GEO101: Physical Geography

Lecture 03: Monday, January 21, 2009

Topics
1. Earth’s Magnetic Field and Compass
2. Determining Locations: GPS Basics
3. Types of Maps and Their Projection Principles
4. Remote Sensing
5. Geographic Informational Systems (GIS)
6. Quiz Question Format

Earth’s Magnetic Field and Compass
• Before GPS, people navigate using the compass;
• Compasses are made according to the Earth's magnetic field;
• The Earth's magnetic field is simulated using the "dipole" model;
• Different generations of compasses have been produced and we are still using them;
• Remember to adjust your brunton when you arrive in a new place far away from your hometown;

Determining Locations: GPS Basics
• Global positioning System (GPS) – uses radio signals transmitted from a uniform network of satellites to calculate longitude and latitude;
• It needs at least four satellites to determine the location; More satellites can obtain a better precision;
• Topographic maps can be input into the GPS, and mapping in the field;
• Have a look at the following website for more information about GPS and Map Projection;

Types of Maps and Their Projection Principles
• Essential elements of a map: Title, Date, Legend, Scale, and Direction;
• Understand the meaning of large vs. small scales of maps. Does a 1:24,000 map have a larger scale than a 1:100,000 map?
• Understand the important properties of the globe (parallels, meridians, and their relationship across the globe). What would be the advantages and disadvantages to use maps printed in a globe?
•Understand the Mercator projection (Cylindrical projection): what's advantage and disadvantage of Mercator maps?
• Understand the Gnomonic projection (Planar projection): what's advantage and disadvantage of Gnomonic maps? • If you are traveling in the ocean and you want to determine the direction you are heading, what type of map would be most helpful? If you want to determine the shortest route for the airline flying from New York to New Delhi (India), what type of map would be more useful?
• What types of map you would use is dependent on the purposes. Because in any project, the stand line or standard points are the only places where all globe properties are preserved, standard line/point should be chosen to be closest to the region of interest so that greatest accuracy is preserved there. Give an example for this (hints: look at the global maps, sometimes you see North America is put in the center of the map, but in some other maps you see North America is in the western side of the map).

Remote Sensing
• What are "active" and "passive" remote sensing? Give an examples for each of them;
• What are you viewing when you observe a weather image on TV or in the newspaper? Explain.
    Understand the following paragraphs from your textbook:
   "Our eyes and cameras are familiar means of obtaining remote-sensing information about a distant subject without having physical contact. Remote sensors on satellites and other craft sense a broader range of wavelengths than can our eyes. They can be designed to 'see' wavelengths shorter than visible light (ultraviolet) and wavelengths longer than visible light (infrared and microwave radar)."
   "Active systems direct a beam of energy at a surface and analyze the energy that is reflected back. An example is radar (radio detection and ranging). Passive remote-sensing systems record energy radiated from a surface, particularly visible light and infrared."
   "A new generation of the Geostationary Operational Environmental Satellite, known as GOES, became operational in late 1994 providing frequent infrared and visible images--the ones you see on television weather reports. GOES-10, new in 1998, is positioned above 135 degree W longitude to monitor the West Coast and the eastern Pacific Ocean. GOES-8 is positioned above 75 degree W longitude to monitor central and eastern North America and the western Atlantic. The television and newspaper weather images we see are from these platforms. GOES-11 and GOES-12, launched in 2000 and 2001 respectively, are being stored in orbit to replace older satellites as needed. Note these are images; they are not photographs, as many broadcasters and newspaper weather services mistakenly call them."

Geographic Informational Systems (GIS)
• Understand the layer structure of GIS;
• Think about the following questions: If you were in charge of planning for development of a large tract of land, how would GIS methodologies assist you? How might planning and zoning be affected if a portion of the tract in the GIS is a floodplain or prime agricultural land?

Quiz question format
• Have a look at the quiz questions in the slides. The future quizzes will have the similar format (but will not include the picture for each question), but the contents will be different.