# 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)