georeferenssistä

Georeferenssi, known also as georeferencing or georectification, is the process of establishing a spatial reference system for data. It involves associating geographic coordinates with features in a dataset, allowing them to be accurately located and analyzed on a map. This process is crucial for integrating different types of geospatial information and for performing spatial analysis.

The core of georeferencing lies in defining the relationship between the coordinates in a source dataset and a known geographic coordinate system. For raster data, such as scanned maps or aerial photographs, this typically involves identifying a set of ground control points (GCPs) – recognizable features that appear in both the source image and a reference map or satellite imagery. By associating the pixel coordinates of these GCPs with their corresponding real-world coordinates, a transformation can be calculated to warp the source data into the desired coordinate system.

For vector data, georeferencing often involves assigning attribute information that includes spatial coordinates or is linked to a spatial database that manages coordinate data. This ensures that points, lines, and polygons can be precisely placed on a map. Without proper georeferencing, spatial data would lack a defined location, rendering it unusable for mapping, navigation, or geographic analysis. The accuracy of georeferencing depends on the quality of the source data, the number and distribution of control points, and the chosen transformation method.