A vertical aerial photograph contains several anomalies as a result of elevation differences in the terrain, lens distortion and the position of the airplane. A digital orthophotograph is an aerial photograph in which all of these anomalies have been corrected. It is a digital photographic map.

The quality of a digital orthophotograph consists of two parts; the image quality and the Geometric accuracy. The most important variables are flight scale, pixel resolution, overlap, survey pre-marks, elevation model and triangulation process. Both the unit of measurement chosen and the equipment used have considerable impact on the end product. With the advent of increasingly fast computers and high quality software, orthophotographs have continued to gain speed and quality.

The photographs are fitted into a coordinate system using GPS/INS and Aero triangulation and block smoothing. The process is based on the use of survey pre-marks. A number of the pre-marks are part of a calibration area to which the GPS/INS system will be calibrated. A digital elevation model is used for the elevation correction.

- Soil condition

- Vegetation

- Rain water drainage

- Garbage dump

- City and zoning plans

- Housing improvement schemes and    - land parcelling plans

- Traffic planning

- Railway planning

- Public hearings

- Expositions

- Presentations

- Trade shows

- Information meetings

- Meetings

- New housing estates

- Illegal construction

- Parking facilities

- Land transactions

- Tracing out infrastructure

The following image is an example of an orthophotograph..