Remote Sensing

Question 1

what are satelits used for?

Answer 1

• communications - fixed and mobile radio broadcasting
• navigation - GPS
• Earth observation / remote sensing of the physical and human environment

Question 2

what is the history of remote sensing? when was first satellite and when did there become 2000 in orbit?

Answer 2

1950s - first satellite launched
1960s early weather satellites
1972 - first landsat launched 
1990s - first active radar systems
2016 - over 200 satellites now in orbit

Question 3

when did analogue go to digital? what was the resolution?

Answer 3

Landsat series, 1970s

80-15m resoloution

Question 4

what was the analogue film size and resolution?

Answer 4

70mm film

40-5ft resolution

Question 5

what is a geostationary satellite?

Answer 5

An image every 30 minutes or more often, from an altitude of 35,000 km. at this altitude, the speed of rotation is just as fast as the Earth so stays above the same place on earths surface.

Question 6

whats a polar orbiting satellite?

Answer 6

• satellite passes over both poles and can view the whole of the earths surface in a day.
• an altitude of ~800
  km
• orbital period around 100 minutes
• ## sun synchronous so always as light.

Question 7

whats resolution?

Answer 7

the ability of a system to separate a scene into its constituent parts

Question 8

whats spatial resolution?

Answer 8

size of smallest individual component

of an image in surface measurement units

Question 9

whats temporal resolution?

Answer 9

time separation
between repeat
images. Also called
revisit period.
Latitude dependent
for a polar orbiting
satellite

Question 10

whats spectral resolution?

Answer 10

the ability to separate between wavelength intervals

Question 11

electromagnetic spectrum -

whats ultra-violet, visible radiation and thermal radiation?

Answer 11

ultra-violet (short) - information about atmospheric constituents

visible radiation (medium) - information about atmospheric and surface properties

thermal radiation (long) - information about temperature

Question 12

satellite and instruments - whats passive and active?

Answer 12

passive = detects reflected solar radiation or radiation emitted by the earth 
active = provides own source of illumination - radar / Lidar

Question 13

how can satellites measure glaciers?

Answer 13

• monitoring change in glacier extent (optical and Radar)
• measuring flow speed
• measuring surface elevation
• detecting surface melt

Question 14

how do you measure surface elevation?

Answer 14

stereoscopic imaging, radar altimetry, radar interferometry

Question 15

Pros of remote sensing -

Answer 15

• Spatial coverage (Global, increasingly high resolution)
• Repeat observation frequency
• Easy access to data
• Huge archive of data
• Variety of derived products (NDVI, albedo, windspeed)

Question 16

Cons of remote sensing -

Answer 16

-Trade off between spatial and temporal resolution
(Polar orbiting v geostationary)
- Large amount of data to handle
- Data format can be challenging
- Length of time series (may not be as long as in-situ observations)
- Continuity of observations (instrument failure or mission lifetime)