Geog 170 Final Exam Study Guide PDF

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Geography 170 Our Digital Global: GIScience & Technology Final Exam Review Questions 1. Introduction to Geospatial Technology ○ What is geospatial technology? ■ Describes the use of a number of different high- tech systems & tools to acquire, analyze, store, manage, or visualize various types of location-based data ■ Includes information about or attached with space & location ■ Can be applied in many ways: federal, state, and local government, forestry, law enforcement, public health, biology, environment, and transportation ○ What are three major geospatial technologies? ■ 1) Geographic Information System (GIS): a computer based geospatial tech. For storage, analysis, and management of location-based data ■ 2) Remote Sensing (RS): a technology that is used to acquire imagery of the earth’s surface through the use of satellites or aircraft. ■ 3) Global Positioning System (GPS): a technology that acquires realtime location information from a series of satellites in Earth’s orbit. ○ What is google Earth? 3D Virtual Globe ■ A widespread geospatial technology application ■ A virtual globe, map, and geographical information program. ■ Maps the Earth the superimposition of images obtained from satellite imagery, aerial photography and geographic information system onto a 3D globe ○ Self-Assessment 1: ■ 1) Which of the following is NOT a form of geospatial technology? JPEG: a image format instead of geospatial technology ■ 2) Acquiring real-time location information from a series of satellites in Earth's orbit is the goal of _______. GPS. ■ 3) Match the functionality to the corresponding geo-spatial technology. GIS → Manage and analyze. GPS → acquire

geospatial coordinates of

a locat location. ion.

■ 4) Geography is the study of ______________. spatial characteristics of Earth, and the relationships between people and these spatial characteristics. ■ 5) Geospatial technology is often used for environmental monitoring but rarely used for people-centric activities like law enforcement or health and human services. False. ■ 6) Google Earth presents a 3D representation of Earth. True

2. Geographic Information and Representation ○ What is geographic information? ■ Information that has location (x,y) component as well as other associated attributes or characteristics ■ Time is an optional element in geographic information, but the location is essential. ■ Geographic attributes are specific statistics tied to geographic location, e.g., Population density, Tax rates, Health data (lung cancer rate), Temperature, Air pressure ○ How do you represent geospatial information? ■ Through maps: a spatial representation of the geographic information that is presented graphically ● Reference map: depict locations (ex: Road maps, Google maps, Bing Map, mapquest.com, Openstreetmap.org, USGS Topo maps) ● Thematic map: depict spatially-referenced variables of interest (ex: weather, population density, and geology maps) ● Navigational maps: depict paths and routes (nautical charts: created specifically for water navigation and aeronautical charts: designed for the air navigator filling with information important to safe flying) ● Persuasive map: present a graphical argument (ex: advertising, political, and religious maps) ○ Self- Assessment 2:

■ 1) Which of the following is NOT a form of geospatial data? The assessed value of a particular house ■ 2) All data have a spatial aspect. False ( Not all data have a geospatial aspect. One example: the ISBNs of books on the shelves in a Library do not have a geospatial aspect) ■ 3) In general, geospatial data and nonspatial data cannot be linked in useful ways. False (In fact, geospatial data and nonspatial data CAN be linked in useful ways. You will learn how to link them using GIS techniques :-) 3. Geodetics ○ What is geographic coordinate system? ■ A reference system that uses a three-dimensional spherical surface and measures of latitude and longitude to define locations on the Earth. ○ What are the units and range of geographic coordinates? ■ Unit: degrees ■ Latitude: the angular distance between the Equator and points to the north or south on the surface of the Earth, 0 degrees-90 degrees ■ Longitude: lines that pass through both poles referenced by their angular distance east or west from the Prime Meridian., 0 degrees180 degrees. Length of a degree of longitude decreases from the equator to a pole ■ Length of a degree of longitude decreases from the equator to a pole ○ What are ellipsoid, datum, and geoid? ■ Describing the Shape of the Earth: ● Ellipsoid/ spheroid: way to describe the shape of the earth, a mathematical figure approximating the shape of Earth where the major axis (the equator) is larger than the minor axis b (the N-S pole), model the Earth as a smooth surface, larger radius (bulges) at the Equator ● Geodetic datum: a way to describe the shape of the earth, a reference base that defines the size and shape of the Earth

in order to locate positions and places. can be defined using: the ellipsoid, the coordinates of a base point, or the direction north and can be horizontal or vertical ○ Horizontal datum: measure a specific position on the Earth's surface using coordinate systems such as latitude and longitude. ■ EXAMPLES: North American Datum of 1927 (NAD27), North American Datum of 1983 (NAD83), World Geodetic System 84 (WGS84) ○ Vertical datum: technically an arbitrary surface of zero elevation, allows height measurements of various points in a consistent system. more broadly, a vertical datum is the entire system of the zeroelevation surface as well as methods of determining heights relative to that surface ■ EXAMPLE: geoid ■ Geoid: ● a vertical datum and a hypothetical Earth surface that represents the mean sea level, assuming Earth's surface is completely covered by water ● Accounts for variations in gravity across earth’s surface ○ Self- Assessment 3: ■ 1) Earth is perfectly round. False. ■ 2) A reference surface or model of Earth, used for plotting locations across the globe, is called a(n): Datum. (A reference surface or model of Earth). ■ 3) Measurements made from one datum may not precisely match the measurements made from another datum. True. ■ 4) The Equator and the Prime Meridian both have a value of _____________ in geographic coordinate systems. Zero. ■ 5) Lines of latitude run in an east-to-west direction around the globe. False (Lines of latitude run in an east-to-west direction around the globe.) ■ 6) The key reference point for lines of latitude is the: Equator. ■ 7) Lines of longitude are also known as parallels. False: lines of

latitude are often called parallels. ■ 8) A degree is composed of _______ minutes, and a minute is composed of ______ seconds. 60;60 ■ 9) Negative values can be used when making measurements ______ of the Equator and/or ______ of the Prime Meridian. South; west ■ 10) When making measurements on a sphere, the distance between two points is referred to as the: Great circle distance. ■ 11) Go north 8°42  53" from 23°34  32"N. What is your latitude? In order to get the new latitude, we need to add degrees, minutes, seconds of both values: Step 1. Seconds: 32 + 53 = 85''. Since 60 seconds equal to 1 minute. So we have a total of 1 minute, 25 seconds after adding the values of seconds. Step 2. Minutes: 34 + 42 = 76. After getting additional 1 minute from previous step, we have a value of 77 minutes, equaling to 1 degree, and 17 minute. Step 3. Degrees: 23 + 8 = 31 degree, and we also need to add 1 more degree derived from the step 2, giving us a total value of 32. So the final result is: 32°17  25". Also another way to solve the problem is to convert them from DMS to decimal degrees and then add. 4. Map Projection ○ A map projection is a mathematical process of transforming a particular region of the earth's three-dimensional curved surface onto a twodimensional map. ○ What kind of distortions would occur while transforming a curved earth flat to a map? ■ Types of distortions: Area, shape, distance, or direction ○ Does distortion always occur? ■ Yes ○ What project surfaces are used for cylindrical, conical, and planar projections? ■ By projected surface type: ● Cylindrical: project information of the spherical Earth to a cylinder ● Conical: project information of the Earth to a _______

cone, a type of map projection that projects Earth onto a cone that is either tangent to the Earth at a single parallel, or secant at two parallels. ○ If we wrap a sheet of paper around the Earth in a cone shape, we would produce a conic projection. Once the projection is complete, the cone is unwrapped to form a flat surface. ○ In a conic projection (Figure 8), a cone could either be tangent to the Earth at a single parallel, or secant at two standard parallels. We refer to the parallels that touch or intersect with the Earth as standard parallels. ○ 1) Good for polar regions; the standard map of Canada uses a conic projection (Lambert Conformal Conic). ○ 2) Good for aeronautical maps because it shows latitude in the form of a circle. ● Planer: a type of map projection that projects Earth's surface onto a flat plane by placing the plane at a point on the globe. ○ A planar projection projects the Earth onto a plane by placing the plane so that it touches a point on the globe; the plane may be either tangent or secant (Figure 9). The point of contact is called the focus, which defines the type of planar projections into three classes: ○ Polar planar projection - the focus is located at one of the poles ○ Equatorial planar projection - the focus is located at any point along the equator ○ Oblique planar projection - the focus is located at neither a pole nor along the equator ○ What geometrical properties (area, shape, distance, direction) do Conformal, Equivalent, Equidistant, Azimuthal, and Compromise projections attempt to preserve or maintain?

■ Conformal: preserve shape (angles on the globe) ■ Equivalent (equal area): preserve size or area ■ Equidistant: preserve distance ■ Azimuthal or Zenithal: preserve direction ■ Compromise: not preserve any particular feature (area, shape, distance, or direction), but minimize distortion of all or a few of these ○ What are the differences between tangent and secant projections? ■ Tangent projections: Projection surface touch the globe surface along a line (a line of tangency) ■ Secant projections: have two lines of contact or tangency between the projection surface and globe surface, therefore, two standard parallels. ○ Which line(s) or points on the map have the least distortion? ■ The lines where the cone, cylinder, or plane is tangent with the globe surface or secant are the places with the least distortion ○ What is a graticule? ■ To map tropical regions, use a cylindrical projection ■ To map the middle latitudes, use a conic projection ■ To map a polar region, use an azimuthal projection 5. Coordinate Systems ○ What is a geographic coordinate system (GCS)? ■ Unprojected coordinate system ■ Use latitude & longitude to represent coordinates ○ What are commonly used projected (planar/Cartesian) coordinate system? ■ Universal Transverse Mercator coordinate system (UTM) is the most commonly used global projected coordinate system. It is used by federal governmental agencies such as the USGS. ■ State plane coordinate System(SPCS) was created in the 1930s by U.S. land surveyors as a way to define property boundaries in a way that would make them easier to measure. They are widely used by surveyors, engineers, planners, and state and local governments. They provide a common basis for assigning coordinate values to all areas of a State. ○ What is Universal Transverse Mercator (UTM) coordinate system and

State PPlane Coordinate System? ■ UTM ● Unit: meters ● Divide the world into 60 zones ○ UTM zones are numbered from 1 to 60 starting from 180° longitude at the International Date Line (Read more in Box 1) and proceeding eastward. Therefore, Zone 1 lies between the 180°W to 174°W longitude lines and is centered at 177°W; Zone 2 is between 174°W and 168°W longitude. Zone 60 covers longitude 174°E to 180°E (the International Date Line) (Figure 3). Each zone is also formatted with an "N" or "S" after the zone number, indicating whether the zone is in the North or South hemisphere. We will learn more about why this is done in the following sections. ● Projection: Transverse Mercator projection ● Two false origins are established for each zone to make sure northing (y) and easting (x) value positive ● Example: 305,900m E, 4,771,650mN, Zone 16 North ● In a UTM coordinate system, easting is the east-west xcoordinate, which is the distance from the origin. Easting varies from near zero to near 1,000,000 m. In both the northern and southern hemispheres, the center line (central meridian) of each zone has an easting value (x values) of 500,000 m to ensure that there are no negative values (Figure 5). This value, called false easting, is added to all xcoordinates so that there are no negative easting values in the zone. Since this 500,000m value is arbitrary. eastings are sometimes referred to as "false eastings". ● Example: 305,900m E, 4,771,650mN, Zone 16 North\ ■ SPCS ● Zone boundaries coincide with state and national borders ● Two false origins are established ● Projection: Projections for each State chosen to minimize distortions ● Similarly, a northing is the north-south y-coordinate in a projected coordinate system. In the northern hemisphere, a northing value of 0 m is assigned to the equator. Since no false northing value is added, a UTM northing value for a zone in the northern hemisphere is the number of meters

north of the equator. In the southern hemisphere, a false northing of 10,000,000 m is given to the equator so that all northing (y-axis) values are positive numbers. ● Predominantly east-west states (such as Texas) use Lambert conformal conic. Lambert conformal conic projection is used for states of predominantly east-west extent. For example, Colorado is a Lambert state with three zones. ● States of greater north-south extent use Transverse Mercator projections ● Example: 2, 164, 600 ft E, 392, 280 ft N, Wisconsin, south zone. ○ What unit/ projection is used in UTM coordinate system? ■ The unit of measurement is meters and it uses a Transverse Mercator projection ○ Why are false northing or easting value issued? ** 6. Map Scale ○ What is map scale? ■ Map scale expresses the relationship between distances on the map and their corresponding ground distances. Using map scale, measurements made on a map can be converted to ground units. In other words, we are able to know the real distance between two places by measuring their distance on the map using simple tools like a ruler. ■ Methods to represent scale: ● Representative fraction (RF): 1:50,000 ● Verbal scale: 1 inch to 2 miles ● Scale bar (graphic scale) ○ How do you calculate ground distance based on map scale and map distance? ■ 1) Measure the distance between any two points on the map. This distance is the map distance (MD). ■ 2) Determine the horizontal distance between these same two points on the ground. This distance is the ground distance (GD). ■ 3) Use the representative fraction (RF) formula, and remember that RF must be expressed as: ■ Calculate ground distance based on map scale and map distance

● Example: In a 1:50,000 map, the map distance is 2 inches; Ground distance: 2*50,000 = 100,000 inches = 100,000/63360 = 1.57 miles (note 1 mile = 63360 inches) ○ How do you convert a verbal scale to RF? ■ Converting an R.F. scale to a verbal scale is very easy: simply select ONE unit and apply it to BOTH map and ground numbers. A representative fraction of 1:63,360 can be expressed with the verbal scale "1 inch to 63,360 inches." Since 63,360 inches are equal to 1 mile, you can also express this as '1 inch to 1 mile." ■ How about 1:72,000? 1:72,000 means that one inch on map equals to 72,000 inches on the ground (or, remember you can use another unit: "one centimeter equals 72,000 centimeters" would also work). Now we need to convert the small unit (in this case, inch) on the ground distance to some common large unit (e.g., miles). Assuming we want to use mile as the unit, then we just divide 72,000 by 63,360 (since 1 mile = 63,360 inches) ○ Which map scale is larger, 1:24,000 and 1:50,000? Which one would depict great detail? Which one would cover large area? ■ Large fraction = Small Denominator = large scale ■ Large scale map: displays a small portion of the earth’s surface with great detail ■ Small scale map: displays a large area but less detail ○ Self- Assessment 4: Map Scale ■ 1) Two bus-stops 800 m apart measures 2 cm on a map.The map scale is 1: n. What is the value of n? ● 40000 (2 cm rep 800 m = 80000 cm, 1 cm rep 40000 cm) ■ 2) A hiking trail measures 8 cm on a 1: 50000 map. How long is the hiking trail in km? ● 4 ■ 3) With a small scale map you could ● Plan a long drive ■ 4) Which of the following representative fractions on a map would show the largest scale? ● 1:1000 ■ 5) Match the appropriate map scale to the corresponding two maps (A and B). ● Map B shows larger spatial extent but less details, should be with smaller map scale. In contrast, map A, which shows smaller spatial extent but more details, should be with a larger map scale.

7. Global Positioning Systems ○ GPS is a space-based satellite navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. ○ GPS positioning steps: ■ 1) Satellites send signals containing location and time to the GPS receiver. ■ 2) The GPS receiver searches and obtains signals from at least three satellites. The more satellites it finds, the higher accuracy it can achieve. ■ 3) The GPS receiver a) calculates its distance to the satellites, and b) determines its location using the method of “trilateration”. ● → Trilateration: The process used by GPS to determine the location of a receiver by measuring the distances to three or more satellites. ○ How many satellites are required for 2D fix (Determine horizontal position) and 3D fix (Determine horizontal and vertical position)? ■ 2D Fix (Determine horizontal position): at least 3 satellites ■ 3D fix (Determine horizontal and vertical position): at least 4 satellites ○ Source of errors: ■ Satellite clocks: 1.5 to 3.6 meters ■ Selective availability: The intentional degradation of GPS signals by the U.S. military. SA was turned off in 2000.Eliminated by May 2000 ■ Atmospheric conditions: Ionosphere (5 to 7 meters) or Troposphere (0.5 to 0.7 meters) ● Errors due to atmospheric refraction ■ Multipath error: signals reflected off surrounding buildings, trees (0.6 to 1.2 meters)

○ Ways to minimize errors: ■ Differential GPS: a correction method that uses a series of base stations at known locations on the ground to provide a correction of GPS positional information. ■ Wide Area Augmentation System (WAAS)- not required-- a satellite-based, new “real-time” DGPS correction method, developed by the Federal Aviation Administration (FAA) to obtain a more accurate position information for aircraft. ■ Local area system (LAAS): is used for aircraft approaches and landings. Combined with the WAAS system, it can provide seamless navigation coverage for aircraft. ○ What is selective availability? ■ Intentionally degrade signals by DOD. ■ The U.S. Department of Defense, worried about enemies making use of GPS, instituted Selective Availability (SA) with the goal of intentionally making the positioning information less accurate. This intentional degradation of GPS signals is called selective availability. When SA was active, civilian GPS receivers could only get position accuracy within 100 meters. This, naturally, limited GPS applications in the civilian sector – who wants to try to land an airplane using GPS when the runway's location could be 100 meters off? ■ SA proved costly to the DOD during the 1991 Gulf War and the 1994 Haiti campaign, because the military quality GPS devices were in short supply. After the Gulf War, the U.S. Army announced it would install GPS in all armored vehicles to help minimize friendly fire incidents (w...