Extra credit available. Geography 12: Maps and Mapping. Getting to a Destination: Dead Reckoning. Lecture Outline

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1 Through a gross navigational error, the Love Boat steams into the Strait of Hormuz. The Strait of Hormuz is a strategic chokepoint between the Gulf of Oman and the Persian Gulf south of Iran Extra credit available Geography 12: Maps and Mapping Lecture 9: Navigation III: Marine Navigation and Electronic Aids to Navigation ucsb-geog.sona-systems.com Log on, create a user ID This helps make sure you get credit for what you re doing Study: Invisible objects Openings 9-5, Friday through Sunday Takes about 45 minutes. Alternative: 5 Article Summary Lecture Outline Finish Dead Reckoning and GPS Nautical Charts Traditional Aeronautical Charts Electronic Nautical Charts Intro to Raster & Vector Assisted Navigation Wayfinding Location Based Services Personal Guidance Systems Advantages & Disadvantages Getting to a Destination: Dead Reckoning Dead Reckoning is keeping track of position while moving by knowing direction and distance traveled (or speed & time) Requires Sure knowledge of starting position Careful record of movement, time, direction Accurate over short distances & easy to learn But errors accumulate, so not good over long distances 1

2 Dead Reckoning Plot Getting to a Destination: Terrain Association Divide trip into segments called legs Ease of recognition Ease of travel Move from one recognizable feature to another Can Combine with Dead Reckoning LORAN Long-Range Navigation (LORAN) Uses pairs of radio stations Transmit simultaneous pulses Differences in receipt time allow plotting of position Not useful for measuring very short distances Global Positioning Systems (GPS) GPS is a satellite-based navigation system 24 Satellites form the GPS Constellation (~31 now operational) Operated by the Department of Defense Costs about $400 million per year Free to use, just buy a receiver Works in all types of weather, but doesn t work well indoors First launch 1972, Declared Operational in 1994 Other Global Positioning Systems GPS is in common usage to describe the U.S. System Full U.S. Name is NAVSTAR GPS NAVigational Time And Ranging Other systems GLONASS Russia Galileo EU COMPASS China IRNSS - India Three Elements of GPS (1) Space 24 (~31 currently operating) orbiting satellites, plus more parked in space Satellites 20,200 km above ground (way out there) 5-10 satellites visible from any point Atomic clocks on board Transmit precise time (later used to calculate distance between observer and satellite) 2

3 Three Elements of GPS (2) Control Ground stations observe orbits, transmit corrections, synchronizing clocks Master control station located at Schriever AFB in Colorado Three Elements of GPS (3) User GPS Receivers Decode time Compare to local to determine time-delay (phase) This gives distance from each satellite Using Time Just like Harrison s Chronometer for determination of longitude, GPS uses time to calculate direction Delay x Speed of Light = Distance Since Distance is used, the method is trilateration Four Satellites Needed Two satellites provide a plane Three satellites narrow it down to two points Four points give latitude, longitude, and elevation If you know elevation, you can get by on three Accuracy in GPS Depends on quality of signal, # of satellites Likely error is calculated and presented Area instead of point Generally better than 10 meters On campus, 2-5m accuracy is common Error in GPS There are many reasons why more than four satellites are preferable Remember triangle of error? Imprecise local clocks (no atomic clock in your $100 receiver) Slowing of signal in the ionosphere Reflected (multipath) signals 3

4 Selective Availability Selective Availability Intentional error introduced in signal to degrade civilian signal for public safety SA turned off in 2000 Degraded accuracy to about 100m Improving GPS Accuracy Differential GPS Was most effective during SA Used ground stations at known locations that transmitted corrections More expensive, but improved accuracy from 100m to 10m (during SA) Dependant on nearby local differential transmissions Improving GPS Accuracy Visualizing GPS accuracy Random Walks Wide Area Augmentation System (WAAS) Ground stations transmit corrections to satellite Improve accuracy to 1-2m horizontal, 2-3m vertical Developed for civilian aviation instrument approach Available over United States AKA Satellite Based Augmentation System (SBAS) GPS comparison GPS Applications Too many to list in full Human Navigation Foot, Auto, Sea, Air Missile Guidance Precision Agriculture Geocaching 4

5 Personal GPS Units Many different manufacturers (Garmin, Trimble, Magellan) quite common Cost >$100 Applications for auto, boats, personal navigation Include a small screen for map display Many, many base maps available Interact with computer with cable Personal GPS Features Record Tracks Enter/Record Waypoints, & choose symbols Enter/Record Routes, intended paths to follow Virtual Compass Able to set to many different coordinate systems and map datums. Be aware of what yours is set to! Time Synchronization Vertical Profiles Sun/Moon data Fishing & Hunting data Nautical Charts Maps used to navigate the seas are called charts. Nautical Charts Unlike the land, sea charts must be updated very frequently, as depths, shorelines, objects change. Almost always use Mercator Projection because they allow for easier navigation by compass (Rhumb Lines or loxodromes) Most complete set of nautical charts in the world are the British Admiralty Charts. Santa Barbara Harbor Area SB Harbor Area 5

6 Chart Legends Differences Between Charts and Maps Usually nautical units instead of statute or metric 1 Nautical Mile = feet = miles = 1 of latitude Depths are usually in fathoms = 6 feet Blue is only used for shallow water Datum is usually mean lower low tide Soundings are point depths (spot heights), sometimes connected with isobaths, or lines of equal depth Unique symbology Notice to Mariners The US Coast Guard publishes updates to charts in text format called Notice to Mariners. Georgetown Area in Washington, DC along the Potomac (soundings in ft) Midway Islands Declination Diagram 6

7 Chart Symbology Published in Chart No. 1 Extensive symbol development Ease of translation varies Note use of hue, texture, shape Aeronautical Charts Emphasize topographical data, radio aids to navigation, airport information Features useful for visual identification from the air More pronounced use of color Aeronautical Chart Electronic Nautical Charts (ENCs) More vessels are switching to electronic charts as primary means of navigation Strengths Easily updated Cheap to distribute (free to download!) Easy to change units Automatic position and track plotting (with GPS) Weaknesses Screen size limitations Cluttered symbols Raster/Vector Comparison Raster & Vector Format Raster a digital format for images (and other data) that is described by a rectangular grid with an RGB color value Quality Resolution (number of pixels) Color Depth Does not scale (zoom) well 7

8 Raster & Vector Format Raster/Vector Comparison Vector Uses geometric structures (points, lines, curves, polygons) to define an image Allows for unlimited zooming/scaling (but doesn t necessarily retain accuracy!) Rendered to raster image as a final step Your GPS display is in vector format Move to Vector Format in ENCs Initial electronic charts were scanned copies of paper charts (raster format) Dependent on resolution of scan High resolution = high resource requirement for raster images 1 st US Navy surface warship using ENCs as primary navigation set sail May 20, 2005 Assisted Navigation Digital / Electronic Maps combined with GPS open new frontiers in map use Wayfinding Choosing a path in the built environment Can involve signage, non-traditional maps, graphic communication Wayfinding is a key element in development of spatial knowledge Route Knowledge Paths, nodes, landmarks Survey Knowledge More complete knowledge of an area Assisted Navigation Two broad types of navigation assistants to create dynamic maps Personal Guidance Systems Designed to be used by individuals May be handheld, wearable May be visual-based or not Controlled by keys, voice, gestures Vehicular Navigation Systems Aircraft, Boats, Automobiles Special issues of Situational Awareness & other important Attentional Demands Location-based Services GPS enabled phones, PDAs Find locations Your position Nearby restaurants, etc. Get directions Limitations with screen-size Head-Down Display 8

9 Wearable Computers Full-power PC attached to the body Heads Up Display A mounted eyepiece that lets you see geographic information while you move around Multi-modal interaction many methods of interaction are possible Electronic Navigation Aid Advantages Ego-centric maps Centering the map on your own position automatically Electronic Navigation Aid Advantages Use of Forward-Up convention, that minimizes cognitive load Perspective View Depth rotation Easy map storage and selection Electronic Navigation Aid Advantages Multi-modal interaction Voice, Keyboards, Mice, Eye-tracking, Gesture Recognition Standard GPS-type capabilities Waypoint, track, route recording Ability to match datums, change coordinate systems Electronic Navigation Aid Problems Many interface issues to iron out Screen size is small Voice recognition still needs work Windows Icons Menus Pointers (WIMP) Interface doesn t translate well to mobile devices May prevent development of environmental spatial knowledge Think of your knowledge when you drive vs. when you re a passenger Some people are far too trusting _Trusts_the_GPS_Too_Much.html?autoplay=true Current Capabilities Take into account User s position Construction, traffic, and other obstacles Automatic generation of routes that prioritize or consider Shortest distance Least Time Avoiding Freeways Intermediate waypoints 9