Pixel
Also called: Picture element · Topic: Remote Sensing, GIS and GNSS · NCERT: Class 11, Ch 6 "Introduction to Remote Sensing"; Class 12, Ch 4 "Spatial Information Technology"
Meaning
A pixel (picture element) is the smallest cell of a digital image or raster grid. Each pixel has a fixed address in rows and columns and holds one value. In a satellite image, that value is a digital number for the average brightness of the ground cell. The ground size of one pixel sets the spatial resolution, so smaller pixels show finer detail. Zoom in too far and you see only squares, not more detail.
Example
Each pixel of the IRS PAN camera covers 5.8 m on the ground. Each pixel of Cartosat-3 (2019) covers about 25 cm, which is fine enough to pick out cars and single buildings in Indian cities.
Don't confuse with
- Digital number (DN): the value stored inside the pixel, not the cell itself.
- Swath: the width of the whole strip imaged in one pass, made up of many pixels side by side.
Related concepts
- Aerial photograph
- Digital image
- Digital number
- Digital image processing
- False colour composite
- Visual image interpretation
- Elements of visual interpretation
- Tone
- Texture
- Shadow in image interpretation