emr21 lab 3 objectives: download gis data from the web manipulate the data in arcgis, export to ai...

EMR21 Lab 3

Objectives:• Download GIS data from the web• Manipulate the data in ArcGIS, export to AI

format• Design in Adobe Illustrator

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October 2 - 4

End of lecture 1

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Map projections: Taking a 3d object and modeling it in 2 dimensions

A common analogy: peeling an orange

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Map projections – representing a 3d sphere on a 2d plane.

Map projections distort at least one of these: distance, direction, shape, or area.

Every projection has its own set of advantages and disadvantages.

The mapmaker must select the one best suited to the needs, reducing distortion of the most important features for the area of interest.

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Map projection – representing a sphere on a 2d plane.

A light source projected through a sphere.

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Cylindrical projection – projected onto a cylinder tangent to the globe. E.g. the Mercator projection created by Gerardus Mercator in the 1500s.

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Map projection: Cylindrical• Distances along the Equator are true• Moving poleward, shape is significantly distorted.

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Conic projection – projected onto a cone which passes through the globe.

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Map projections are designed to minimize distortion for specific areas on Earth. The conic projection shown here minimizes distortion for the lower 48 US states.

Albers Equal Area Conic projection – All areas on the map are proportional to how they are on the globe.

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Cubic projection

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Fuller projection (polyhedron)

Thousands of years before present

Human Migration

Winkle-triple projectiona good choice for global maps

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Most GIS software allows one to changes the map’s projection to best suit the needs of the map to be made. 14

Let’s do the lab….

Download the Lab3_US_Map.docx on the class website, Lab3 page.

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