What is the meaning of hatchures on contour lines?

Hatchures on contour lines are used to indicate depressions or lower areas in the terrain on a map. These are typically shown as short, parallel lines that are drawn on the inside of a contour line, creating a visual representation of a dip or indentation in the landscape. By identifying these hatchures, a user can quickly discern where the ground falls below the surrounding elevation, which is crucial for navigation and planning in search and rescue operations, as well as for understanding the geography of an area. This feature helps to highlight areas that might be significant for identifying hazards or areas of interest during a mission.