Georeferencing
Topic: Remote Sensing, GIS and GNSS · NCERT: Class 12, Ch 4 "Spatial Information Technology"
Meaning
Georeferencing means giving a scanned map, image or dataset real-world coordinates in a fixed coordinate system, such as latitude and longitude. After this, each feature sits at its true place on the earth, and different layers line up correctly on top of one another. Errors here put data at the wrong scale or in the wrong place. Distortion can also come from faults in the camera lens, from relief (the ups and downs of the land) or from folds in a paper map.
Example
A scanned toposheet of Dehradun is just a picture until it is georeferenced. Known points, such as road crossings, are given their real coordinates. Then a satellite image of the same area can be laid over it and the roads match.
Don't confuse with
- Digitisation: digitisation traces features into coordinates. Georeferencing ties the whole map or image to real locations on the earth.
Related concepts
- Raster data model
- Vector data model
- Topology
- Digitisation
- Scanner
- Charge-coupled device
- Raster-vector conversion
- Exact matching
- Hierarchical matching
- Fuzzy matching