georefererend

Georefererend is a Dutch term used to describe the process of georeferencing, the assignment of geographic coordinates to data so that it can be placed in a known coordinate reference system (CRS) and analyzed spatially. It is most commonly applied to raster data such as scanned maps, aerial imagery, or drone orthophotos that do not contain explicit spatial references. By georeferencing, the dataset is tied to real-world locations, enabling integration with other spatial layers and GIS analysis.

The typical workflow includes selecting a target CRS, identifying control points that can be precisely located in both the image and the reference dataset, and computing a mathematical transformation that maps image coordinates to geographic coordinates. Common transformation types include affine, projective, and higher-order polynomial models. The transformation is then applied to the image to produce a georeferenced raster, and the accuracy is assessed using metrics such as the root-mean-square error of the ground control points.

Georeferencing is essential for digitizing historical maps, aligning satellite or drone imagery with basemaps, and compiling multi-source datasets for analysis. The quality depends on the number, distribution, and accuracy of control points, as well as on distortions present in the source material. Data must also be accompanied by metadata describing the CRS, the transformation used, and the date and method of acquisition.

Tools commonly used include GIS software like QGIS and ArcGIS, as well as libraries such as GDAL that provide commands for georeferencing (for example, gdalwarp). Georefererend thus connects non-spatial or poorly located imagery to a precise spatial framework for reliable mapping and analysis.