Geo 213 Final I Flashcards
The big three?
GPS
GIS
REMOTE SENSING
-acquisition and analysis of image data from aircraft and satellite systems
Remote sensing applications?
Homeland Security Forestry Weather forecasting Urban planning Agriculture
Key areas of development?
Radar
Lidar
UAV
Parts?
Instrument - what is taking the picture
Platform - vehicle upon which instrument is mounted
=aircraft, spacecraft
Active vs. Passive?
Active - emits energy and records reflected energy off of object = “flash”
Passive - does NOT emit energy, uses natural energy (sun) = no “flash”
Extra helps to remote sensing
In-situ data = on the ground
-connect remote sensing data to real world
Ancillary data = maps, reports, etc…
Value of field work
#1 - imagery can be geometrically and radiometrically calibrated #2 - data must be interpreted/analyzed = compared to what is on the ground
What is radiometric calibration?
Converting digital numbers to something physical
=use targets of known reflectance to convert raw data
(atmosphere messes data up)
Advantages to remote sensing?
1) collect data systematically
- through time = compare changes over time
2) unobtrusive, passive
- (privacy a concern)
3) can collect valuable data
- it works! (most of the time)
Limitations to remote sensing?
1) often oversold
- have realistic expectations
2) ACTIVE RS can be intrusive
3) can be expensive to collect, analyze
Five project phases
1) statement of problem
2) data collection
3) preprocessing phase
4) analysis phase
5) present information, solve problem
Types of resolution
Spectral *false color / color infrared : -IR = red -Green = blue -Red = green -Blue = n/a Spatial *how small of an element can I detect on ground? Temporal *how often can I get the overpass of airplane/satellite to collect data?
Spectral resolution
single, multispectral, hyperspectral
- multi = LANDSAT, ASTER
- hyper = AISA
Spatial resolution
Resolution given as pixel size = ground size
i.e. 1m, 20m, etc..
Temporal resolution
shorter generally better - can combine for longer term but cannot subdivide long into small
Advances in RS
- platforms (helicopter,airplane, satellite)
- sensors (cameras)
- data processing + computers
- programs
Future advances
- smaller satellites, fewer sensors
- sensor constellations
- huge satellites w/exhaustive sensor arrays
- single-mission satellites
- specialized sensors
- higher resolution
Sensor families
1) film
2) digital
3) multispectral
4) pushbroom
5) thermal radiometers
6) hyperspectral
7) radar
8) lidar
9) radar altimeters
10) scatterometers
Passive sensors
Target is self-illuminated not by sensor
weather satellites, optical/IR satellites
Active sensors
Target illuminated by energy from sensor
radar, lidar, sonar
EMR
electromagnetic radiation
=produced by vibrating electrical charge
Black body
Absorbs ALL energy that strikes it
=none reflected, transmitted
*DOES re-radiate energy at different wavelength
Wien’s displacement law
As temperature increases, peak emissions shift towards shorter part of EM spectrum
Wavelength Classification
- 3-0.4 micrometers = Near Ultraviolet
- 4-0.5 micrometers = Blue
- 5-0.6 micrometers = Green
- 6-0.7 micrometers = Red
- 7-2.5 micrometers = Near Infrared
Stefan-Boltmann law
Increase temperature, energy increases to FOURTH power
Atmosphere can affect…
wavelength
intensity
spectral distribution
direction
Three types of scattering
Rayleigh
Mie
Non-selective
Rayleigh
diameter of matter is many time SMALLER than wavelength
=responsible for BLUE SKY
(short blue scattered more than red)
Mie
caused by matter ~same size as wavelength
-amount of scatter MORE than Rayleigh & scattered wavelengths are LONGER
=mostly caused by POLLUTION
Non-selective
all wavelengths scattered equally
Types of reflectance
Specular
Diffuse
Lambertian
Specular reflectance
surface is essentially SMOOTH
-reflectance is mirror image
=low return for radar
Diffuse reflectance
surface is ROUGH
-diffused radiation = BACKSCATTER
=this is what returns to radar (GOOD)
Lambertian reflectance
surface so rough, energy is perfectly diffused
-many models make this assumption to help with the math
20s, 30s
9x9 cameras
amazing resolution, quality
can be blown up to 36x36 poster!
1972
first multispectral satellite launched (LANSAT)
first one used for civilian remote sensing
RS phases
Pre-WWII : balloons
WWI-WWII : airplanes
WWII - cold war : satellites
cold war - present : UAV
Air photo terms
- principal point
-geometric center point on photograph - field of view
-angular measurement of how much landscape you can see
high oblique
-can see horizon - low oblique
~45°
Radiometric resolution
amount of bits used to store brightness
8-bit
12-bit
16-bit
