Lecture 7: Raster data analysis
Values in a raster can be:
continuous (elevation), discrete (landcover), absolute (temperature), coded (suitability classes)
which raster analysis types are there?
local, focal, zonal and global
What is the first step in applying Boolean operators?
reclassification
What is a focal operation?
it involves a focal cell and a set of surrounding cells. The surrounding cells are chosen for their distance and/or directional relationship to the focal cell
What are the four common neighborhood types?
rectangle, circle, annulus and wedge
What is a filter operation?
individual cell values are changed on the basis of neighbouring cell values
Why apply filter operations?
to smooth continuous surfaces/remove speckle/estimate form parameters/enhance changes
How do you get the slope?
it is usually estimated by the use of a filter operation
What is Aspect?
the direction of slope in degrees
What is a zonal operation?
it uses a group of cells defining a geographical area, a zone. they may be contiguous or non contiguous
What does a zonal operation measure?
It measures the geometry of each zone in the raster, such as area
What is the output of global functions?
the value for each cell in the output raster is potentially a function of all the cells combined from the various input raster datasets
True distance =
cell units x cell size
Distance in cell units =
sqrt((x)^2+(y)^2)