remote sensing exam 1

passive remote sensing

solar backscatter

thermal expansion from earth

collects radiation rather than emitting it to bounce off

active remote sensing

measures radiation by sending some of its own out

solar backscatter

sunlight travels towards earth

interacts with earths surface

some radiation is reflected back

satalite measures the reflected

thermal emission

objects on earth emit thermal radiation

satalite detects

radar and

lidar

radar - sends out microwave radiaiton and measures returned signal

lidar - sends laser pulses and measures return

stages of radiaiton traveling from sun to earth

sun emits

travels through the vaccum

interaction with earths atmosphere

interacts with earths surface

interacts with atmosphere again

collection by a deterctor

electromagnetic specturm

what are the major regions of the electromagnetic spectrum from short wave to long wave

starting short

gamma rays

x rays

UV

visible

infared

microwaves

radio waves

long

electromagentic radiation conductions

energy transfer through direct colisions with particles

heat moving through metal rod

convections

energy moving through physical like liquid

warm air rising

convection cells

electromagnetic wave model two fields

electric field

magnetic field

two properties of electromagnetic waves

wavelength, frequency

key micron lengths

.7- 1 NIR

SWIR 1-3

thermal around 10

plancks law

describes distrubution of emitted radiation across wavelenghts

weins displacement law

identifies the wavelength that a black body emits the most radiation

its wavelength at maximum emission = weins displacement constant/ absolute temperature in K

radiation budget equation

incident radiation = reflected+ absorbed +transmitted

visible light is what micrometers

.4-.7

plancks

assesses wavelength as a function of temperature and wavelength

weins

assesses wavelength

the stephan boltzman law

hotter object is more energy it emits

tells us that a relatively small increase in temp will largely increase energy through radiation output

irradence

radiation arriving at a surface per unit area

exitance

radiation leaving a surface per unit area

radiance

particular radiant flux leaving an area in a direction

solid angle

describes how much field of view an object occupies from a particular viewing positions

every pixel has

spatial location

brightness value

one or more spectural measurments

radiation budget equation

total amount of radiant flux incident to terrain is = to

sum of reflected + absorbed + tramsitted

hemisphereical

the idea that the radiation being reflected could go in any given direction. assumes you measure values from all given directinos

spectral bands

a range of wavelengths measured by a sensor channel

contrast enhancement

expands range of displayed brightness

pseudo color imagry

assign colors to numerical values, dont have ot be accurate represenations of colo

color composites

uses 3 bands to assign blue red and green

approximates what human eye would see

absorption

photon is removed from flux

scattering

photons change direciton

some of the variables that influence the scatter or absporion

wavelength

size

abundance

path length

rayleigh scattering

happens when particles are much smaller than wavelength of radiaiton

intensity of this scattering is strongly inversely proportional to

accounts for blue light scattering more strongly than red, making the sky appear very blue

can cause the need for correction if overly blue

mie scattering

happens when particles are about the same size

could be dust or smoke

think of haze or smoke

can reduce contrast of imagrey

non selective scattering

when particles are much larger than wavelength of visible light

clouds

snow

all visible colors scattered

absorption

molecular properties

abundance

wavelength

path length

when can abspotion occur

when energy of the photon matches energy difference between two allowed states

energy of a molecule is governed by…

electronic state - positions of electrons around nucleus

vibrational state - energy of stretching between atoms

rotational state - energy of rotations around molecules center

translational kinetic energy - determined by speed of motion

absorption +scattering is called

extinction

specular reflectance

radiation reflected off a smooth surface relative to wavelength of light

redirection of all or almost all incident radiation in a single direction

so angle of incidence = angle of reflection

diffuse reflectance

radiation reflected off a rough surface

redirection incident in many directions

what if reflectance occurs equally in all directions in diffuse reflectance

called lambertian reflectance

spectral signatures

more is better

chloryphyll a and b

absorb blue and red so green is reflected

as the number of healthy leaves increases

NIR reflectance measured by remote sensor increases

red edge

big increase of reflectance near red and infared

distinctive in healthy vegetation

vegetation water content

short wave IR shows changes in reflectance from water content

healthy vegetation

has high NIR reflectance and low red reflectance

simple ratio

compares NIR and red reflectances

helps distiguish vegetation from non vegetation

NDVI

healthy vegetation reflect strongly in NIR and absorbs red

shows vegetation signal

optical system

collects and focuses radiiaiton on earths scene

wavelength and seperation system

seperates wavelength into specific ranges

detector

measrues radiation and convets it into what can be used as digital values

whisk broom scanners

scan across direction of scanners

pushbroom scanners

they use linear array detectors to collect measruements as the satallites move forward

resolution

AVHRR

satallite sensor used to monitor vegitation

takes big spaces

can observe in a day

chloroplasts containing chloryphyll

reflects green

spongey mesophyll reflects

NIR