Shadow in image interpretation
Topic: Remote Sensing, GIS and GNSS · NCERT: Class 11, Ch 6 "Introduction to Remote Sensing"
Meaning
Shadow is the dark shape cast by a tall object. Its length depends on the height of the object and the angle of the sun. Seen from above, a tall, thin object shows very little of itself, but its shadow shows its shape and height. Shadow is one of the image characteristics used in visual interpretation. It is more useful in large-scale aerial photographs than in satellite images, where objects and shadows are often too small to see clearly.
Example
On an aerial photograph of Delhi, the Qutub Minar looks like a small dot from directly above. Its long shadow on the ground shows that it is a tall tower. Overhead water tanks are identified in the same way.
Don't confuse with
- Tone: the brightness or colour of the object's own surface, which depends on how much energy it reflects. Shadow is the dark area its height throws onto the ground.
Related concepts
- Aerial photograph
- Digital image
- Pixel
- Digital number
- Digital image processing
- False colour composite
- Visual image interpretation
- Elements of visual interpretation
- Tone
- Texture