Scanner
Topic: Remote Sensing, GIS and GNSS · NCERT: Class 12, Ch 4 "Spatial Information Technology"
Meaning
A scanner is a device that turns paper maps or documents into high-resolution raster images, which are grids of tiny cells. A light source shines on the sheet. Charge-coupled devices (CCDs), light sensors inside the scanner, change the reflected light into digital values. The scanned map can be used as it is, for example as a backdrop map. Often it is cleaned up or converted into vector form before analysis.
Example
An old paper map of Delhi's land use is scanned to make a digital copy. It is then georeferenced and used as a base layer, and roads and colonies are traced from it.
Don't confuse with
- Multispectral scanner: this is a sensor on a satellite or aircraft that records energy from the earth's surface. A map scanner copies paper maps in an office.
- Digitisation: a scanner makes a raster picture of the whole sheet. Digitisation traces each feature as vector data.
Related concepts
- Raster data model
- Vector data model
- Topology
- Digitisation
- Charge-coupled device
- Georeferencing
- Raster-vector conversion
- Exact matching
- Hierarchical matching
- Fuzzy matching