Learning Module: Selecting Projections for Spatial Analysis
Purpose
This module exposes you to the various projection systems that are available for performing spatial analysis.
Learning Outcomes
- Define the terms:
- Select the appropriate projection system based on a region of interest:
- Geographic
- Universal Transverse Mercator (UTM)
- State Plane
- North American Alber's Equal Area
- North American Lambert Conformal Conic.
- Correctly project data sets to a new spatial reference system including a "Datum Transform" when needed.
- Demonstrate an understanding that no matter how we project spherical data (3D) onto a plane (2D), there will be distortion.
Reading (optional)
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Reading: Chapter 3
- Only read "Datum Transformations", "Vertical Datums", and "Dynamic Heights" if you really want to!
Presentations/Discussions
Activities
Understanding how projections work is a challenge for almost all students. Two methods for getting a better understanding for how we convert spherical data to planar data are:
- Find an "American Educational Map Projection Model" and play with the overlays on the globe until you can visualize data on a sphere being "projected" onto the two dimensional overlays.
- Purchase an inflatable globe and then cut it open along a meridian line (line of longitude). Notice that it will not lay flat. Make additional cuts trying to make the earth lay on a flat surface. This is actually quite difficult even though the globe was created using strips that were originally flat!
Both of these activities help illustrate a key concept that no matter how we "project" data there will always be some distortion.
Additional activities
- Visit the Wikipedia pages for some of the projections described here.
Lab
