Lecture 5: Rasters and Map Overlay

Flashcards based on lecture notes about raster data, formats, and operations for GIS. Suitable for review and exam preparation.

What type of data is the land cover data?

Raster data

What is the main characteristic of raster data?

It divides the world into grid cells, each with a value.

What information is required to define a raster dataset?

The bottom left-hand corner coordinates and the size of the grid cells.

What are the two main types of raster data?

Categorical and continuous data.

Give an example of categorical raster data.

Land cover data.

Give an example of continuous raster data.

Elevation data.

Do rasters with continuous data typically have an attribute table?

No, because each cell tends to have a unique value.

When do raster datasets have a value attribute table (VAT)?

When they contain categorical data with shared cell values.

Name a European scale land cover dataset.

Corine data.

Name a National scale land cover dataset.

CH data.

What are the two main LiDAR data products?

Digital Surface Model (DSM) and Digital Terrain Model (DTM).

What does the Digital Surface Model (DSM) represent?

The landscape with features on top, such as buildings and trees.

What does the Digital Terrain Model (DTM) represent?

A bare earth model of the terrain itself.

How can you calculate the height of buildings and vegetation using LiDAR data?

Subtract the DTM from the DSM.

What happens when a raster cell has 'no data'?

It remains a hole in the dataset, and any operation will preserve this 'no data' value.

What is the impact of cell size on raster data?

It affects the level of detail, with smaller cells providing more detail.

What is the general principle when choosing a resolution?

Small areas benefit from high resolution, while large areas can use coarser resolution.

What does 'Raster is faster, but vector just seems more correcter' mean?

Raster operations are fast, but vector data provides cleaner shapes.

How can you combine raster inputs with different resolutions?

By defining the resolution of the output grid.

How can you limit processing to a specific area within a raster?

By using environment settings to define a window or an analysis mask.

What is reclassification in raster analysis?

Changing the values of pixels in a raster based on a defined criteria.

What is a local raster function?

An operation where each pixel is transformed independently, without considering its neighbors.

What is a raster calculator used for?

Applying mathematical functions to raster layers.

What is a focal raster function?

An operation where the value of a pixel is calculated based on the values of its neighboring cells.

What is the purpose of slope and aspect calculations?

Slope calculates the steepness, and aspect calculates the direction of the slope.

What are zonal statistics?

Summarizing raster values by zones defined by another dataset (e.g., catchments).

What is a global raster function?

An operation where the value of a pixel in the output raster depends on potentially all cells in the input raster.

Give an example of a global raster function.

Euclidean distance or least cost path analysis.

What is Euclidean distance?

The distance from a feature (point, line, or polygon) to all other cells in the raster.

What type of problems are raster techniques well suited for?

Overlay problems involving multiple criteria.

What is map overlay?

Combining raster inputs to derive a solution based on multiple criteria.

What is a hard threshold?

Treating each layer equally

What is weighted in map overlay?

Layers are weighted where some layers are more important than others.

What are examples of criteria in Wind Turbine example?

Wind speed, distance from road and land cover

What type of function is reclass?

local function

What were the findings from the study on global transition?

Land has been changing, typically from natural land or agriculture to urban over time

What was the main air pollution?

Acid rain

Is air pollution an example of map overlay?

Yes