Rem Sen

Front 1

Define passive sensor

Back 1

A sensor capable of only receiving energy emitted or reflected by an external source (e.g. solar energy).

Front 2

Example of a passive sensor:

Back 2

- A regular camera without the flash
- Most satellites are passive remote sensors
(Quick-Bird, Landsat, SPOT, etc...)

Front 3

Define active sensor

Back 3

A sensor which emits it's own energy and uses the reflectance of that energy to interpret data.

Front 4

Example of an active sensor

Back 4

- A camera with the flash turned on.
- LiDAR satellites

Front 5

Name one scientific application of the following satellite sensors:

- QuickBird
- MERIS
- PROBA-CHRIS
- AVHRR
- SeaWiFS
- Landsat TM

Back 5

QuickBird : Crop monitoring
MERIS : Storm tracking
PROBA-CHRIS : Environmental monitoring
AVHRR : Sea surface temperature
SeaWiFS :Concentration of chrolophyll / plankton Landsat
TM: Forest change

Front 6

What can measuring ocean colour with satellites help us to determine? (3 things)

Back 6

Chlorophyll content, temperature, amount of suspended sediments

Front 7

What can the concentration of phytoplankton in our oceans tell us? (3 things)

Back 7

The concentration and distribution of phytoplankton has significant implications on
- fish distribution
- marine ecosystem health
- climate change

Front 8

A single remote sensing platform (satellite) can have a variety of scanners. Provide 1 example of this.

Back 8

Landsat has a thematic mapper and
multi-spectral scanning system

Front 9

When EMR first enters the atmosphere it is

susceptible to: (3 things)

Back 9

- Transmission
- Absorbtion
- Scattering

Front 10

Define the main concepts of the following
resolutions:

- Spatial resolution:
- Spectral resolution:
- Radiometric resolution:
- Temporal resolution:

Back 10

- Spatial – Pixel size, area of ground covered

- Spectral – (How many bands and range of wavelengths)

- Radiometric – Visual acuity of captured image, 8-bit (“Bits” per “band”)

- Temporal – Frequency of re-imaging same area (How often does it come back?)

Front 11

Broad definition of "resolution" :

Back 11

The ability to see an object with a certain level of clarity

Front 12

There is a key difference between thermal scanners and other passive sensors, what is it?

Back 12

Thermal scanners detect radiation that is emitted not reflected from objects.
The objects’ temperature and physical
composition will determine the amount of
radiation it gives off

Front 13

If everything emits some amount of heat (energy), how do we prevent thermal scanners from producing their own heat which could interfere with received energy?

Back 13

If we can cool the sensor enough, its own emissions won’t interfere with the received energy. Current thermal scanners can detect temperature differences of 0.1°C for objects on the ground. This means that the sensor would have to be cooled to 77°K using a liquid nitrogen “thermos”.

Front 14

Applications of thermal scanners

Back 14

- Thermal scanners can be used to interpret and predict weather patterns

- definitely more but im done

Front 15

Two main methods by which reflected EMR is gathered by a satellite sensor :

How do they work?

Back 15

Across- track : uses rotating mirror that sweeps across the field of view to image the earth.

Along - track : uses a longer CCD (Charge Coupled Device) array to pick up EMR one line or row at a time.

Front 16

Main differences between Across - track (mirrors) and Along - track (longer CCD)

Back 16

Across-track scanners have much fewer

detectors to calibrate and mirrors are more reliable than thermal detectors.

Along-track scanner is simpler, has fewer moving parts, requires less energy, there is a lower potential for pixel distortion, IFoV dwell times are longer which = better spatial and radiometric resolution.

Front 17

Relationship between spatial and radiometric resolution:

Back 17

Shorter dwell times will result in the need for a larger CCD to accommodate for the low radiometric resolution, but this in turn lowers the spatial resolution.

Longer dwell times will allow you to maintain both a high radiometric resolution, and a high spatial resolution by using a smaller CCD.

Front 18

Spatial resolution

Back 18

Spatial resolution is a measure of the smallest object that can be resolved or distinguished by a sensor CCD.

It is a combination of;- the area imaged by the sensor in one “glance”(Instantaneous Field of View or IFoV) and;- the height of the sensor above the earth or other object-

Ground resolution = IFoV x height above earth.

Front 19

Radiometric resolution

Back 19

Radiometric resolution is the sensitivity of a sensor to slight changes in EMR energy and thus reflectance assigned to each pixel.

Recall that each pixel can only be assigned one value and so the range of possible values that can be assigned is the radiometric resolution.

256 values = 8bit radiometric resolution

Front 20

Temporal Resolution

Back 20

Temporal resolution is the time that it takes for a satellite to complete one orbital cycle and image the same geographical again

Front 21

Spectral resolution

Back 21

- Spectral resolution refers to the range of wavelengths of EMR that a sensor can detect.

- EMR wavelengths range from 10m(Gamma rays) all the way to 10^(-12)m (radio waves).

- Wavelengths used in passive remote sensing range from 0.0000001m (0.1µm, Ultraviolet) up to 1.0m(microwave).

Front 22

What is IFoV?

Back 22

(Instantaneous Field of View)

the area imaged by the sensor in one “glance”

Front 23

Human eyes are sensitive to what spectral range?

Back 23

from 0.4µm (violet) to 0.7µm (red).

Front 24

What do Bands 1, 2 , and 3 correspond to?
(Which 3 colours)

What is significant about these 3 colours?

Back 24

Band 1 = blue
Band 2 = green
Band 3 = red

RGB is significant because we can create any colour by using a combination of these 3.

Front 25

More on spectral resolution:

Back 25

- Different areas or objects on the Earth’s surface interact with the energy in these spectral bands indifferent ways.

- This difference in energy interaction allows us to distinguish between areas of water, forest, urban,and grass land use/covers among others.

- The spectral signature for forest is quite different from water in some of the spectral bands allowing us to differentiate between them on the image.

Front 26

- Sensors can be ______________ (several bands)
or ______________ (hundreds of narrow bands).

Back 26

multi-spectral , hyperspectral

Front 27

In regards to temporal resolution, what does geo-synchronous mean?

Back 27

a satellite that orbits in such a way that it is
always over the same spot

Front 28

EMR waves are composed of what?

Back 28

EMR waves are composed of energy particles called photons or quanta

Front 29

With slight increases in temperature, what happens to the total energy emitted by an
object?

Back 29

The total energy emitted by an object increases to the power of 4.

Front 30

EMR interacts with particles and gases in the atmosphere through two principal mechanisms:

Back 30

scattering and absorption

Front 31

The degree of scattering depends on a number offactors including: (3 things)

Back 31

- wavelength of radiation

- density of particles or gases

- the path length

Front 32

3 types of scattering mechanisms:

Back 32

- Rayleigh

- Mie

- Non-selective.

Front 33

Rayleigh Scattering:

Back 33

Caused by the interaction of tiny particles that are smaller in diameter than the wavelength.

Tiny particles preferentially scatter shorterwavelengths (i.e. blue light). (Why the sky is blue)

Front 34

Why is the sky red or orange at sunset?
(Rayleigh Scattering)

Back 34

EMR must travel through a thicker portion of the atmosphere so almost all shorter wavelengths get scattered and only oranges and reds pass through.

Front 35

Mie scattering:

Back 35

Caused by the interaction of particles that areabout the same diameter as the wavelength.
(Dominant scattering mechanism on overcast days)

Dust, pollen, smoke, and water vapour are all causes.

Front 36

Non-selective scattering

Back 36

Caused by the interaction of particles that are much larger than the wavelength. (Large water or dust particles)

another example would be fog, or dust billowing from a gravel road.

Front 37

3 things in the atmosphere that absorb the most EMR:

Back 37

Ozone, carbon dioxide and water vapor