Unit 3

Question 1

What’s the difference between analogue and digital photography?

Answer 1

Analogue is a continuously varying quantity and digital is discrete brightness or intensity levels

Question 2

What are the two ways of taking images?

Answer 2

Framing (one point) or Scanning (sensor scans along/across path)

Question 3

What are the benefits of Aerial Photography?

Answer 3

1. It can be cheaper than launching a satellite
2. has a better spatial resolution
3. good for historical imagery

Question 4

How does analogue photography work?

Answer 4

Uses emulsion layers, each layer absorbs a wavelength of EM

Question 5

What are the two devices used for collecting digital imagery?

Answer 5

Using Charged Coupled Devices (CCD) or Complementary Metal-oxide-semiconductors (CMOS)

Each raw image is made of pixels containing digital numbers

Question 6

What is the consequence of digital numbers (DN)

Answer 6

When the photon is received the DN represents the number of them (brightness) and the image can be easily overexposed if you reach max DN

Question 7

How does Landsat-7 relate to across-track scanners?

Answer 7

There are many moving parts and it continuously records information. If one of those parts fails like with Landsat-7 then you lose data.

Question 8

What are the advantages of along-track scanners?

Answer 8

1. Fewer malfunctions from reduced moving parts
2. looks at ground longer = improved radiometric and spectral resolution
3. smaller IFOV improving spatial resolution

Question 9

What are the downsides of along-track scanners?

Answer 9

Many detectors have to be calibrated

Question 10

What are the types of resolution?

Answer 10

spatial, spectral, radiometric, and temporal

Question 11

How is spatial resolution limited?

Answer 11

The smallest distinguishable ground feature in the image is limited by:

1. the # of CCD detectors for the sensors
2. IFOV
3. number and size of crystals in emulsion layers (analogue)

Question 12

What is IFOV

Answer 12

the cone of visibility to the detector

Question 13

How can we use IFOV to increase resolution?

Answer 13

Lower the platform, or decrease the angle

Question 14

How does pan-sharpening increase resolution?

Answer 14

Merges high-resolution pan-chromatic and lower resolution multispectral

Question 15

How is bandwidth related to spectral resolution?

Answer 15

The number of spectral bands and size of them determines the ability to separate entities. Smaller spectral bands have greater resolution.

Question 16

What is BIT depth related to?

Answer 16

Bit depth relates to radiometric resolution as the number of bits determines how sensitive the sensors are to small changes in EM (brightness values)

Question 17

What is a geostationary orbit?

Answer 17

Geostationary orbits are in synchrony with Earth’s orbit above the equator temporal resolution

Question 18

How can we address spatial and temporal resolution trade-offs?

Answer 18

Using constellations of several satellites (tandem orbits)

Question 19

Review the tradeoffs

Answer 19

end of unit 3