1 Representations of the Earth Maps, GIS and Remote Sensing

© Vicki Drake2 The first Lines of Parallel and Meridians

© Vicki Drake3 LATITUDE AND LONGITUDE Lines of Parallel equate to Latitude. Latitude is measured from the equator to the poles (0 0 – 90 0 ) Lines of Meridians equate to Longitude. Longitude is measured from the Prime Meridian (0 0 ) to International Date Line (180 0 E/W)

© Vicki Drake4 Coordinate Systems –Latitude and Longitude

© Vicki Drake5 MEASURING LATITUDE The equator is a Great Circle: dividing the earth into two equal halves The equator is a Great Circle: dividing the earth into two equal halves Lines of latitude are parallel and evenly spaced: a degree of latitude represents a constant distance on the ground. Lines of latitude are parallel and evenly spaced: a degree of latitude represents a constant distance on the ground. – Approximately 69 miles (111 kilometers) These lines of parallels are measured in angular degrees (°). These lines of parallels are measured in angular degrees (°). – There are 90 angular degrees of latitude from the equator to each of the poles. – The equator has an assigned value of 0°. – Measurements of latitude are also defined as being either north or south of equator to distinguish the hemisphere of their location

© Vicki Drake6 MEASURING LONGITUDE All lines of longitude can be “Great Circles” All lines of longitude can be “Great Circles” Lines of longitude or meridians are non-parallel circular arcs that meet at the poles. Lines of longitude or meridians are non-parallel circular arcs that meet at the poles. – At the equator, a degree of longitude measures approximately 69 miles (111 kilometers) – At 40 0 N or S, a degree of longitude measures approximately 53 miles (85 kilometers) – At the poles, a degree of longitude measures 0 miles or kilometers – all meridians converge to a single ‘point’ at the north or south pole There are 180° of longitude either side of a starting meridian which is known the Prime Meridian. There are 180° of longitude either side of a starting meridian which is known the Prime Meridian. – The Prime Meridian has a designated value of 0°. – The Prime Meridian starts at Royal Observatory, Greenwich, London, England Measurements of longitude are also defined as being either west or east of the Prime Meridian. Measurements of longitude are also defined as being either west or east of the Prime Meridian. The maximum value that a meridian of longitude can have is 180° which is the distance halfway around a circle. The maximum value that a meridian of longitude can have is 180° which is the distance halfway around a circle. – This meridian is called the International Date Line. – Designations of west and east are used to distinguish where a location is found relative to the Prime Meridian. For example, all of the locations in North America have a longitude that is designated west. For example, all of the locations in North America have a longitude that is designated west.

© Vicki Drake7 Projections--Going from 3D to Flat Maps

© Vicki Drake8 Projections—From a Sphere to Flat Maps ÔProjections are created by transferring points on the earth onto a flat surface. You can think of this as having a light in the middle of the earth, shining through the earth’s surface, onto the projection surface. There are three basic methods for doing this: Ô Cylindrical--projection surface wrapped around the Earth; point of contact is equator ÔConformal projection (‘preserves’ shape of continents at equator only) Ô Planar--projection surface is a ‘flat’ surface against the Earth at a particular latitude or longitude ÔNeither Conformal or Equal Area Ô Does not ‘preserve’ shape of continents nor provide measure for equal area Ô Conic–- projection surface is a cone is placed on or through the surface of the Earth ÔWhere the projection surface touches the Earth is the “Standard Line.” ÔCan be either Conformal or Equal Area

© Vicki Drake9 Trouble with Projections ÔDistortion--It is impossible to flatten a round object without distortion. ÔProjections try to preserve one or more of the following properties: Ô Area--sometimes referred to as equal area (for small areas) ÔProjections that preserve ‘area’ are referred to as “Equal Area” projections Ô Shape--usually referred to as “conformality”, again for small sections ÔProjections that preserve “shape” are referred to as “Conformal” projections Ô Direction--or “azimuthality” - cardinal directions (N,S,E,W) Ô Distance – a difference in distance between two points on the Earth and same two points represented on map

© Vicki Drake10 PROJECTION CHALLENGES Conformality Conformality –When the scale of a map at any point on the map is the same in any direction, the projection is conformal. Meridians (lines of longitude) and parallels (lines of latitude) intersect at right angles. Meridians (lines of longitude) and parallels (lines of latitude) intersect at right angles. Shape is preserved locally on conformal maps. Shape is preserved locally on conformal maps. Distance Distance –A map is equidistant when it accurately portrays distances from the center of the projection to any other place on the map. Direction Direction –A map preserves direction when azimuths (angles from a point on a line to another point) are portrayed correctly in all directions. Area Area –When a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the Earth that they represent, the map is an equal-area map. Scale Scale –Scale is the relationship between a distance portrayed on a map and the same distance on the Earth. CONFORMAL VS EQUAL AREA: Projections can be either conformal or equal area – but not both! CONFORMAL VS EQUAL AREA: Projections can be either conformal or equal area – but not both!

© Vicki Drake11 Projections--Cylindrical Projection Point of contact at equator

© Vicki Drake12 Projections--”Developing” a Cylindrical Projection

© Vicki Drake13 Cylindrical Projection: A Conformal Projection Note increasing distance between lines of latitude….why?

© Vicki Drake14 Why Mercator? NAVIGATION!! In a Mercator projection, the lines of longitude are straight vertical lines equi-distance apart at all latitudes, and horizontal distances are stretched above and below the equator. In a Mercator projection, the lines of longitude are straight vertical lines equi-distance apart at all latitudes, and horizontal distances are stretched above and below the equator. This stretching is exaggerated near the poles This stretching is exaggerated near the poles –The Mercator projection mathematically stretches vertical distances by the same proportion as the horizontal distances so that shape and direction are preserved –Shape is preserved….what happens to the measurement of area? Mercator’s projection preserves exactly what sailors in the 16 th century needed -- shapes and directions; they were very willing to accept the size distortion. Mercator’s projection preserves exactly what sailors in the 16 th century needed -- shapes and directions; they were very willing to accept the size distortion. Any straight line drawn between two points on a Mercator Projection represents a “rhumb line” – true compass direction Any straight line drawn between two points on a Mercator Projection represents a “rhumb line” – true compass direction

© Vicki Drake15 Rhumb Line – True Compass Heading: Mercator Projection Mercator Projection was the navigation map for sailing ships: good direction but longest route

© Vicki Drake16 MERCATOR PROJECTION The normal aspect of the Mercator projection showing the great circle between Miami and Tokyo The normal aspect of the Mercator projection showing the great circle between Miami and Tokyo –Great Circles are the shortest distance between two points on a globe Shortest distance, but not true compass headings

© Vicki Drake17 Projections--Polar Planar Projection

© Vicki Drake18 Polar Planar Projection Projection centered on North Pole

© Vicki Drake19 Planar Projection: Gnomonic Gnomonic projections can be either “Conformal” or “Equal Area”, but not both

© Vicki Drake20 Gnomonic Projection

© Vicki Drake21 NAVIGATION: GNOMONIC Any straight line drawn on a gnomonic projection is an Arc of a Great Circle Route – shortest distance between two points on a globe Any straight line drawn on a gnomonic projection is an Arc of a Great Circle Route – shortest distance between two points on a globe –Great circles are represented by straight lines, making it very useful in plotting great circle routes between arbitrary destinations Gnomonic Maps are the navigational maps for “air” age Gnomonic Maps are the navigational maps for “air” age Straight line between two points on map is shortest distance

© Vicki Drake22 Projections--Conic Projection

© Vicki Drake23 Conic Conformal Projection

© Vicki Drake24 CONIC PROJECTIONS A better choice for mapping regions such as the United States is a conic projection, which projects shapes from the Earth’s sphere onto a cone. A better choice for mapping regions such as the United States is a conic projection, which projects shapes from the Earth’s sphere onto a cone. Locations near the line where the cone is tangent to the Earth will be relatively free of distortion Locations near the line where the cone is tangent to the Earth will be relatively free of distortion

© Vicki Drake25 PROBLEMS WITH CONIC PROJECTIONS Projection Distortion-- shown with a conic projection cutting through the earth’s surface at 2 parallels

© Vicki Drake26 PROJECTION WOES!

© Vicki Drake27

© Vicki Drake28 MAP SCALE Map Scale is the ratio of the distance between two points on the Earth’s surface and the distances between corresponding points on a map Map Scale is the ratio of the distance between two points on the Earth’s surface and the distances between corresponding points on a map There are several types of map scales: There are several types of map scales: –Verbal Scale: 1 inch = 1 mile –Bar Scale: a graph depicting distances –Representative Fraction: One unit of measured distance on a map equal some units of measured distance in the real world One unit of measured distance on a map equal some units of measured distance in the real world

© Vicki Drake29 REPRESENTATIVE FRACTION Representative Fraction (RF) is the ratio between measured distances on a map and measured distances on the Earth’s surface. Representative Fraction (RF) is the ratio between measured distances on a map and measured distances on the Earth’s surface. RF is a unitless measure – however, both sides of the ratio must be identical units RF is a unitless measure – however, both sides of the ratio must be identical units A RF scale expressed as a ratio of 1:25,000 means that one unit of distance measured on the map represents 25,000 identical units of distance on the ground (‘in the real world’). A RF scale expressed as a ratio of 1:25,000 means that one unit of distance measured on the map represents 25,000 identical units of distance on the ground (‘in the real world’). –1 inch measured on a map represents 25,000 inches on the Earth’s Surface or… –1 cm measured on a map represents 25,000 centimeters on the Earth’s surface.

© Vicki Drake30 LARGE-SCALE VS SMALL-SCALE Large-Scale Maps show very small portions of the real world, but with great detail. Large-Scale Maps show very small portions of the real world, but with great detail. –Large-Scale maps have small denominators i.e., 1:12,000 or 1:10,000 –Topographic maps are examples of large-scale maps Small-Scale maps show very large portions of the real world, but with minimal detail Small-Scale maps show very large portions of the real world, but with minimal detail –Small-scale maps have large denominators, i.e., 1:100,000 or 1:1,000,000 –Wall maps are examples of small-scale maps

© Vicki Drake31 LARGE SCALE VS. SMALL SCALE

© Vicki Drake32 Very Early Maps! Town Plan from Catal Hyük, Anatolia (6200 B.C.) Reconstruction of Drawing

© Vicki Drake33 Early Maps Clay tablets from Ga- Sur Clay tablets from Ga- Sur 2500 B.C B.C. Interpretation of drawing

© Vicki Drake34 Early World Maps The world according to Herodotus 450 BC The world according to Herodotus 450 BC

© Vicki Drake35 Early World Map Reconstruction of world map according to Dicaearchus (300 B.C.) Reconstruction of world map according to Dicaearchus (300 B.C.)

© Vicki Drake36 Babylonian Clay Map and Interpretation – 600AD

© Vicki Drake37 Topographic Maps

© Vicki Drake38 3-D Topographic Maps

© Vicki Drake39 Temperature Maps

© Vicki Drake40 Ethnicity Maps

© Vicki Drake41 Sea Floor Maps

© Vicki Drake42 Precipitation Maps

© Vicki Drake43 Population Maps

© Vicki Drake44 COMPUTER MAPPING: GIS GIS, Geographic Information Systems, are a way to visualize, manipulate, analyze and display spatial and non-spatial data – –Spatial data is geo-referenced – –Non-spatial data is descriptive A spatial database (“geodatabase”) is used

© Vicki Drake45 GIS is an Integrating Technology

© Vicki Drake46 HOW DO GIS USE DATABASES? Geodatabases provide geo-referenced and descriptive data for analysis Geodatabases provide geo-referenced and descriptive data for analysis

© Vicki Drake47

© Vicki Drake48 Cities use GIS to locate vulnerable pipelines

© Vicki Drake49 Parcels in 100-year Flood Zone

© Vicki Drake50 Income Maps – Census tracts

© Vicki Drake51 Earthquake Maps - Locations

© Vicki Drake52 Earthquake Maps – Faults

© Vicki Drake53 Southern California Earthquakes, Creating Density Maps

© Vicki Drake54 3-Dimensional Symbolization of Data (using 3-D Analyst)

© Vicki Drake55 Remote Sensing and Maps

© Vicki Drake56 Remote Sensing Platforms

© Vicki Drake57 Typical Remote Sensing Platforms used today Typical Remote Sensing Platforms used today

© Vicki Drake58

© Vicki Drake59 Remote Sensing uses Energy

© Vicki Drake60 Spectral Signatures All objects (natural or synthetic) reflect and emit electromagnetic radiation over a range of wavelengths characteristic of the object. Distinctive reflectance and emittance properties are the spectral signatures of object Remote sensing depends upon operation in wavelength regions of spectrum where these spectral signatures occur for identification purposes.

© Vicki Drake61 GrasslandNeedleleaf Forest Water Broadleaf shrubs

© Vicki Drake62 Space-based Remote Sensing When the sun’s energy passes through the atmosphere, three reactions can occur: When the sun’s energy passes through the atmosphere, three reactions can occur: – Transmission – Reflection – Scattering – Absorption

© Vicki Drake63 Spatial Resolution – by pixel MODIS: 250meters x 250meters Landsat: 30meters x 30meters IKONOS: 1meter x 1meter

© Vicki Drake64 Sample Landsat TM image along Missouri River