Precision vs Accuracy

In this chapter, you learned about the difference between accuracy and precision. Accuracy is the degree to which information on a map matches true or accepted values. It is a measure of truth or correctness. Precision is the exactness of measurement. It represents the level of detail, the level of measurement, the level of repeatability, or the meticulousness of description. Accuracy sometimes improves with precision, but a high degree of precision should not be an automatic indicator of accuracy.

In ArcMap, zoom to the San Francisco Bay. In the Table of Contents, uncheck all of the boxes next to each layer. Then, turn them on and off, one at a time. Make a comparison between the three layers regarding accuracy and precision.

An image of the San Francisco Bay
You can view one layer at a time by checking and unchecking the boxes. Click to view a larger sized image.

In Microsoft Word, add an H1 heading that says, “Visual Inspection.” Below the h1 heading, record the answers to the following questions.

  1. Which dataset has the highest level of precision?
  2. Based on your understanding of precision and accuracy, is the dataset with the highest level of precision the most accurate? Explain your answer.