Raster analysis Flashcards
The simplest type of values to display are _
Integers
Map algebra is an _ _ for manipulating representations of _ _ defined over a common domain
informal language
continuous variable
What are the 4 groups of map algebra functions?
- local or cell-based operations
- focal or cell neighborhood-based operations
- zonal or cell group operations
- global operations
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
single
without
Local operations operate on a _ by _ basis
cell by cell
T or F- you can multiply soil type 3 and soil type 5 in local operations
F
What 3 analysis methods do local operations include?
- reclassification/recoding
- overlay
- scalar (modify cell values by a constant)
What are the 4 methods of reclassification?
- 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
What characteristics should the grids share when doing raster overlay?
- geographic extent
- projection
- cell resolution
- sampling interval
What are the 3 groups of math operators for map algebra?
- arithmatic
- boolean (AND, NOT, OR) TRUE=1, False=0
- relational (
In focal operations a cell’s value in a new layer is determined by the _ of the cells _ it on the input layer
values
surrounding
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 /
multiple adjacent neighboring proximal center/focus
what are the 2 focal neighborhood operations
- filtering
- slope and aspect derivation
a filter operates by moving a _ across the _ _
window
entire raster
What is the mechanism of filtering?
-compute a new value for the cell in the centre of the window based on the weighted values of the cells in the window
T or F, low pass filters smooths, reduces local detail, and removes extreme values
T
what are the 4 types of low pass filters?
- mean filter
- weighted average
- majority filter
- median filter
T or F, mean filter severely smooths the spatial variation on the layer
T
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
F, 12 times and old value and slightly smooths.
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
T
_ filter replaces central value with median value in the window and is good for _ _ in poor quality images
median
noise removal
High pass filters _ local detail for _ _ and enhances local detail by giving neighbors _ _ if condition is different
exaggerate
edge enhancement
negative weights
directional filters are used to enhance or detect _ _ in images, and weights in window are set according to the _ _ that you want to enhance
directional structures
compass direction
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
multiple
template
what are the 3 applications of zonal operations?
- identifiying zones
- areas of zones
- perimeters of zones
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
adjacent
identify
same
number
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”
T
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’
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’
Name the 4 global operations
- 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
