Digital Orthophotos

---

Higher-resolution image (764,391 bytes)

---

What is the difference between an aerial photograph and an orthophoto?

1. A conventional perspective aerial photograph contains image displacements caused by the tilting of the camera and terrain relief (topography). It does not have a uniform scale. You cannot measure distances on an aerial photograph like you can on a map. It is not a map.
2. The effects of tilt and relief are removed from the aerial photograph by the rectification process to create an orthophoto.
3. An orthophoto is a uniform-scale photograph. It is a photographic map.
4. Since an orthophoto has a uniform scale, it is possible to measure directly on it like other maps.
5. An orthophoto may serve as a base map onto which other map information may be overlaid.