What is the difference between an aerial photograph and an orthophoto

For example, in an aerial photo a photographer can make skyscrapers look tall, but in an orthophoto map, they all look the same size -- you just see the building's roof from directly above.

When a cartographer creates an orthophoto map, through the use of photo manipulation programs, he removes the effects of camera or plane tilt and terrain relief from the map. Both these items distort the map's scale. By removing these effects, he creates a map that has uniform scale; that is, he creates a map that happens to look like an aerial photo. Like other maps, the end user can measure directly from the orthophoto without having to correct for distortion. Unlike an aerial photo, a cartographer can overlay additional information on an orthophoto map.

She can use the orthophoto as a source or background image in a geographic information system GIS or use it to review, revise or to collect more information on another map.

By integrating all of the triangles over the domain, a surface is created. Additional elevation data such as spot elevations at summits and depressions and break lines are also collected for the TIN model.

Break lines represent significant terrain features like a lake or cliff that cause a change in slope. TIN triangles do not cross break lines. One reason the TIN model is used is that it requires a much smaller number of points than a gridded DTM does in order to represent the surface terrain with equal accuracy. Orthophoto Rectification Conventional aerial photographs have limited use in GIS because they are not true to scale.

When you look at the center of an aerial photograph, your view is the same as if you were looking straight down from the aircraft. But as you look toward the edges of the photograph, the view of the ground is no longer straight down, but from an angle.

This is called a central perspective projection; scale is true at the very center of the aerial photograph, but not elsewhere. In order to create a scale correct photograph that can be accurately measured, an orthographic projection is necessary, in which the view is straight down over every point in the photograph.

The TIN surface is used to orthogonally rectify the scanned image file. By combining the two data sources, each image pixel has a known position and intensity value. Submit Comment. Your e-mail. Geavis Clients Contact. Geavis is one of the first in Slovenia with the CAA certificate of expertise in the rules of flying unmanned aircraft systems. The Pix4D innovation: an improved accuracy for rolling shutter cameras.

The difference between an aerial photo and a digital orthophoto. GEOSPACE Geospace is Geavis' collection of domestic and foreign web contents describing the adventures of those small civil unmanned drones, the application aspects of aerial photography and geospatial challenges for the benefit of life and business. View my Flipboard Magazine. You can unsubscribe any time.