Map Projection

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Our title of the project is "projection", which represent by Johnny.Lu73379018 and Grant.Tong73382012. Ok, first of all. let me explain what is map projection.  Map projections are kind of systematic transformations that allow us to view the area of land very clarity on  a flat map.  According to mathematically speaking, map projections are transformations of geographic co-ordinates (latitude, longitude) into the Cartesian (x, y) co-ordinate space of the map. Some map projections can be constructed geometrically. Here is the beauty of map projection,  because all map projections can be represented by mathematical equations that convert geographic co-ordinates into map co-ordinates; however, this is also the hard part for us to calculate the co-ordinates. Therefore , we are just gonna focus on 3 main category projection we have  used most  in our life.

1. Mercator Projection

Making a  limpid terrestrial globe inside the limpid cylinder, put the light source inside the terrestrial globe, then the projection of the rectangle, which intersected by longitude and latitude is the first graph we draw in  first link. However, since the distance between  longitude and latitude in high latitude area is much wider, so the area of projection of the land  in high latitude area will much bigger than the real area. we will explain this point by some graphics below in the second link. Also, we will provide some information of calculations in the third link.

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2.Lambert Projection

Making a  limpid terrestrial globe inside the limpid coin, put the light source inside the terrestrial globe, then the projection of the rectangles and triangles,  which intersected by longitude and latitude is the first graph we draw in  first link. Also the area of projection of the land  in high latitude area will much bigger than the real area. we will explain this point by some graphics below in the second link. Also, we will provide some information of calculations in the third link.  Therefore, we can conclude that Lambert projection of land approach the real area of land  in the middle latitude area. we usually use this projection in a topographic chart, aviation chart  in the middle latitude area.

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3.  Azimuthal Equidistant Projection & Azimuthal Equal  area  Projection

a) Azimuthal Equidistant Projection

Category:  mathematical projection.

Step1: Use a paper to cut the north pole or south pole of terrestrial globe.

step2: Use the point of tangency as a center to draw the woof, so every woofs got the same arc of concentric circle, which radius is equal

the distance of every woofs to the point of tangency.

step3 : Use the point of tangency as a center to draw the meridian, then every meridian is the radioactive rays, which intercept the center.

Feature: United Nation use this way of projection

every woof get the same distance

b)Azimuthal Equal  area  Projection

Category: Mathematical projection, equal-area projection

Step1: Use a paper to cut the north pole or south pole of terrestrial globe.

step2: Use the point of tangency as a center to draw the woof, so every woofs got the same arc of concentric circle, which radius is

1= 2r sin  ((90¢X¡Ð Ø)/2)

step3 : Use the point of tangency as a center to draw the meridian, then every meridian is the radioactive rays, which intercept the center.

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Represent by Johnny.Lu and Grant.Tong

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