What does the formula S = f / (H - h) represent in photogrammetry?

The formula S = f / (H - h) is utilized in photogrammetry to determine the scale of an aerial photograph at a specific elevation. In this formula, 'S' denotes the scale, 'f' represents the focal length of the camera, 'H' is the height of the camera above the datum (usually mean sea level), and 'h' is the height of the object above the same datum. By rearranging the equation, one can see that the scale is inversely proportional to the distance between the camera and the object being photographed, minus the elevation of that object. This relationship is crucial in photogrammetry to accurately measure and map three-dimensional objects based on aerial images, as it allows surveyors to understand how varying elevations affect the scale of images captured from above.