midterm2

Question 1

5 paths

Answer 1

1 sun to target to sensor
2sun to sky to sensor
3sun to sky to earth to sensor
4 sun earth (not target) to sensor
5 sun to earth (not target) to target to sensor

Question 2

advantage of remote sensing as regards sampling methods

Answer 2

can remove sampling bias

Question 3

4 step remote sensing process

Answer 3

statement of problem–data collection–data to info conversion–info presentation

Question 4

examples of collateral data

Answer 4

digital elevation models, soil maps, surficial geology maps, population density, etc.

Question 5

limitations of remote sensing

Answer 5

human method-produced error, cost

Question 6

factors affecting what is sensed

Answer 6

-wavelength,
-location and size of picture element,
temporal info
-set of angles
-polarization of back-scattered energy
-radiometric resolution (precision)

Question 7

columns

Answer 7

j, x-axis (vertical)

Question 8

rows

Answer 8

i, y-axis (horizontal)

Question 9

types of remote sensing systems (name 4)

Answer 9

• linear array “pushbroom”
• linear array “whiskbroom” (uses rotating mirror)
• hyperspectral area array (using dispersing element)
• digital frame camera

Question 10

pros and cons of linear array “pushbroom”

Answer 10

each individual sensor has more time to collect light, but because there are a line of sensors being used, each sensor may be recording data differently.

Question 11

pros and cons of linear array “whiskbroom”

Answer 11

pro: information is consistant because only one sensor is used for every pixel. con: lots of moving parts that can wear out

Question 12

type of array used by hyperspectral sensors

Answer 12

pushbroom (row of sensors, moved only by flight path)

Question 13

2 graphical interfaces for digital image processing

Answer 13

ERDAS (ENVI, ER Mapper)

ERSI (ArcGIS)

Question 14

image equalization

Answer 14

spreads out the most frequent intensity values in order to increase the global contrast

Question 15

linear stretching

Answer 15

In any satellite image, the possible pixel values are in the range of 0 to 255. In practice however, not all these values will occur in your images. Suppose you have a certain image in which the values range from 55 to 103. When this map is stretched linearly to output range 0 to 255: the minimum input value 55 is brought to output value 0, and maximum input value 103 is brought to output value 255, and all other values in between change accordingly (using the same formula). As 0 is by default displayed in black, and 255 in white, the contrast will be better when the image is displayed.

Question 16

if you took the same image and doubled the number of rows and columns you would ___ the size on disk

Answer 16

quadrouple

Question 17

BIL

Answer 17

stores entire line together. For example, given a three-band image, all three bands of data are written for row one, all three bands of data are written for row two, and so on. The BIL encoding is a compromise format, allowing fairly easy access to both spatial and spectral information. The BIL data organization can handle any number of bands, and thus accommodates black and white, grayscale, pseudocolor, true color, and multi-spectral image data.

Question 18

BSQ

Answer 18

all the information from each band stored together

Question 19

BIP

Answer 19

Images stored in BIP format have the first pixel for all bands in sequential order, followed by the second pixel for all bands, followed by the third pixel for all bands, etc., interleaved up to the number of pixels.

Question 20

variance

Answer 20

average of the squared differences from the mean

Question 21

IHS

Answer 21

The vertical axis represents intensity (I) which varies from black (0) to white (255) and is not associated with any color. The circumference of the sphere represents hue (H), which is the dominant wavelength of color. Hue values begin with 0 at the midpoint of red tones and increase counterclockwise around the circumference of the sphere to conclude with 255 adjacent to 0. Saturation (S) represents the purity of the color and ranges from 0 at the center of the color sphere to 255 at the circumference. A saturation of 0 represents a completely impure color in which all wavelengths are equally represented and which the eye will perceive as a shade of gray that ranges from white to black depending on intensity.

Question 22

chromaticity color coordinate system

Answer 22

The coordinates in the chromaticity diagram represent the relative fractions of each of the primary colors (red, green, and blue) present in a given color. Since the sum of all three primaries must add to 1, we have the relationship: R + B + B = 1 or B = 1 - (R + G). only x and y are needed to specify coordinates of a color.

Question 23

line drop-outs

Answer 23

an entire line records 0s. This can be corrected with artifical pixels that represent averages of surrounding pixel values

Question 24

line stripping

Answer 24

this happen when a scan line appears uncharacteristically dark or bright because of calibration error.

Question 25

tangential scale distortion is ______ the higher the remote sensing platform (i.e. airplane versus satellite)

Answer 25

minimized

Question 26

intensity interpolation in resamples

Answer 26

cubic convolution smooths the image. nearest neighbor keeps original values better.