The science of making precise measurements and spatial data from photographs. By analysing the geometry of objects as they appear in an image — their relative size, position, and perspective — photogrammetrists can calculate real-world distances, elevations, and coordinates without physically measuring them on the ground. In the context of rephotographyRephotography — sometimes called repeat photography — is the practice of photographing the same location from the same position on two or more separate occasions, with a significant time gap between images. The objective is a direct visual comparison: a diachronic pair that shows what has changed, what has survived, and what has been lost entirely. Read the Post - The Art and Craft of Photographing Time. Rephotography Organisations and Information More, photogrammetric principles underpin the practice of precisely reoccupying an original camera position: working backwards from the geometry of a historical photograph to determine exactly where, at what height, and with what focal lengthThe optical distance in millimetres between a camera lens and the film (or sensor on a digital camera). It determines the height and width of the scene being captured, known as the field of view. More the original image was made.