Active vs. Passive Sensors
Active - emits energy to measure the reflected signal
Passive - uses natural sourcing to measure
Optical and infrared imagers
Uses visible light and special properties of photons - used for images of organs, tissues, and cells
Radiometers
Measures radiant energy
LIDAR (Light detection & ranging)
uses laser pulses to measure distances and create accurate 3D models
Active vs Passive Sensors
Active - emits energy to measure the reflected signal
Passive - detects natural emitting energy
Optical and infrared imagers
Uses visible light and properties of photons to create detailed images - organs, tissues, and cells
Radiometers
measures radiant energy, measures the intensity and/or energy associated with light of specific wavelengths and if a light-curing system is providing intensity above the minimum or “bulb change” intensity
LIDAR (light detection & ranging)
uses laser pulses to measure distances by measuring the time it takes for the pulses to reflect and create highly accurate 3D models
space-based gravimetry
uses satellites to measure Earth’s gravitational field which is affected by mass distribution
Radar Altimetry
measures the height of a surface by timing how long it takes for a radar pulse to travel from a satellite/aircraft to the surface and back
Precipitation Radar
Used to locate precipitation, calculate its motion, and estimate its type; pulse Doppler radars
Doppler radar
ground/satellite based - uses the Doppler effect to measure wind and precipitation
ground penetrating - uses radar waves to image whats beneath the ground
airborne - uses the Doppler effect to measure the motion of precipitation and air
Reflection
atmosphere - redirection of solar radiation back to space by particles and surfaces in the atmosphere
aerosols - scatter and reflect sunlight back into space
water - light bounces off surface at same angle it hits to create images similar to mirrors
vegetation - reflects green light but absorbs red and blue light
Refraction
atmosphere - bending of light as it passes through Earth’s atmosphere
aerosols - bending of light as it passes through tiny solid/liquid particles suspended in air
water - bending of light as it passes through one medium to another
vegetation - light bending through plant tissue and air space to affect how they see their environment
Attenuation
atmosphere - reduction of signal intensity as it travels through the atmosphere
aerosols - reduction of signal as it passes through suspended particles
water - reduction in light as it travels through water
vegetation - reduction in signal intensity as it travels through vegetation canopies
Transmission
atmosphere - process in which electromagnetic radiation passes through Earth’s atmosphere
aerosols - amount of light which passes through an aerosol cloud used to determine aerosol properties
water - how electromagnetic radiation travels through/scattered/absorbed by water
vegetation - electromagnetic waves through the canopy to measure properties of soil
Scattering of light
atmosphere -
aerosols -
water -
vegetation -
