Using Raster Data Flashcards
What are rasters?
Are a way of viewing and analysing continuous data.
What is continuous data?
Continuous data is a single variable or piece of information that is defined at every location.
What is the difference between Raster, Grid and a surface?
A Raster, Grid and a Surface are data structures and the same thing. They are all a set of cells arranged in rows and columns and each of the cells has a value.
Ordinance survey MasterMap data is what kind of data?
It is vector data made up of polygons.
Give a difference between Raster data and Vector data.
Raster data can have only one attribute and vector data can have any number
How can we create Raster data?
It is through sampling taking measurements of soil moisture for example and record the location of those measurements also through surveying collecting individual points using GPS.
What give us a measure of how spatially clustered points are?
Moran’s Index gives us a measure of how spatially clustered points are.
Define interpolation.
A process used to estimate an intermediate value of one (dependent) variable which is a function of a second (independent) variable when values of the dependent variable corresponding to several discrete values of the independent variable are known.
How does ArcGIS use interpolation?
interpolation by, for every Raster location for every cell in your raster It will look at the sample location around that pixel location calculate what t those values of are and then use a function to calculate the value of the pixel.
How can you analyse height data?
1) Visualisation
2) Viewshed
3) Line of Sight
4) Volumes Hydrological Analysis
What is a DEM?
DEM (Digital Elevation Model): Set of regularly or irregularly spaced height values.
What is a DTM?
DTM (Digital Terrain Model): can contain information about terrain surface- ridge lines, spot heights, troughs, coast/shorelines, drainage lines, faults, peaks, pits, passes, etc.
What is a DSM?
DSM (Digital Surface Model): Set of regularly or irregularly spaced height values. But can include features that extrude above the base topography.
What is visualisation?
Visualisation is the process of looking at out data in 3D rather than 2D. For example using heights to move the data on the Z scale
How can contour be created?
Through a DEM.
