The scale of a chart is a ratio of a distance on the chart and the actual distance on the ____________________________________.

The scale of a chart represents the relationship between a distance measured on the chart and the corresponding distance on the actual ground or surface of the Earth. This means that if a specific distance is measured in centimeters or inches on the chart, the scale tells you how many corresponding units on the actual surface it represents, thus providing a crucial reference for navigation.

Understanding this concept is vital for mariners and anyone using charts as they rely on this information to navigate effectively. While water bodies, sea levels, and land all play roles in navigation, the ground is the most accurate term to encompass all types of surfaces being represented, as it includes all land and sea navigational situations. In essence, the ground reflects the real-world distances that navigators must consider while planning and executing their routes.