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Yuji Murayama |
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Division of Spatial Information Science |
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Brandon M. Vista |
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Teaching Assistant |
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Is process of associating data points with
specific locations on the earth’s surface. |
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It encompasses the definition, the
physical/geometric constructs and the tools required to describe the
geometry and motions of objects near and on the Earth`s surface. |
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Maps are a common source of input data for a
GIS. Often input maps will be
in different projections, requiring transformation of one or all maps to
make coordinates compatible. |
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GIS are used for projects of global or regional
scales so consideration of the effect of the earth's curvature is
necessary. |
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Monitor screens are analogous to a flat sheet of
paper, and need transformations from the curved surface to the plane for
displaying data. |
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Is the most comprehensive and powerful method of
georeferencing |
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Metric, standard, stable, unique |
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Uses a well-defined and fixed reference frame |
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Based on the Earth’s rotation and center of
mass, and the Greenwich Meridian |
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Latitude represents an angular distance along a
meridian north or south from the equator. |
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Longitude is an angular distance of a point on
the earth's surface east or west of an arbitrarily defined meridian,
usually the Greenwich meridian (Greenwich, England). |
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A line of longitude running vertically from the
north pole to the south pole, but unlike lines of longitude, meridians
terminate at the poles. |
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The Prime Meridian, currently called the
Greenwich Meridian, runs through Greenwich, England, was agreed in 1884 as
being the central meridian from which all other meridians would be
referenced to in order to calculate longitude. |
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Because the earth is three-dimensional, some
method must be used to depict the map in two dimensions. Therefore such
representations distort some parameter of the earth's surface, be it
distance, area, shape, or direction |
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A map projection is a method of representing the
earth's three-dimensional surface as a flat two-dimensional surface. This
normally involves a mathematical model that transforms the locations of
features on the earth's surface to locations on a two-dimensional surface. |
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Any projection must distort the Earth in some
way. Distortion properties are
usually classified according to what is not distorted on the map as
follows: |
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Conformal property: Angles between lines on the
curved reference surface are identical to the angles between the images of
these lines on the map; Shapes of small features are preserved: anywhere on
the projection the distortion is the same in all directions |
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Equal area property: area enclosed by the lines
in the map are preserved but shapes are distorted |
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Equidistant property: length of a particular
lines in the map are preserved |
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Conceptualized as the result of wrapping a
cylinder of paper around the Earth |
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Example: Mercator Sinusoidal |
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Conceptualized as the result of wrapping a cone
of paper around the Earth |
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Example: Lambert Conformal Conic |
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Conceptualized as the result of projecting a
spherical surface onto a plane |
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Example: Gnomonic |
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Developed in 1947 by US army |
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A type of cylindrical projection but unlike the
normal cylindrical projection, it is called Transverse Mercator because the
cylinder is wrapped around the Poles, not on the Equator. |
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Currently, the WGS84 ellipsoid is used as the
underlying model of the Earth in the UTM coordinate system. |
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Implemented as an internationally standard
coordinate system |
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Longley, Paul et. al (2005). Geographic Information Systems and
Science. 2nd ed. England: John
Wiley & Sons, Ltd. |
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de By, Royce A., et. al. (2001). Principles of
Geographic Information System: An Introductory Textbook. Royce de By (ed).
Netherlands: International Institute for Geoinformation Science and Earth
Observation (ITC). |
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Thank you for your attention! |
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