When you ortho-rectify a raster dataset, you are given a choice whether or not to use Geoid correction. Geoid correction should be applied when your data source is using orthometric heights and you want to perform a geoid (EGM96) correction to the z-values. Orthometric heights are measured near sea level – which tends to be the case in many images.
Orthorectification can be performed various ways within ArcGIS:
- Geoprocessing – Create Ortho Corrected Raster Dataset tool
- Image Analysis window – Orthorectify button
- Geomtric Function
- Layer Properties Display tab