Map Projection

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INTRODUCTION:

       Cartography is the science of map-making.  It comprises many problems and techniques, including: South America in selected projections at identical scale. Which projection is best? Which is right? The short answer is none, at least not all the time. Even if a single projection is used, just switching the aspect can also radically reshape the continents. Measuring Earth's shape and features are collecting and storing information about terrain, places and people adapting three-dimensional features to flat models (my main concern) devising and designing conventions for graphical representation of data printing and publishing information. The term map projection can be thought of literally as a projection. If we were to place a light bulb inside a translucent globe and project the image onto a wall - we'd have a map projection. However, instead of projecting a light, cartographers use mathematical formulas to create projections.

Conformity - the shapes of places are accurateDistance - measured distances are accurateArea/Equivalence - the areas represented on the map are proportional to their area on the earthDirection - angles of direction are portrayed accurately

My Own Projection:I have always liked playing with world maps and wondered how computers could be used for mapping. I spent a good time deducing formulas for projecting radius, latitude and longitude into cartesian x and y. Of course, I could only draw coordinate grids until the day I got a public-domain database of geographical coordinates (at first my PC-XT computer spent over one hour to draw a rough map).

TYPES OF MAP PROJECTION:

Cylindrical Equal Area:

Cylindrical Equal-Area projections have straight meridians and parallels, the meridians are equally spaced, the parallels unequally spaced. There are normal, transverse, and oblique cylindrical equal-area projections. Scale is true along the central line (the equator for normal, the central meridian for transverse, and a selected line for oblique) and along two lines equidistant from the central line. Shape and scale distortions increase near points 90 degrees from the central line.Behrmann ‘s Cylindrical Equal-AreaBehrmann's cylindrical equal-area projection uses 30:00 North as the parallel of no distortion.

Gall's Stereographic Cylindrical:

Gall's stereographic cylindrical projection results from projecting the earth's surface from the equator onto a secant cylinder intersected by the globe at 45 degrees north and 45 degrees south. This projection moderately distorts distance, shape, direction, and area.

Mercator:

The Mercator projection has straight meridians and parallels that intersect at right angles. Scale is true at the equator or at two standard parallels equidistant from the equator. The projection is often used for marine navigation because all straight lines on the map are lines of constant azimuth.

Miller Cylindrical:

The Miller projection has straight meridians and parallels that meet at right angles, but straight lines are not of constant azimuth. Shapes and areas are distorted. Directions are true only along the equator. The projection avoids the scale exaggerations of the Mercator map.

Oblique Mercator:

Oblique Mercator projections are used to portray regions along great circles. Distances are true along a great circle defined by the tangent line formed by the sphere and the oblique cylinder; elsewhere distance, shape, and areas are distorted. Once used to map Landsat images (now replaced by the Space Oblique Mercator), this projection is used for areas that are long, thin zones at a diagonal with respect to north, such as Alaska State Plane Zone 5001.

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