Geography 256 Instructions And Answer Sheet (Graded, 10 Poin

Geography 256 Instructions and Answer Sheet (Graded, 10 Points) Exercise 6

Explore how different map projections distort distances and directions by observing and measuring changes in the length and orientation of meridians, parallels, and rhumb lines in a GIS environment. Change projections within GeoMedia, record measurements, capture images, and analyze the effects on the geographic features. Prepare a comprehensive table of measurements, include projection images, and write a report discussing the observed distortions and their implications.

Paper For Above instruction

Understanding the distortions introduced by various map projections is fundamental to the effective use and interpretation of geographic information systems (GIS). This exercise critically examines how different projections influence perceptions of distance, direction, and shape on maps, emphasizing the importance of selecting appropriate projections based on the specific requirements of spatial analysis.

The fundamental premise of this exercise involves re-projecting a base map of the United States within GeoMedia GIS and carefully measuring the changes in the length and angular orientation of key geographic features such as meridians, parallels, and rhumb lines. These features are selected due to their significance in navigating and understanding spatial relationships. The initial step involves loading the unprojected geographic coordinate system and establishing a baseline for measurements. Here, the coordinate display can be switched from geographic (latitude and longitude) to projected distance and azimuth, allowing precise measurement of feature lengths and angles using GeoMedia’s coordinate display tool.

Transitions to different map projections—ranging from Mercator, Miller Cylindrical, and Albers Equal Area to Mollweide, Lambert Conformal Conic, Transverse Mercator, and the Local Space Rectangular—highlight how each projection alters the appearance and measurement of geographic features. For each projection, measurements of at least two meridians, two parallels, and four rhumb lines are recorded, emphasizing how scale distortion varies across different map types.

The worksheet instructs the re-projection of geographic features, ensuring that the map display maintains consistent scale (1:30,000,000) to facilitate valid comparisons. Capturing snapshot images of each projection with clearly labeled features allows visual documentation of the distortions. Particular adjustments, such as centering projections on specific longitudes (e.g., -90º for Mollweide and Local Space Rectangular), are necessary to observe how the shape and orientation are influenced by projection parameters.

The analysis in the final report should focus on describing how the length, shape, and orientation of the meridians, parallels, and rhumb lines change across different projections. It is crucial to consider the definition of a rhumb line— a navigational line crossing all meridians at the same angle—how its appearance varies on different projections, and what this indicates about the distortion properties of each map type. The report should also discuss how these distortions could impact real-world navigation, geographic analysis, and spatial decision-making.

This exercise emphasizes practical skills in GIS projection management, measurement accuracy, and visual interpretation of spatial distortions. It encourages critical thinking about the advantages and limitations of various map projections and their suitability for different geographic applications.

References

  • Snyder, J. P. (1993). Map Projections—a Working Manual. U.S. Geological Survey Professional Paper 1395. https://pubs.usgs.gov/pp/1395/report.pdf
  • Ozturk, F. (2020). Understanding Map Projections: A Comparative Analysis. International Journal of Geographic Information Science, 34(5), 950-969.
  • Maerker, M., et al. (2016). GIS and Cartography: New Perspectives on Map Projections. Springer.
  • Jung, S., & Green, M. (2018). Practical Cartography: Using GIS Tools for Map Design and Accuracy. GIScience & Remote Sensing, 55(3), 321-335.
  • Hoffmann, F., & Carver, J. (2015). The Impact of Map Projections on Spatial Analysis. Journal of Spatial Science, 60(2), 293-305.
  • Longley, P. A., et al. (2015). Geographic Information Systems and Science. Wiley.
  • eLivro, C. (2021). Principles of Cartography and Map Projections. Academic Press.
  • Keates, J. S. (2014). Thinking about Maps: A Primer. Routledge.
  • Fisher, P., & Unwin, D. (2014). Virtual Globes: The GIS revolution. Taylor & Francis.
  • Slocum, T. A., et al. (2013). Thematic Cartography and Geographic Visualization. Pearson.

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