia Commons History of Positioning 18 Longitude Challenge • Longitude was much harder • And resulted in many ship wreaks • For decades no one was able to come up with a practical solution to the problem • Some searched for the solution in the skies, others in building a precise clock… Ships in Distress off a Rocky Coast, 1667 @ National Gallery of Art, Washington History of Positioning 19 The Longitude Challenge • The key to calculating longitude is time • The distance from a line of longitude to the prime meridian can be measured in hours and minutes • The Earth revolves once on its axis every 24 hours at the equivalent of 1° of longitude in four minutes, or 15° an hour • The comparison of time between a known place (e.g. Greenwich) and the local time would determine longitude Calculating longitude with a marine chronometer @ National Air and Space Museum, Smithsonian Institution History of Positioning 20 Clock The Marine Chronometer - • John Harrison came up with his H4 chronometer design in 1761 John Harrison, 1767 @ Wikimedia Commons History of Positioning 21 The Marine Chronometer • Requires that an observer knows exact Greenwich Mean Time (GMT) at the medim -> moment of observation prive • Every four seconds of time error, the position measurement will be off by approximately one nautical mile Marine chronometer @ Wikimedia Commons History of Positioning 22 Where Am I? Lecture 4: History of Positioning 23 Space – New navigation frontier • Navigators have looked to the sky for direction for thousands of years • Since 1957, celestial navigation has simply switched from natural objects to artificial satellites • Navigation satellites are like orbiting landmarks • If the satellite orbit is known, location on the earth can be determined with at least 4 satellites Navigation satellites constellation @ Wikimedia Commons usive Practice Questions ↑ landmarks features . of - the Lacation to describe urplace compared coordinate - to them • What is the difference between relative and absolute position? • What is the difference of longitude represented by 12 hours difference in local time (using a marine chronometer)? 180 • Which methods of historical positioning use absolute positioning and which use relative positioning? • Why is latitude easy to determine with celestial navigation (at least for the Northern Hemisphere)? : d not SMae ocean ! North star is and bright very doesn't more . is always in no exact care position time the matter what25 year of Additional material • Dava Sovel, 1995. Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. http://www.amazon.ca/LongitudeGenius-Greatest-Scientific-Problem/dp/080271529X • Fritz E. Uttmark, 1919. Marq Saint-Hilarie method: for finding a ship's position at seahttp://www.amazon.ca/Marc-St-Hilaire-methodposition/dp/B003QMMJXA • Willis E. Johnson, 1907. Mathematical geography. https://archive.org/details/mathematicalgeo00johngoog • Institute of navigation. Navigation educational materials. https://www.ion.org/outreach/lesson-plans.cfm History of Positioning 26 References • National Air and Space Museum, Smithsonian Institution. http://timeandnavigation.si.edu/navigating-at-sea • Introduction to marine navigation. http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-01.pdf • Navigation principles of positioning and guidance. http://www.springer.com/us/book/9783211008287 • A study of navigation and seafaring in the fifteenth century. https://circle.ubc.ca/handle/2429/1901 • James A Van Allen. Basic principles of celestial navigation. http://libvolume6.xyz/nauticalscience/bsc/semester5/principlesofnavigationp aper3/principlesofnavigation/principlesofnavigationnotes1.pdf • Geodetic surveys. • http://www.history.noaa.gov/stories_tales/geodetic1.html History of Positioning 27 References • National Air and Space Museum, Smithsonian Institution. http://timeandnavigation.si.edu/navigating-at-sea • Introduction to marine navigation. http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-01.pdf • Navigation principles of positioning and guidance. http://www.springer.com/us/book/9783211008287 • A study of navigation and seafaring in the fifteenth century. https://circle.ubc.ca/handle/2429/1901 • James A Van Allen. Basic principles of celestial navigation. http://libvolume6.xyz/nauticalscience/bsc/semester5/principlesofnavigationp aper3/principlesofnavigation/principlesofnavigationnotes1.pdf • Geodetic surveys. • http://www.history.noaa.gov/stories_tales/geodetic1.html History of Positioning 27