Raster analysis

Question 1

The simplest type of values to display are _

Answer 1

Integers

Question 2

Map algebra is an _ _ for manipulating representations of _ _ defined over a common domain

Answer 2

informal language

continuous variable

Question 3

What are the 4 groups of map algebra functions?

Answer 3

• local or cell-based operations
• focal or cell neighborhood-based operations
• zonal or cell group operations
• global operations

Question 4

in local processing operations, map values for processing are retrieved for a _ map location _ reference to other map locations or extended spatial contexts, then processed and the result stored at the location

Answer 4

single

without

Question 5

Local operations operate on a _ by _ basis

Answer 5

cell by cell

Question 6

T or F- you can multiply soil type 3 and soil type 5 in local operations

Answer 6

F

Question 7

What 3 analysis methods do local operations include?

Answer 7

• reclassification/recoding
• overlay
• scalar (modify cell values by a constant)

Question 8

What are the 4 methods of reclassification?

Answer 8

• assign new value to each unique value on input layer (only works if there arent that many unique inputs)
• assign new values by assigning cells to classes based on their old values (for satellite images/elevation)
• sort the unique values in input layer into rank of value
• assign new values based on mathematical operations

Question 9

What characteristics should the grids share when doing raster overlay?

Answer 9

• geographic extent
• projection
• cell resolution
• sampling interval

Question 10

What are the 3 groups of math operators for map algebra?

Answer 10

• arithmatic
• boolean (AND, NOT, OR) TRUE=1, False=0
• relational (

Question 11

In focal operations a cell’s value in a new layer is determined by the _ of the cells _ it on the input layer

Answer 11

values

surrounding

Question 12

in focal processing operations, map values for processing are retrieved from _ map locations with reference to _, _, _ or other spatial contexts, then processed and the result stored for the location at the /

Answer 12

multiple 
adjacent
neighboring 
proximal 
center/focus

Question 13

what are the 2 focal neighborhood operations

Answer 13

• filtering

- slope and aspect derivation

Question 14

a filter operates by moving a _ across the _ _

Answer 14

window

entire raster

Question 15

What is the mechanism of filtering?

Answer 15

-compute a new value for the cell in the centre of the window based on the weighted values of the cells in the window

Question 16

T or F, low pass filters smooths, reduces local detail, and removes extreme values

Answer 16

T

Question 17

what are the 4 types of low pass filters?

Answer 17

• mean filter
• weighted average
• majority filter
• median filter

Question 18

T or F, mean filter severely smooths the spatial variation on the layer

Answer 18

T

Question 19

T or F, weighted average low pass filter gives the center cell of the window 24 times the weight of its old value and severely smooths the layer

Answer 19

F, 12 times and old value and slightly smooths.

Question 20

T or F, majority filter replaces central value with most frequently occurring value in the window and can be used to generalize nominal image/fill gaps after vector to raster conversion

Answer 20

T

Question 21

_ filter replaces central value with median value in the window and is good for _ _ in poor quality images

Answer 21

median

noise removal

Question 22

High pass filters _ local detail for _ _ and enhances local detail by giving neighbors _ _ if condition is different

Answer 22

exaggerate
edge enhancement
negative weights

Question 23

directional filters are used to enhance or detect _ _ in images, and weights in window are set according to the _ _ that you want to enhance

Answer 23

directional structures

compass direction

Question 24

In zonal processing operations, map values for processing are retrieved for _ map locations within the extent of each _ feature, then processed and the summary result stored for all the locations defining each template

Answer 24

multiple

template

Question 25

what are the 3 applications of zonal operations?

Answer 25

• identifiying zones
• areas of zones
• perimeters of zones

Question 26

Identifying zones works by comparing _ cells, _ all patches having the _ value, then give each such patch a unique #, and set each cell’s value to the _ of its patch

Answer 26

adjacent
identify
same
number

Question 27

T or F areas of zones method measures the area of each zone and assign this value to each cell instead of the zone’s number, area calculated by “# cells x area of each cell”

Answer 27

T

Question 28

T or F, the perimeter of zones measure the radius of each zone and assign this value to each cell, calculated by ‘# exterior cell edges x length of cell edge’

Answer 28

F. the perimeter of zones measure the perimeter of each zone and assign this value to each cell, calculated by ‘# exterior cell edges x resolution of cell’

Question 29

Name the 4 global operations

Answer 29

• distance
• buffer zones
• viewsheds
• least cost pathways (generate a friction surface, create an accumulated cost surface from origin to destination cells, create a least cost path across the accumulated cost surface from origin to destination