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16 Cards in this Set
- Front
- Back
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Most fundamental geography
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Location
Distance Direction Area Shape Pattern |
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A simplification
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For many purposes, we can consider the earth as a sphere.
In reality of course, it is not a perfect sphere Ellipsoidal, rather than a sphere Imposed on that ellipsoid are mountains, valleys, ocean basins, etc. |
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The earth as a sphere
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Circumference of 24900 miles.
Equal circumference between poles and around equator. |
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Question
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The earth is 24,900 miles in circumference at the equator. If that is divided into 360 degrees like any circle …
How many miles per degree are there? approximately 69 How many kilometers per degree are there? approximately 111 |
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Earth in reality
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An ellipsoid
Wider at equator Narrower at poles |
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Geography on a sphere
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How do we determine these on a spherical earth?
Location Distance Direction |
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Parallels and Meridians
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We divide the globe by parallels and meridians
There are an infinite number of parallels and meridians. We assign latitude to parallels We assign longitude to meridians Location is the junction of the parallel and meridian at that spot. |
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Latitude
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Parallels
Measured from equator. Requires North or South to be complete |
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Longitude
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Meridians
Measured from Greenwich Observatory Need to give East or West to make the reference complete |
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Two and Three dimensions
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To give a geographic reference using latitude and longitude
Two dimensions. Requires a latitude and longitude Three dimensions. Add an elevation. |
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Location -- Emphasis
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To give a location
Latitude, longitude Don’t forget hemisphere indicator Add elevation if needed |
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Hemisphere indictors
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N, S, E, W are obvious
Signs are used too Latitude + is always North - is always South Longitude convention depends on application + is usually East - is usually West Aircraft navigation apps sometimes switch them |
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What is a degree?
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The earth is divided into 360 degrees of latitude and longitude. If the circumference of the earth is 24900 miles, that means that one degree is about 69 miles.
How many kilometers is this? 111 |
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Finer divisions or parts
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We can divide one degree into 60 pieces
These are called minutes We indicate minutes with ‘ or an m Furthermore, we can divide one minute into 60 pieces These are called seconds We indicate seconds with “ or an s We frequently give fractional minutes or seconds. |
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Finer resolution references
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If one degree is 111 kilometers at the equator
How big is one minute? 111 km / 60 How big is one second? above / 60 again |
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Conversions
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To convert from one to another, you are always dividing or multiplying by 60 and playing with remainders.
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