Nature of an Image

Question 1

digital RS imagery

Answer 1

• array of scene elements “pixels”
• based on raster format
• not a photograph
• a pixel records EMR from Earth as a digital number

Question 2

Image

Answer 2

a rendition of target features described through the use of EMR

Question 3

sensors recording EMR determine ____

Answer 3

resolution

Question 4

Tpes of resolution

Answer 4

• spatial
• spectral
• temporal
• radiometric

Question 5

Pixel location and size:

Answer 5

ground footprint

Question 6

pixel brightness is controlled by:

Answer 6

nature of the target

allows creation of spectral signature

Question 7

levels of pixel brightness determined by:

Answer 7

radiometric resolution (bit depth)

Question 8

types of imaging systems

Answer 8

• frame
• scanner
• whiskbroom
• pushbroom

Question 9

visible light wavelength range

Answer 9

400-700 nm

Question 10

Spectral resolution

Answer 10

number of spectral bands

Question 11

spatial resolution

Answer 11

pixel size or scale

Question 12

temporal resolution

Answer 12

timescale

Question 13

Multispectral Image

Answer 13

image composed of ‘n’ rows and columns of pixels for multiple spectral bands

more than one raster data set or spectral band

Question 14

what is each data set in a multispectral image

Answer 14

a spectral band

Question 15

multispectral images detect ____ in multiple bands of EMR

Answer 15

energy

Question 16

how to display a colour composite with a multispectral image

Answer 16

three bands combine into red, green, and blue

Question 17

Binary Numbers

Answer 17

Bit depth (2^n), represent decimal numbers

.# of bits = # of decimal levels

Question 18

how are digital numbers typically stored

Answer 18

binary form

Question 19

Digital numbers are a type of what kind of resolution and why

Answer 19

radiometric, because the binary number (BIT) is also the amount of grey levels)

Question 20

additive colour

Answer 20

RGB on top of each other create white light, and selectively adding RGB creates YMandC

Question 21

Subtractive colour

Answer 21

YMC superimposed create black, with RGB in the overlap margins

Question 22

true colour composite

Answer 22

RGB guns match RGB bands

Question 23

why digitally process RS data

Answer 23

• capable of more detail and precision than humans
• humaninterpretation is subjective and not always repeatable
• computer can better handle large amounts of data
• can manipulate images with low contrast

Question 24

digital number

Answer 24

numerical digit assigned to a pixel

Question 25

compute image histogram

Answer 25

.# of pixels vs DN selected from a region of an actual image

Question 26

DN in a histogram

Answer 26

brightness value represented as anumber (lowest is darkest)

Question 27

why enhance

Answer 27

Increase contrast

Question 28

histogram analysis

Answer 28

examining distribution of pixel values in an image to understand characteristics

Question 29

linear contrast enhancement

min-max stretch

Answer 29

stretch entire histogram linearly based on min and max values

Question 30

percentage contrast enhancement

saturation stretch

Answer 30

zero in on portion of histogram we are interested in and give whole dynamic range to that part

Question 31

pros and cons of percentage stretch

Answer 31

lose variability above and below threshold but gain max contrast in our section

outside of our threshold the image is black or white, fully saturated

Question 32

image composite interpretation

Answer 32

composite images by combining multiple bands or channels to enhance specific features