Geoapplications development http://rgeo.wikience.org Higher School - PowerPoint PPT Presentation

Geoapplications development http://rgeo.wikience.org Higher School of Economics, Moscow, www.cs.hse.ru

2 Signal-based positioning Satellite- based, WiFi e.g. GPS Beacons Cellular https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcSYYC7irjytoGY7XaURz3UeRCWkK_pcKVBCBhGKCCnZ64MG4CQo http://www.steelintheair.com/imgs/new-cell-tower-lease.jpg http://www.smbretail.com/wp-content/uploads/2015/12/tumblr_inline_ndeolbm5PR1rd9i5u.png

GPS applications Tracking of birds and animals Osprey (blue), Marsh Harrier (green), Egyptian Vulture (orange), Short-toed Eagle (red). http://dx.plos.org/10.1371/journal.pone.0039833;jsessi

GPS applications CYGNSS – Cyclone Global Navigation Satellite System Innovation: retrieve wind speed of tropical cyclones in presence of clouds + with high frequency Launched in 2016: https://www.nasa.gov/cygnss

GPS applications Precision gunfire The most advanced Tomahawks fly at 550 mph, have GPS, onboard digital maps, video cameras, two- way satellite links and a navigation system that allows them to loiter over an area and wait for their targets to pop up. That's in addition to the 1,000- pound bomb each Tomahawk typically carries. http://www.nbcnews.com/technology/how-tomahawk-cruise-missiles-send-message-syria-8C11022222

GPS applications Precision agriculture The precision farming integrated solution includes suite of GPS and GIS enabled applications which together are being used for farm planning, field mapping, soil sampling, tractor guidance, crop scouting, variable rate applications, and yield mapping. https://www.gps4us.com/news /post/Global-positioning-and- geographic-information- systems-help-create-an- environmentally-friendly-farm- 20111228.aspx

GPS applications Railway Positive Train Control (PTC) systems prevent collisions, derailments, work zone A PTC system can automatically vary train speeds, incursions, and passage re-route traffic, and safely direct maintenance through switches in the crews onto and off tracks. PTC increases track wrong position. capacity by maintaining a constantly updated operating plan that optimizes rail use and flow. http://www.gps.gov/applications/rail/

8 GPS – Global Positioning System 1. Orbital segment http://image.slidesharecdn.com/pgdgi03semin arnavdeepsingh-140113095137- 2. Control segment phpapp02/95/global-positioning-system-7- 3. User segment 638.jpg?cb=1389607822

9 GPS – Orbital Segment Orbital segment: 21 satellites + 3 backup are sufficient to provide the global coverage. Currently 31 GPS satellites orbiting the Earth. The image shows 4 planes * 6 satellites http://www8.garmin.com/graphics/24satellite.jpg

10 GPS satellite visibility Minimum number of GPS satellites visible over 1 day, January 1, 2010 http://blogs.agi.com/navigationAccuracy/?p=315

11 GPS satellite visibility Number of visible satellites https://upload.wikimedia.org/wikipedia/commons/9/9c/ConstellationGPS.gif

12 GPS – Ground Segment Also called control segment or ground stations: 1. a master control station (MCS) 2. an alternate master control station 3. four dedicated ground antennas 4. six dedicated monitor stations Satellites carry precise atomic clocks with nanoseconds accuracy. The responsibility of a control segment is to periodically send current precise time and location to each satellite. Ephemeris – position of a satellite at a given time.

13 GPS – User Segment Cheap and small receivers One of the key differences between receivers is accuracy. Advanced equipment and advanced receivers increase accuracy . http://www.ainonline.com/aviation-news/aviation-international-news/2012-05-02/gps- jamming-prompts-renewed-interest-system-backup

14 GPS positioning in 2D: (lat, lon)

15 GPS positioning – 4 satellites for 3D (lat, lon, z) This and previous illustrations are idealized (the case of having exact distance between receiver and transmitter). https://openclipart.org/image/2400px/svg_to_png/191659/GPS-3D-trilateration.png

16 GPS math Distance between satellite and receiver = wave speed * time • wave speed = speed of light = 186K miles/sec • time? o Satellite generates the pseudo-random sequence and transmits it to receivers o Receiver generates the same sequence as well o After the sequence has arrived, receiver aligns it with its own sequence and finds time shift https://openclipart.org/image/2400px/svg_to_png/191659/GPS-3D-trilateration.png

17 GPS drawbacks: errors http://www.iranmap.com/wordpress/wp-content/uploads/2010/04/gps-errors.jpg

18 GPS drawbacks: satellite visibility There are cases when less than 4 satellites may be visible at a time One of the ways around: add more satellites Other drawbacks – indoor navigation impossible, canyon effects (this image), slow (in cold receiver state), high battery power consumption, low accuracy in some cases http://www.geo.upm.es/postgrado/CarlosLopez/materiales/cursos/www.ncgia.ucsb.edu/educat ion/curricula/giscc/units/u017/figures/figure15.gif

19 GLONASS Development started in Soviet Union, 1976 Now 28 satellites on orbit (not all are active – mainly due to backup purposes and maintenance) http://www.navigadget.com/wp-content/postimages/2011/11/glonass-map.jpeg

20 GPS & GLONASS & Co Several constellations increase sat. visibility . Global only are GLONASS – Russian GPS – US To be completed: Galileo – EU COMPASS – Chinese Now GPS receivers leverage satellite signals both from GPS and GLONASS Q: why are orbits so high? https://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/Comparison_satellite_navigation_orbits.svg/2000px- Comparison_satellite_navigation_orbits.svg.png

21 WiFi positioning Works for notebooks and other devices without GPS modules Works for indoor navigation Every network device is manufactured with a unique MAC Recall ARP (Address Resolution Protocol) On Windows type “ipconfig - all”

22 WiFi positioning Basic idea – create mapping MAC → (lat, lon) for all MACs Fingerprinting 1 Calibration (offline phase) – MAC, signal strengths, location 2 Positioning (online phase) – worse than GPS, better than cellular Accuracy ~ tens of meters

23 WiFi calibration Fingerprinting 1 Calibration (offline phase) – MAC, signal strengths, location (lat, lon) 2 Positioning (online phase) – worse than GPS, better than cellular • War driving collects fingerprints for all visible WiFi points • Volunteers, e.g. iPhones send fingerprint data anonymously to Apple Requires no password or other authentication information

24 WiFi calibration Databases store fingerprinting data However, they degrade over time https://en.wikipedia.org/wiki/Wi-Fi_positioning_system

25 WiFi positioning Fingerprinting 1 Calibration (offline phase) – MAC, signal strengths, location 2 Positioning (online phase) – worse than GPS, better than cellular The idea is similar to GPS; many algorithms exist to improve both phases http://www.mobizen.pe.kr/attach/1/cfile27.uf.146D33355047FEFD04B938.gif

26 Cellular positioning Less accurate, ~ hundreds of meters, order of magnitude higher than WiFi Same principles as in WiFi positioning http://www.swri.org/3pubs/ird2002/images/16-9222.jpg

27 Readings • • • • •

28 Practical task • • •