Chapter 4: Map Scale and Spatial Reference Systems

Table of Contents

  1. Overview
  2. Map Scale
  3. Spatial Reference Systems
  4. Geographic Coordinate Systems (GCS)
  5. Projected Coordinate Systems (PCS)

Chapter 4 Tutorials


Most people have the idea that coordinate systems are static, unchanging definitions of where they are. You can log on to google maps and look up your latitude and longitude coordinates and feel confident that these numbers have a universal meaning that does not change. In reality, the numbers you see on google maps are just one of many versions of latitude and longitude coordinates that can define your location.

Chapter 4 presents how distance and location are defined and communicated using map scale and spatial reference systems. Determining a position on earth in a way that is meaningful to others is a difficult challenge. In part, the difficulty is due to the differences in map projections and datums used across the world, which can change longitude and latitude coordinates in different ways. It may seem like a trivial detail, yet boundary definitions and positional information can have significant legal, political, and military consequences.  Recall that a datum is calculated from a reference ellipsoid, of which there are many, and this changes the way a position on the earth is specified. In addition, there are many ways other than latitude and longitude to reference a point on the earth, and we’ll look at some of those in this chapter.

Learning Outcomes

  • Explain the difference between map scale versus scope
  • Express three ways of representing scale
  • Recognize large-scale and small-scale maps
  • List common distance equivalents
  • Perform scale conversions
  • Determine an unknown scale with a variety of references
  • Describe early land partitioning systems
  • Identify the differences between geographic and projected spatial reference systems
  • Demonstrate correct notation for a variety of spatial reference system