Through a gross navigational error, the Love Boat steams into the Strait of Hormuz.

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

Geography 12: Maps and Mapping Lecture 10: Navigation III: Marine Navigation and Electronic Aids to Navigation

Review What is a back-azimuth? What is the angular difference between true north and magnetic north called? What is the problem with using dead reckoning over long distances? What does GPS stand for? Does GPS use triangulation or trilateration for finding positions?

Review What s the difference between heading and course? What do GPS and the Harrison s Chronometer have in common? What are the two methods we discussed for improving the accuracy of a GPS signal?

Lecture Outline Nautical Charts Traditional Aeronautical Charts Loran Electronic Nautical Charts Raster & Vector Assisted Navigation Wayfinding Location Based Services Personal Guidance Systems Advantages & Disadvantages

Announcements Final lab assignment issued today, due Tue, July 29 in lecture Lab next week will focus on How to lie with maps and guided research on the final lab Read chapters 1-5, 7, 8, 10. This is about 130 pages.

Paper topic: ANWAR

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

Chart Legends

Differences Between Charts and Maps Usually nautical units instead of statute or metric 1 Nautical Mile = 6076.12 feet = 1.151 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, not world datum 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

Chart Symbology Published in Chart No. 1 Extensive symbol development Ease of translation varies Note use of hue, texture, shape

Aeronautical Charts Based on Lambert Conformal Conic projection (Great Circle route approx.) Emphasize topographical data, radio aids to navigation, airport information Features useful for visual identification from the air More pronounced use of color

Aeronautical Chart

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

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 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

Raster & Vector Format 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

Raster/Vector Comparison

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

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

Golledge/Loomis Personal Guidance System (PGS) for the Blind Uses Differential GPS and Digital Compass Primary Interaction is through sound (spoken directions and responses)

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 http://tubearoo.com/articles/91916/the_office_michael _Trusts_the_GPS_Too_Much.html?autoplay=true

A bit on route selection

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

Problems Typically inflexible weighting of criteria Quickest OR Shortest OR by Road Preference (Microsoft Streets and Trips) Avoid freeways or not (Google Maps) When flexibility is present, it is often presented in a confusing way

Expressing Preferences (1) Microsoft Streets and Trips interface for expressing preference for road types How are these four rating criteria related?

Expressing Preferences (2) Google Maps Default Route (16.3 mi, 23 min) These two routes take entirely different paths Quite similar with respect to distance, time, overall trend, and highway use Quite different with respect to time in city, risk of traffic congestion, and initial route segment Avoid Highways (17.4 mi, 27 min)

Overall Problem Current navigation systems oversimplify the criteria of route selection so that they can provide a single best route based on expressed user preferences Better solution Use GPS data to analyze travel patterns which can be classified and combined with expressed user preferences Provide more input options based on an intelligent classification of travel strategies Find nearly equivalent best routes and present these to the user. Use responses to further calibrate user strategic travel profile

Preferences and Heuristics as Strategies Preferences (interrelated criteria) Shortest distance Least time Fewest turns Straightest path Avoid freeways Aesthetic appeal Avoid left turns Safety Least complex Heuristics (approximate solutions) Reduce cognitive load by delaying choice (Christenfeld, 1995) Choose initially long straight segments (ISS) (Bailenson et. al, 2000/2002) Choose path with least angular deviation from target (Hochmair and Frank, 2000) Move to regions containing target as soon as possible (Wiener and Mallot, 2003)

Initial Straight Segment Strategy

Initial Segment Analysis

Route Asymmetry

Next time Intro to cartography, please read Monmonier 1-2.