In photogrammetry, which variable represents the altitude of the aircraft above datum in the formula S = f / (H - h)?

In photogrammetry, the formula S = f / (H - h) deals with the relationship between the scale of the photograph (S), the focal length of the camera (f), and the altitudes involved in the imaging process. In this context, H represents the altitude of the aircraft above a reference level, commonly referred to as the datum, while h signifies the height of the object being measured above the same datum.

To understand why this variable is vital, altitude is crucial in determining the scale of the images produced. Higher altitudes lead to a smaller scale (less detailed images) because the perspective is broader, while lower altitudes yield a larger scale with more detail due to the closer proximity to the subject. Thus, H reflects the operational height of the aircraft, which significantly influences the interpretations and measurements taken from photogrammetric data. This is why identifying H as the variable for altitude is essential in understanding how photogrammetry works and how data is gathered and interpreted effectively.