tocrs

tocrs refers to the process of converting spatial data coordinates from one coordinate reference system (CRS) to another. In practice, software libraries expose this as a function or method, often named to_crs, which returns geometry data expressed in the target CRS. The operation relies on a transformation pipeline that uses a source CRS, a target CRS, and a defined datum transformation when needed.

How it works: A reproject operation uses mathematical formulas to map coordinates from one CRS to another. It may involve converting from a geographic CRS (latitude/longitude) to a projected CRS (flat map coordinates) and may require datum shifts to align ellipsoids. Modern toolchains rely on libraries such as PROJ to handle the underlying transformations, including axis order, units, and any grid-based corrections. The result is a new dataset whose geometry coordinates are defined in the target CRS, while non-spatial attributes usually remain unchanged.

Usage: The to_crs operation is widely available in GIS software and libraries, including QGIS, PostGIS, GDAL/OGR, PyProj, and GeoPandas. It accepts target CRS definitions in formats such as EPSG codes, PROJ strings, or WKT. In programming environments, it can be applied to entire datasets or individual geometries, enabling on-the-fly or persisted reprojection for analysis and visualization.

Considerations: Reprojection can introduce distortions depending on the source and target CRS. Datum transformations can affect accuracy, especially for areas near tectonic boundaries. It is important to verify units, axis orientation, and validity of the transformed data for the intended analysis.

See also: Coordinate reference system, EPSG, PROJ, GDAL, PyProj, GeoPandas, PostGIS.