Orthophoto

Part of speech: noun

Definitions

1. A precise aerial photograph that has been geometrically corrected to ensure that scale is uniform across the image
2. A corrected image capturing the Earth's surface as a map, eliminating distortions from perspective
3. A high-resolution ortho-image representing real-world coordinates, commonly used in mapping and GIS applications

Etymology: The word is a modern technical coinage, built from two Greek elements that were never joined in antiquity. "Ortho-" comes from Ancient Greek "orthós", meaning straight, upright or correct, while "photo" is a clipping of "photograph", itself from Greek "phōs" (light) and "graphē" (drawing or writing). Put together, the sense is "correctly drawn light," which fits a process designed to straighten out the distortions in aerial images. The "ortho-" prefix is the more familiar piece in English, appearing in words like "orthodox" (correct belief) and "orthopaedic" (straightening of the body). Here it signals that the picture has been made geometrically true, so that distances measured on it match distances on the ground. An ordinary aerial photograph is distorted by the camera's tilt and by the shape of the terrain, which is why this correction is needed.