Geography Chapter 2 – Flashcards

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the surface of the earth
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The focus of the geographer is
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the map
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Most important tool of a geographer?
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mapping them
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What is often the first essential step toward understanding the spatial distributions and relationships of geographic features?
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the globe
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What is the best way to show the Earth as a whole
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accurately convey's the spherical shape of the Earth as well as show without distortion, the spatial relationships of Earth's surface, while maintaining correct size, shape, distance, and direction relationships of features around the planet
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A well made globe
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constructed at a very small scale and can't show much detail
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A globe does have limitations
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a flat representation of Earth, shown reduced in size with only selected features or data showing
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What is a map?
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what is where: distance, direction, size, shape in horizontal, or two dimensional, spatial relationships
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The map is good for showing
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a map with a theme. For example, street patterns
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What is a thematic map?
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no map can be perfectly accurate because it is impossible to portray the curved surface of Earth on a flat map without distortion
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Maps have limitations as well
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1) how much of Earth is being shown on the map (ex: these distortions are always significant on a world map, but less so on a map showing a very limited region of the Earth) 2) the scale of map
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The extent to which the geometric impossibility of flattening a sphere without distortion becomes a problem on a map depends on two related variables
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a map scale
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Because a map is smaller than the portion of Earth's surface it represents, in order to understand the geographic relationships depicted on that map, we must know how to use
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the relationship between distance measured on a map and the actual distance that represents the Earth's surface
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The map scale describes
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measure distance, determine area, and compare size
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Knowing the scale of the map makes it possible to
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because the Earth's surface is curved and map's are flat
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Scale can never be perfectly correct over an entire map, why?
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a single scale will most likely do it.
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If the map is of a small area, how many scales should be used?
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there will be significant scale differences from one part of the map to the other and may need different scales for different latitudes
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If the map is showing large portions of the Earth's surface, what happens to the map scale?
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graphic scale, fractional scale, and verbal scale
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There are three ways to portray map scales that are widely used
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uses a line marked off in distances to represent actual distance on Earth's surface
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What is a graphic map scale?
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You measure off the distance between two points on the map and then convert using the graphic map scale
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How do you use a graphic map scale?
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a direct reading of actual distance
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Using the graphic map scale will give you
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simplicity and it remains correct when the map is enlarged or reduced in size
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The advantage of a graphic map scale
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it conveys the relationship between distance measured on the map and the actual distance that represents on Earth with a fraction or ratio
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What is a fractional map scale
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representative fraction
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This fraction used in fractional map scale is called
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1/63,360 or 1:63,360: this notation means that 1 unit measure on the map represents an actual distance of 63,630 units on earth
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An example of a fraction in a fractional map scale
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Aka: word scale, states that in words the relationship between the distance on the map and the actual distance on Earth's surface, such as "one centimeter to ten kilometers"
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What is a verbal map scale?
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A verbal scale is a mathematical manipulation of the fractional scale. Ex: there are 63,360 inches in a mile, so on a map with a fractional scale of 1:63,360, we can say 1 inch represents 1 mile
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How is a verbal map scale similar to a fractional map scale?
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One that has a relatively large representative fraction or the denominator is smaller
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What is a large scale map?
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One that has a relatively small representative fraction or the denominator is larger
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What is a small scale map?
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a system in which the spherical surface of Earth is transformed for display on a flat surface
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What is map projection?
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mathematically transferred the features from the sphere to a flat surface
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How are most map projections created today?
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there will always be distortion of shape, relative area, distance, and/or direction. You can control some of these but never all
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What needs to be understood no matter how map projections are done?
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equivalence and conformality
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Cartographers often strive to maintain accuracy either of size or shape using map properties known as
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In an equivalent map projection or equal area map projection, the correct size ratio of area on the map to the corresponding actual area on Earth's surface is maintained over the entire map
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What is equivalence?
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misleading impressions of size are avoided
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Why are equivalent map projections desirable?
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difficult to achieve on small scale maps because correct shapes must be sacrificed in order to maintain proper area relationships
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What is the down side of equivalence?
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A conformal map projection is one in which proper angular relationships are maintained across the entire map so that the shapes of features such as coastlines are the same as on Earth
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What is conformality?
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They show correct shapes on a map. It is impossible to depict true shapes for large areas such as a continent, but they can be approximated, and in practice for small areas we can say conformal maps show correct shapes
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So what does conformality achieve?
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meridians and parallels
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All conformal projections have ____ and ____ crossing each other at right angles
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the size of an area must often be considerably distorted to depict proper shape. The scale will have to change from one region to another
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What is the problem with conformal projections?
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a compromise map projection
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Except for maps of very small areas, where both properties can be closely approximated, conformality and equivalence cannot be maintained on the same projection, and thus the art of mapmaking is often an art of compromise. What kind of projection is neither equivalent nor conformal, but instead balances reasonably accurate shapes with reasonably accurate areas?
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a Robinson projection
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What is an example of a compromise map projection?
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its obtained by mathematically "wrapping" the globe with a cylinder of paper in such a way that the paper touches the globe only at the globe's equator
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What is a cylindrical projection
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tangent; the circle of tangency
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This type of wrapping, we say it is _______ to the globe at the equator and the equator is called the ______ __ _______
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they will form a perfectly rectangular grip on the map and having the equator as the tangency line produces a right angled grid (meridians and parallels meet at right angles) on a rectangular map
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In cylindrical projection, what happens to the curved parallels and meridians
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No
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Is there size distortion at the circle of tangency?
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size distortion increases progressively with increasing distance from this circle
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Is there size distortion anywhere else on these maps?
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Mercator projection
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What kind of projection can we clearly see this issue?
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1569
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The Mercator projection was created in _____ and is till the go to for many, most famous map
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a conformal map projection designed to facilitate oceanic navigation
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What is the Mercator projection?
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it shows loxodromes as straight lines
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What is the prime advantage of a Mercator map?
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also called a rhumb line, a curve on the surface of a sphere that crosses all meridians at the same angle and represents a line of constant compass direction
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What is a loxodrome?
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a navigator first plots the shortest distance between origin and destination on a map projection in which great circles are shown as straight lines and then transfers them to a Mercator projection with straight line loxodromes.
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So how does one use the Mercator map?
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the shorter path of a great circle route by simply making periodic changes in the compass course
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Using the Mercator map will allow a navigator to generally take
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relatively undistorted in the low latitudes and increases rapidly in the mid and high altitudes because the meridians do not converge at the poles but instead remain parallel to each other
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How is the distortion on a Mercator map?
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he compensated for the east/west stretching by spacing the parallels of latitude increasingly farther apart so that north/south stretching occurs at the same rate
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How did Mercator attempt to maintain conformality and the maps navigational virtues?
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allows the shapes to be approximated with reasonable accuracy
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This allows what to happen to the shapes on the maps?
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proper size relationship
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What does suffer with this action?
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obtained by projecting the markings of a center-lit globe onto a flat piece of paper that is tangent to the globe at one point, usually the north or south pole, or some point on the equator.
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What is a planar projection?
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No distortion immediately around the point of tangency but increases as you move away from this point
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Planar projection and distortion?
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one hemisphere
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Typically, planar projections show only
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mapping the Arctic or Antarctic circle and focusing attention on specific regions
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What are planar projections useful for?
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obtained by projecting the markings of a center lit globe onto a cone wrapped tangent to, or intersecting, a portion of the globe. Normally, the apex of the cone is positioned above a pole, which means that the circle of tangency coincides with a parallel.
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What are conic projections
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the standard parallel of the projection
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This parallel that coincides with the circle of tangency becomes known as
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distortions are least in the vicinity of the circle of tangency and increases progressively as we get farther away
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Distortion in conic projections?
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regions of east/west orientation in the midlatitudes
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Conic projects are best suited for?
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For more than 1/4 of Earth's surface (semihemisphere)
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It is impractical to use conic projections when?
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mapping relatively small areas, such as a state or country
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What are conic projections particularly well adapted for
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also called elliptical or oval projection, roughly football shaped map, usually of the entire world, although sometimes only the central section of a pseudocylindrical projection is used for maps of lesser areas
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What is pseudocylindrical projection
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around the equator like an ordinary cylindrical projection, but then further curves in toward the poles, effectively conveying some of the curvature of Earth
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Mathematically, a pseudoclylindrical projection wraps how?
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a central parallel (usually the equator) and central meridian (often the prime meridian) cross at right angles in the middle of the map
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Where is the point of no distortion in pseudocylindrical projections?
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distortions in size and/or shape normally increases progressively as one moves away from this point in any direction
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When and where does distortion occur in pseudocylindrical projections
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drawn parallel to each eather
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In the pseudocylindrical projections, all of the parallels are
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shown as curved lines
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In the pseudocylindrical projects, all meridians, except the central meridian are
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one technique used with pseudocylindrical projections to minimize distortion of the continents is to "interrupt" oceanic regions
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What are interrupted projections?
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Goode's interrupted homolosine equal-area projection
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An example of interruped projections?
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conforomal
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It is impossible for this map to be
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very well maintained even in high latitudes
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The shapes of continental coastlines, in interrupted projections are
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interrupted or torn apart
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When global distributions are mapped, the continents are often more important than the oceans, and yet the oceans occupy most of the map space in a typical projection. A projection can be
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central meridians that pass through each major landmass - with no land area far from a central meridian
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When a projection is interrupted, it will be based on
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is greatly decreased
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By doing this, shape and size distortion
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Then we can interrupt landmasses
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What if we have a map that wants to emphasize oceans?
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title, date, legend, scale, direction, location, data source, and projection type
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Every map should contain these things
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a brief summary of the map's content or purpose. Should identity the area covered and provide some indication of content
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The title of a map should be
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indicate the time span over which the info was collected, maybe the publication date. Because most maps depict conditions or patterns that are temporary or even momentary, for the map to be meaningful, the map should indicate when the data were gathered.
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The date of a map should
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most maps use symbols, colors, shadings, or other devices to represent features or the amount, degree, or proportion of some quantity. Although some symbols are self explanatory, it is usually necessary to include a legend to help explain the symbolization
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Why is the legend necessary?
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Any map that serves as more than a pictogram must be drawn to scale, appx. Because of this, a graphic, verbal, or fractional scale is necessary
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Why do we need a scale?
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it's normally shown on a map by means of a geographic grid of parallels and meridians. If no grid is shown, direction may be indicated by a straight arrow pointing north
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Why a direction indicator?
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north arrow
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This arrow that points north is also known as
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the north pole
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The north arrow points to
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longitude and latitude
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What is the most common system of location?
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x and y grids
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What other ways do maps help individuals find location?
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thematic maps. It is useful to indicate the source of the data
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Data source is important in
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help the user assess the kinds of distortions on the map
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Notating projection type will
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any line that joins points of equal value of something
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Maps can display data many different ways. One of the most widespread techniques for portraying the geographic distribution of some phenomenon is isoline. Isoline is a generic term that refers to
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the elevation contour lines on a topographic map
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Some isolines represent tangible surfaces, such as
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temperature and precipitation, and some express relative values such as ratios or proportions
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Some isolines represent intangible features such as
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more than 100
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There are appx how many different kinds of isolines?
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used to describe radio waves
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What is isoamplitude?
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water vapor content in the air
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What is isovapor?
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a line joining points of equal elevation
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What is an elevation contour line?
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a line joining points of equal temp
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What is isotherm?
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A line joining points of equal atmospheric pressure
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What is isobar?
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a line joining points of equal quantities of precipitaiton
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What is Isohyet?
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a line joining points of equal magnetic decliniation
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What is the isogenic line?
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1) always closed lines; that is they have no ends 2) because they represent gradations in quantity, they can never touch or cross one another 3) the numerical difference between one isoline and the next is called the interval 4) isolines close together indicate a steep gradient (in other words, a rapid change); isolines far apart indicate a gentle gradient
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The basic characteristics of Isolines include
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1700; Edmund Halley, not the first time isolines were used, but first time published
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The first published map to include isolines
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do not occur in nature
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Isolines are an artificial construct
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1) raised relief models 2) elevation contours 3) digital elevation models
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What are some ways vertical landscape is portrayed on maps?
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A line on a map joining points of equal elevation
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What are elevation contour lines?
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three dimensional
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What is a raised relief model?
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computer generated shaded relief image of a landscape derived from a database of precise elevation measurements
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What is a digital elevation model?
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the parameters of the image can be readily manipulated
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What is one of the great virtues of digital elevation?
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a global navigation satellite system for determining accurate positions on or near Earth's surface developed in the 70's and 80's by the US Department of Defense to aid in navigation aircraft, guiding missiles, and controlling group troops
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What is the Global Positioning System (GPS)
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a constellation of at least 24 high altitude satellites configured so that a minimum of four or six are in view of any position on Earth. These satellites continuously transmit both identification and positioning info that can be picked up by receivers on Earth
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The GPS system is based on
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31 with backups
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How many satellites are currently active
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comparing clocks stored in both units, and then the 3D coordinates of the receiver's position are calculated thru triangulation
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The distance between a receiver and each member in a group of four or more satellites is calculated by
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the number of satellites that can be tracked and the better accuracy
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The greater the number of channels in a GPS unit, the greater
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Yes
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Are GPS's more accurate than the best base maps?
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15 meters (49 feet)
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Even the simplest GPS units determine position to within
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Wide Area Augmentation System (WAAS)
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What can increase GPS accuracy when _____ ____ ________ _____ is employed
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increase the accuracy of instrument-based flight approaches for airplanes
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WAAS was implemented to
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a position of accuracy of 3 meters (about 10 feet) about 95% of the time
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Several dozen ground based station across North America monitor GPS signals fro the satellites and then generate a correction message that is transmitted to the GPS units. With WAAS, the GPS units achieve
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They are permanently installed GPS receiving stations managed by the National Oceanic and Atmospheric Administrations. Highly accurate units that are capable of detecting location differences of less than 1 centimeter of latitude, longtitude, and elevation. Used for the long term monitoring of slight changes in the ground and surface caused by lithospheric plate movement or the bulging of magma below a volcano
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What is the Continuously Operating GPS Reference Stations (CORS)
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earthquake forecasting, ocean floor mapping, volcano monitoring and a variety of other mapping projects
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GPS has been used in
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inexpensive
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GPS is inexpensive/expensive?
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collecting data, damage assessment following natural disasters as floods and hurricanes
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How does FEMA use it?
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used by workers to catalog items found in the enormous heaps of rubble following the WTC disaster 9/11/01
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How was GPS used at Ground Zero?
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refers to any measurement of acquisition of info by a recording device that is not in physical contact with the object under study
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What is remote sensing?
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satellites!!
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What has revolutionized remote sensing?
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gather data, produce images that provide communications, global positioning, weather data, and a variety of other info for a wide range of commercial and scientific applications
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What do satellites do?
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aerial photography
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What was the only form of remote sensing that was used for geographic purposes until the 60's?
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the science of obtaining reliable measurements and mapping from aerial photographs
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What is photogrammetry?
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multicolored distortion free photographic maps prepared from aerial photographs or digital images
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What are orthophoto maps?
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greater detail
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Orthophotos can show the landscape how due to displacements being removed?
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they retain the map characteristic of a common scale that allows precise measurement of distances
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What about scale and precision?
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subtle topographic detail in areas of very low relief, such as marshlands
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Orthophoto maps are particularly useful in flat lying coastal areas because they can show
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wavelengths of radiation other than visible light
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One of the most important advancements in remote sensing came when what was first used?
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wide range of wavelengths of energy emitted by the Sun and other objects
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What is elecromagnetic radiation?
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is only sensitive to a narrow portion known as visible light, colors seen in a rainbow
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What kind of electromagnetic spectrum can the naked eye see?
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X-rays, ultraviolet radiation, infrared radiation, radio waves
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What kinds of other wavelengths of energy are there?
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uses electronic sensors or photographic film sensitive to radiation in the near infrared portion of the electromagnetic spectrum - wavelengths of radiation just longer than the human eye can see
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What is color infrared imagery?
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near infrared wavelengths
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With color IR imagery, sensitivity to visible blue light is replaced by sensitivity to
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valuable
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These images, even though they are false color images, are
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as camouflage detection because it was able to discriminate between living vegetation and the vegetation used to hide objects during the war
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How was this kind of imagery used in WWII?
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the same way
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How do we use it today?
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middle or far infrared part of the electromagnetic spectrum
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What is thermal infrared?
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conventional digital cameras or traditional photographic film
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You cannot sense thermal infrared with
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supercooled snanners
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What do we use instead?
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measures the radiant temp of objects and may be carried out either day or night
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What does thermal scanning do?
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showing diurnal temp differences between land and water, between bedrock and alluvium, for studying thermal water pollution, for detecting forest fires
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What are these photos good for?
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meteorological satellites and weather forecasting
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The greatest use for thermal IR scanning systems has been
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multispectral or multiband
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Today, most sophisticated remote sensing satellites are
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many bands of the electromagnetic spectrum simultaneously
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Multispectral instruments detect and record
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in several spectrum regions at once - visible light, near infrared, middle infrared, and thermal infrared - each useful for different applications
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Although traditional photographic film was sensitive to only a narrow band of visible radiation, a satellite equipped with a multiband instrument images the surface of the earth
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digital
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A multispectral satellite image is
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a matric of numbers, each representing a single value for a specific pixel and band
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The digital multispectral satellite image is conveyed through
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stored in the satellite, eventually transmitted to an Earth receiving station, numerically processed by a computer, and produced as a set of grey values and/or colors on a screen or hard copy printout
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The data from the digital multispectral satellite image is
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Early NASA space missions used multiband photography obtained through mulitcamera arrays. These imaging experiments were so successful that NASA then developed what was initially called Earth Resources Technology Satellite series (ERTS) and later renamed Landsat
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What is Landsat?
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Just read over this one
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Landsat 7 carries an instrument array call the Enhance Thematic Mapper Plus that provides images in eight spectral bands with a resolution of 15 meters (49 feet) in the panchoromatic band in the 6 narrow bands of visible and short infrared wavelengths, and 60 meters (197 feet) in thermal infrared.
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sensing the natural radiation emitted by or reflected from an object and are therefore characterized as passive systems
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All the remote multispectral sensing systems up to this point work by
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has its own source of electromagnetic radiation
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What is an active system?
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radar
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What is the most important active sensing used in Earth sciences?
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radio detection and ranging; senses wavelengths longer than 1 millimeter using the principle that the time it takes for an emitted signal to reach a target and then return to the sender can be converted to distance info
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What is radar?
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It can penetrate atmospheric moisture
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What is unique about radar?
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terrain analysis in places of frequent cloud cover or thick vegetation, and for meteorology, especially in the real time study and mapping of rainfall and severe weather
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Radar imagery is particularly useful for
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sonar
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The other active remote sensing system is
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sound navigation and ranging that permits underwater imaging
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Sonar is
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cartographers have been working since the early days of the Egyptians but with the intro of computer, they have advanced passed drawings. Computers have provided improvements in speed and image handling ability
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How have computers changed geography?
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geographic information systems (GIS)
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The most revolutionary technological advance in cartography in the last few decades has been
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the computer systems designed to analyze and display spatial data
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What is GIS?
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collect, store, retrieve, reorganize, analyze, and map geographic data from the real world
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Can be used to
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the link between data and the map
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GIS's are libraries of info that use maps to organize store, view, and analyze info in an intuitive, visual manner. Just as an ordinary computer database management system can manipulate rows and columns of data in tabular form, the GIS allows data management using
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organize or search the data using the map, or the map using the data
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This means the data and map are encoded, usually as numbers representing coordinates of locations at point on a grid covering the mapped area. Once the data and the map are inside the GIS, the user can
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together with a common database, with a common map scale and map projection
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One important attribute is the capability of GIS data from different maps and sources, such as field data, map data, and remotely sensed images, to be registered
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one map layer, such as rivers, to be cross referenced to another, such as geology soils, or slope
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Being able to register different info in a common database allows
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