Ortorektifiering

Ortorektifiering is a digital image processing technique used to correct geometric distortions in aerial or satellite imagery. These distortions arise from several factors, including the tilt of the sensor relative to the ground, the curvature of the Earth, and variations in terrain elevation. The goal of ortorektifiering is to remove these distortions, creating an orthorectified image that is geometrically accurate and can be used for precise measurements and mapping.

The process typically involves using a digital elevation model (DEM) of the terrain. This DEM provides the elevation data for each point in the image. During ortorektifiering, each pixel in the original image is relocated to its correct geographic position based on its original location, the sensor's position and orientation, and the elevation data from the DEM. Pixels that were stretched or compressed due to terrain variations are adjusted to their true scale and position.

The resulting orthorectified image, also known as an orthophoto, has a uniform scale throughout, similar to a map. This means that distances and areas can be measured directly from the orthophoto with high accuracy. This geometric correction is crucial for applications such as photogrammetry, geographic information systems (GIS), land-use planning, environmental monitoring, and urban development. Without ortorektifiering, aerial and satellite images would not be suitable for precise spatial analysis and mapping.