Introduction to Spatial Data Flashcards
Describe the two spatial data models used to represent real-world features and phenomena, and use ArcGIS Pro to explore vector and raster data
What are continuous features?
Represent real-world phenomena that do not have well-defined boundaries (elevation, temperature, rainfall)
What are discrete features?
Represent real-world features that have well-defined boundaries (rivers, buildings, trees)
How do you differentiate between continuous and discrete?
If you need to average something, then it’s continuous.
Vector Geometry
What is a point?
Represents discrete objects
x, y coordinate or vertex
Vector Geometry
What is a line?
Represents discrete objects
two or more connected x, y coordinate locations or vertices
Vector Geometry
What is a polygon?
Represents discrete objects
three or more connected x, y coordinate locations or vertices, forming a closed loop
Describe vector attributes
Information is stored in an attribute table. Each row, or record, represents one feature while each column, or field, represents an attribute. They can be user defined or automatically generated.
Describe the raster data model.
- Represents the surface of the earth as a grid of equally sized cells
- All images are raster, but not all rasters are images
- May contain several pieces of info called bands (which represent data captured at a certain wavelength)
- Multiband rasters contain two or more bands of info from different sensors
Describe raster attributes.
They’re stored in cells. They’re usually created automatically by the sensors. In multiband, each cell will contain attributes from each band. Value or attribute for each cell is determined by the average - smaller cells cover smaller area and will have greater detail. The size of each cell is the raster resolution.
What are the 6 raster data types?
Continuous, discrete, imagery, scanned maps, videos, mosaics.
What is a continuous raster data type?
Any continuous data such as rainfall (think averaging)
What is a discrete raster data type?
Anything with a defined boundary such as soil types.
What is an imagery raster data type?
They’re produced using a camera or other sensor. They’re considered continuous.
What is a scanned map raster data type?
They’re static raster images of an original map. They look like they have vector features, but they’re just depicted. Scanned maps will still use a grid system.
What is a video raster data type?
They can also be stored in a GIS. They are sequences of raster images.
