The view from above

Radiation:

• Remote sensing relies on electromagnetic radiation
• an e-m wave is characterised by amplitude, frequency and wavelength
• The waves travel at the speed of light
• amplitude affects brightness and wavelength affects temperature

Active sensors 

• generate waves themselves
• radar/laser

Passive sensors

• natural light is used
• Optical satellite imagery
• sunrays

How an object defers waves is dependent on its optical properties

Different compounds and elements present in nature reflect different parts of the e-m spectrum

Sensors = record the data 

Platforms = hold the sensor

Spatial

• level of spatial detail
• Raster images
• high resolution means there is more detail but it is in a larger file

Spectral

• precision to which a sensor can identify the wavelength of radiaiton
• Low = only three colours
• Lansat bands - different parts of data from the satellite 
• multispectral = multiple bands

Radiometric

• Greyscale
• amount of energy and radiation it recieves 
• high = distinguishes between loads of energy levels
• 8 bit colour is the one used

Temporal 

• frequency the data is colleccted at
• revisited time
• depends on orbital height and path

Field of view

• the angle the satellite hits the earth measured in radians

Swath width

• the area of the earth the satellite sees with angle and height influencing it

Across track seperation

• the overlap between satellites

False colour images

• three bands of images

Elevation data

• we know the speed so measure the time the wavelength comes back to work out distance

1972

Landsat 8 in 2013

Each different sensor looks at a different landsat band

Aerial photography

Flase colour images can show mining 

Unmanned

Airborne laser scanning

• Mounted
• Laser emitted out and measure the time it takes to comne back
• Monitor vegetation
• It can map out the trees on the ground and detect leaves on the floor showing a changing distance therefore season

On the ground

Uses a digital camera

• the more pixels there are the more detailed it will be

Terrestrial laser scanning

• Map out the coastline to track the erosion of the cliffs

To determine change

Atmospheric remote sensing

Air quality

• track what are human emissions and what are sourced naturally

Biogeography

• water depth and grain size
• partial image velocity 
  • velocity = displacement/time between images taken