‘Learning Ace makes it easier for me focus on what I want to learn and not what the average search engine suggests I should learn.’ 1June 15, 2004 Map Projections for the Great Lakes Geographic Information System (GLGIS) Project 1. What is a Map Projection? 2. Visualizing a Map Projection 3. Distortions in Planar Space 4. Why use a Map Projection? 5. Projected Coordinate Systems 6. Classes of Map Projections 7. GLGIS Map Projections 8. Implementing a GLGIS Map Projection 9. Map Projections a Lake at a Time 10. Additional Resources 1. What is a Map Projection? Map projections are mathematical transformations used to portray the surface of the Earth, a three-dimensional body, on a flat, two-dimensional surface. Through mathematical formulae, coordinates are transformed from three-dimensional, angular values (i.e., latitude, longitude) to two-dimensional, planar values (e.g., feet, meters). 2. Visualizing a Map Projection* One easy way to understand how map projections alter spatial properties is to visualize shining a light through the Earth onto a surface, called the projection surface. Imagine the Earth’s surface is clear with the graticule (i.e., a graphic representation on a map of the network of parallels and meridians (latitude and longitude) that subdivide the Earth’s surface) drawn on it. Wrap a piece of paper around the Earth. A light at the center of the Earth will cast the shadows of the graticule onto the piece of paper. You can now unwrap the paper and lay it flat. The shape of the graticule on the flat paper is very different than on the Earth. The map projection has distorted the graticule. 3. Distortions in Planar Space** Inevitably, some distortions of shape, distance, direction, scale, and/or area result from the process. Many projections have been developed, some minimize distortions in some of these properties at the expense of other properties, while some projections attempt to only moderately distort all of these properties. E.G. please always turn off your cell phone or put it on vibrate mode for class A kind reminder on distractions such as phone use, noise (see syllabus). Please allow fellow students to focus. GIS for environmental management Dr. William James Smith, Jr. Assistant Professor scales. A third type of transformation is the transformation of cartographic objects themselves via their dimensions. Because Learning Ace is a 100% student-focused web destination that leverages our proprietary adaptive search and recommendation technologies and our instructor/publisher relationships to develop an insanely valuable resource to students at each learning point of their coursework. Discover, Browse and Learn. Source.