Key Terms for Maps 1 east parallels 15 International Dateline previous 24 longitude smaller 60 meridians south angular distance midnight southeast (SE) clockwise next day differences within the same north country Summary: This chapter introduces you to the tools that aid geographers in their study of the physical aspects of the Earth. These are maps, aerial photographs, remotely sensed data, and geographic information systems. Map scales, features, the distorting of the Earth by flat maps, and types of map projections are discussed in the chapter. Also, the uses of satellites and computers as tools for the geographer to gather information is given. It is important that you understand how to interpret map scales (graphic and fractional) and how that maps are equivalent or conformal in nature. Since it is impossible to project a three-dimensional sphere onto a flat surface with complete accuracy, the resulting distortion may serve to perpetuate inaccurate images of Earth's surface in the minds of the public. In Portraying the Earth, the authors illustrate the many methods cartographers use to transform the three-dimensional sphere into an understandable two- dimensional document. (Image: University of Wisconsin, 2007. http://www.geography.wisc.edu/maplib/images/robinsonproj.gif cited 19 June 2007 Objectives: To Successfully be Able to: 1. use the earth's reference grid: latitude, longitude, meridians, parallels 2. use mapping basics: scale, direction, and map symbolization 3. calculate how time is determined for any portion of the globe. Misconceptions: 1. Most of Africa is south of the equator 2. Traveling south from Michigan will take you to South America 3. Minneapolis, MN is further north than Venice, Italy OBJECTIVE 1: use the earth's reference grid: latitude, longitude, meridians, parallels One method for locating points on the globe is through a coordinate grid system known as latitude and longitude. Latitude, is the north or south of the equator and ranges from 0° at the equator to 90° north or south of the equator. Latitude is measured by east west lines called ______________________. is the angular distance east or west of the prime meridian, a north south line bisecting Greenwich, England. Longitude is measured by north south line called ________________________. Locate the prime meridian and equator on your globe. What line is 180° east or west of the prime meridian? Longitude ranges from 0° at the prime meridian to 180 degrees east or west of the prime meridian. By convention, latitude precedes longitude. Cardinal direction, N, S, E, W, must accompany any citation of latitude and longitude. The examples below are valid formats for locating points on the globe using latitude and longitude. 23° N, 38° E 84° N, 77° W 13° S, 15° E 70° S, 179° E To locate points with greater accuracy, any degree of latitude or longitude can be subdivided into minutes (represented by the ' symbol). Furthermore, any minute of latitude or longitude can be subdivided into 60 seconds. The coordinates 84° 34' 39" N, 155° 43' 34" W specifies an earth location with much greater accuracy than simply using degrees. Note that degrees or seconds of latitude cannot exceed 59 unless converted to the decimal system. For example 84° 30' E converts to 84.5 °E in the decimal system. Using an atlas, discover the latitude and longitude of Mt. Pleasant, Michigan. OBJECTIVE 2: use mapping basics: scale, direction, and map symbolization. Scale: 1) representative fraction: As you page through the maps you will be using you may have noticed that you see fractions such as 1:24,000, 1:62,500, 1:125,000, and 1:250,000 in the legend. This is the scale which shows the relation between the size of the feature on the map and the size of the feature in the real world. The larger the scale the the smaller the denominator of the representative fraction; the area covered is smaller and the greater the detail of the features represented. Rank order (1,2,3) the following maps according to scale, area,and detail covered: map of Mt. Pleasant, and map of the state, and a map of the world. Area Detail Scale Mount Pleasant Map of the State Map of the World 2) graphic scale: are also found in legends and are easy to use. Here, a segmented line or bar actually displays the ground distance on the map. (Image: Extranet, 2007, http://www.extranet.vdot.state.va.us/loc des/caddman/graphics/sbar50.gif accessed 25 June 2007) 3) verbal scale: represents the relationship between map and real world distance (one inch on the map equals one mile on the ground; 1" = 1 mile). 1:24,000--one inch equals less than one half mile 1:62,500--one inch equals approximately one mile 1:125,000--one inch equals approximately two miles 1:250,000--one inch equals approximately four miles Direction: the top, bottom, right, and left portions of the map are usually represented as north, south, east, and west respectively. 1) cardinal direction: one of four traditional directions, ________________________________________and west found on a compass. Intermediate directions (image to lower left) include northeast (NE), __________ and southwest (SW), and northwest (NW) (Image: Barnabybear, 2007. http://www.barnabybear.net/resources/compass.jpg accessed 25 June 2007) 2) azimuth (image above) : a horizontal angular distance made ________________________ through 360° usually beginning from north, which acts at the 0° reference direction. (Image: City of Ardmore, G.I.S. Dept, 2004, http://www.gis.ci.ardmore.ok.us/Images/Azimuth.GIF accessed 25 June 2007) OBJECTIVE 3: calculate how time is determined for any portion of the globe. There are time zones that exist for the world. Each time zone is ° wide. This is based on the fact that the earth rotates through 360° of longitude in a 24 hour period. While it is true that time zone boundaries closely follow meridians (lines of longitude) over the oceans, these lines are highly irregular over the land. The occurs because governments don't want . Reset your watch hour every time you cross a time zone. When moving from east to west, Detroit to Seattle, for example, time becomes earlier. If moving from Seattle to Detroit time becomes later. To understand this concept get a globe look at France, place your hands around the earth's equator and slowly move the globe so that the Arctic Circle is rotating counterclockwise. This mimics the earth's eastward rotation (counterclockwise when viewed from the north pole). Imagine your eyes are the sun. Imagine that when you are directly looking at France and it is noon; you could just barely see New York, this would be sunrise for people living in New York. Rotate the earth more in the counterclockwise direction so that New York comes into view and is when directly in front of your eyes; now New York is experiencing noon. You can now barely see France; Paris is experiencing sunset. Hawaii is just starting to appear. Hawaii is experiencing sunrise. The date can change in two ways: 1) when the time passes 2) when crossing the . (IDL) This line is 180° meridian and runs down the middle of the Pacific Ocean. When crossing the IDL from Japan to Los Angeles, west to east, the date changes to the day. Why? We can't time travel into the future. When traveling east time gets later every time a time zone is passed. To prevent "time travel" into the future, the date will change. When crossing the IDL from Los Angeles to Japan, the date changes to the day. When traveling west time gets earlier every time a time zone is passed. We can't time travel back in time. To prevent "time travel" into the past, the date will change. The IDL runs down the middle of the time zone. When crossing the IDL only the date changes, not the hour. The hour will change only when crossing the boundary of the next time zone.
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