5 Remote Sensing and Imagery Free Online FlashCards

What is remote sensing?

Remote sensing collects information about a place or object without direct physical contact, using sensors that measure energy reflected or emitted by Earth.

What do passive sensors measure?

Passive sensors measure naturally available energy, usually sunlight reflected from Earth or heat emitted by its surface.

What is a spectral signature?

A spectral signature is a surface’s pattern of reflection or emission across wavelengths.

How is a raster image organized?

A raster is a grid of rows and columns. Each pixel represents a ground area and stores a measured or calculated value.

What values does a digital elevation model store?

A digital elevation model (DEM) is a raster whose cells contain elevation values.

What does spatial resolution describe?

Spatial resolution is the ground area represented by a pixel. A 10-meter pixel represents a smaller area and can show finer features than a 30-meter pixel.

How are bands assigned in a true-color composite?

A true-color composite assigns visible red, green, and blue bands to their corresponding display colors, approximating human vision.

How should image clues be used to identify a feature?

Use clues such as tone, texture, pattern, shape, size, and context together. They support interpretation but do not prove an identification; compare with other dates, reference data, or field observations when reliability matters.

How is NDVI calculated, and what contrast does it emphasize?

NDVI is calculated as $\frac{\text{NIR} - \text{Red}}{\text{NIR} + \text{Red}}$. It emphasizes the contrast between vegetation’s typically strong near-infrared reflectance and red-light absorption.

How do active sensors collect measurements?

Active sensors send out energy and measure its return. Radar sends microwave pulses; lidar sends laser pulses.

What does spectral resolution describe?

Spectral resolution describes which wavelengths are measured and how finely they are divided into bands. More or narrower bands can help distinguish materials.

What does radiometric resolution describe?

Radiometric resolution is a sensor’s ability to record differences in energy. Greater radiometric resolution can represent smaller signal differences, but does not guarantee greater accuracy.