Exploring Error and Uncertainty Related to Datums and Projections Using ArcGIS

Evaluate Distortion Patterns in Map Projections

Table of Contents

  1. Exploring Error and Uncertainty Related to Datums and Projections Using ArcGIS
  2. Skill Drill: Setting Up Your Workspace
  3. Skill Drill: Downloading Data from Natural Earth
  4. Skill Drill: Connect to Your Workspace Folder in ArcMap
  5. Creating a File Geodatabase
  6. Creating Feature Classes from Shapefiles
  7. Adding XY Data using the ArcCatalog Window
  8. Skill Drill: Creating Indicatrices Using the Buffer Tool
  9. Evaluate Distortion Patterns in Map Projections
  10. Measuring Scale Distortion
  11. Skill Drill: Evaluate and Measure Distortion
  12. Troubleshooting Datum Shift
  13. Repairing Corrupted Data Using the Define Projection Tool
  14. Skill Drill: Repairing Incorrect Coordinate System Definitions

As learned previously, a map projection is the geometric transformation of the spherical earth onto a flat plane using mathematical equations. One cannot perform this transformation without a high degree of distortion. However, some map projections can maintain a high degree of accuracy of particular geometric characteristics called preserved properties. Distortion occurs in one or more of the following properties:

  • Area
  • Shape
  • Distance
  • Direction
  • Continuity

A map projection may be able to maintain more than one of these properties, but no map projection can preserve all of them at once.

Take a moment to capture a screenshot of your ArcMap window. You can do this by pressing the Alt key and the Print Screen key on your keyboard while the ArcMap window is active.

Alternatively, you may use the Microsoft Windows Snip and Sketch app to capture a portion of your screen.

Open a blank Microsoft word document. In Microsoft Word, press Ctrl V to paste the screenshot into the document. Right-click the image and choose Insert Caption (Figure 2.31). Type the name of the map projection as the figure caption. Then, write down the answer to the following questions:

  1. Which of the five properties appear to be preserved based on the size and shape of the indicatrices?
  2. Which of the five properties appear to be distorted based on the size and shape of the indicatrices?
  3. Where on the map does there appear to be minimal distortion?
  4. Where on the map does there appear to be the most distortion?
Figure 2.31: You should be prepared to discuss the answers to these questions at a later time. Double-click or tap twice to view the image in a larger size.

Save your Word document to your final folder. You answer these same questions for other map projections in a later step.