Transcript Slide 1
Mapping Systems Worldmap by Abraham Ortelius- 1670 Worldmap by Rumold Mercator- 1687 Take two minutes to brainstorm the similarities and differences between these maps. http://geology.isu.edu/geostac/Field_Exercise/topomaps/images/projections.jpg Map Projections A map projection is any method of representing the surface of a sphere or other shape on a plane. Adapted from: http://www.fs.fed.us/database/gps/aboutgps/documents/usi_maps.ppt#572,1,Using Maps with GPS The Problem: Projecting a Sphere Onto a Plane Three-dimensional sphere to two-dimensional flat map. Examples of Several Projections Depending on the projection, a certain amount of distortion occurs when portraying the earth on paper. South America in selected projections at identical scale. Which projection is best? Which is right? The short answer is none, at least not all the time. Even if a single projection is used, just switching the aspect can also radically reshape the continents. http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html Projections and Datums Meade Ranch (Clarke 1866) Determining Latitude & Longitude Latitude & Longitude Determining Latitude 80° N 30° N 80° 30° 30° 30° S . Equator- 0° Latitude Latitude is comprised of parallels, which are equally spaced circles around the earth paralleling the Equator. Parallels are designated by their angle north or south of the Equator (10º, 20º, etc) . The Equator is 0º latitude, and the north and south poles are at 90º angles from the Equator. The linear distance between parallel (latitude) lines never changes, regardless of their position on the earth. Parallels of Latitude 20º N 10º N 0º N 10º S 10º 690 miles 10º 690 miles 10º 690 miles Or… the distance on the ground between every 1° of latitude is just over 69 miles! Determining Longitude Prime Meridian- 0° 30° 30° W . Equator- 0° 110° 30° 30° E Longitude Longitude is comprised of meridians that form one-half of a circle, or plane. Meridians are designated by their angle west or east of the prime meridian. The prime meridian is designated 0º and extends from the north pole to the south pole through Greenwich, England. Meridians are angled, and do not parallel each other. The linear distance between one degree of longitude at the Equator is approximately 69 statute miles. The linear distance between one degree of longitude at the arctic circle is only about 26 statute miles. Meridians of Longitude To North Pole 10º 240 mi 10º 460 miles 10º 690 miles Equator To South Pole 120º W 110º W Example of a USGS Map Legend • • • • • • • • • Mapped, edited, and published by the Geological Survey Control by USGS USC&GS Topography from aerial photographs by multiplex methods and by plane-table surveys 1953. Aerial photographs taken 1951 Polyconic projection. 1927 North American Datum 10,000 foot grid based on Idaho coordinate system, west zone 1000-meter Universal Transverse Mercator grid ticks, 1000-meter Universal Transverse Mercator grid ticks, zone 11, shown in blue To place on the predicted North American Datum 1983 move the projection 0 28’ 18 1/20 0 lines 15 meters north and 77 meters east as shown by dashed corner ticks 8 MILS 329 MILS UTM GRID AND 1971 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET Latitude & Longitude Prime Meridian (Longitude) 0º 0º Equator (Latitude) Point of Origin Latitude & Longitude N Prime Meridian 30º 20º W 30º 20º 10º + 10º 10º 20º 30º E 10º 20º Equator 30º S 0º, 0º The Units to Measure Angles Degrees: There are 360 degrees in a Circle. Degrees are abbreviated with the symbol: ° Minutes: There are 60 Minutes in 1 Degree Minutes are abbreviated with the symbol: ‘ Seconds: There are 60 Seconds in 1 Minute Seconds are abbreviated with the symbol: “ Example: DDD° MM' SS.S" 32° 18' 23.1" N 122° 36' 52.5" W Time Zones Greenwich Mean Time UTM Coordinates Universal Transverse Mercator Is a rectangular (planar) coordinate system based on the latitude and longitude (geographic) coordinate system. The earth is divided into 60 UTM zones. Sixty zones allows the earth to be projected onto maps with minimal distortion. UTM uses “false” values (easting and northing) to express coordinates. Coordinates are expressed in meters. UTM Coordinates UTM Zone Number Easting Coordinate 11T 0541450 4789650 UTM Latitude Band Letter Northing Coordinate UTM Grid Overlay 60 Zones, and 20 Latitude Bands 1 Latitude Bands 84º N 80º S X W V U T S R Q P N M L K J H G F E D C Zones 21 60 21 T Equator See If You Can Tell In Which Quarter These Lon/Lats Are Located A C • • B • D • • • 1. 41°N, 21°E 2. 37°N, 76°W 3. 72°S, 141°W 4. 7°S, 23°W 5. 15°N, 29°E 6. 34°S, 151°E • 1. B • 2. A • 3. C • 4. C • 5. B • 6. D