Final answer:
The gradient height for open country areas varies widely, and it describes the slope or elevation change across a landscape. This gradient is inversely proportional to the map scale and determined by the terrain's topography.
Step-by-step explanation:
The phrase ‘gradient height for open country areas’ likely refers to the slope or elevation change across a landscape in terms of mapping or physical geography. The specific gradient height for open country areas can vary significantly depending on the terrain. However, in general, gradients can range from flat areas with minimal elevation change to mountainous regions with gradients of several thousands of meters.
The gradient height is inversely proportional to the map scale and will differ based on whether an area has flat or steep topography. For example, topographic points representing an altitude from 4,000 meters to 6,000 meters shows that the density of the air decreases by approximately 0.1 kilograms/cubic meter for each of the next 1,000 meters, indicating a reduction in air density with elevation.