Introduction to Spatial Data Flashcards
Known as geographic information or geographic data, can be a representation on a map of real-world features and phenomena; however, it can also be any information with a location attached to it, whether on a map or not
Spatial Data
What has location and attribute information, storing information about where something is with information about something is?
GIS
Most basic way to categorize GIS data into two categories
Discrete or Continuous
What represents real-world features that have well-defined boundaries. A _________ feature is distinct from the other features around it. For example, a river is a _________ feature: You can be in the river, out of the river, or half-in and half-out of the river, but there is a distinct place where you stop being dry and begin getting wet.
Discrete - discrete data
What represents real-world phenomena that do not have well-defined boundaries. Examples of _________ phenomena include elevation, temperature, or rainfall. In each of these examples, there are no distinct places where the phenomena simply stop; values may change abruptly, but the phenomena continue to be measured. Hint: It makes sense to take the average of values.
Continuous data
Data model represents discrete objects on the surface of the earth, such as streetlights, roads, and buildings, as point, line, and polygon (area) features, respectively.
Vector geometry
A single x,y coordinate location, or vertex
Point
Made of two or more connected x,y coordinate locations, or vertices.
Line
Made of three or more connected x,y coordinate locations, or vertices, forming a closed loop.
Polygon
Map of downtown San Diego, California, shows the buildings, water, and land features as polygon features; roads and public transportation routes are shown as lines.
Vector Map
Points, lines, and polygons are comprised of both geometry and attributes, which provide additional information about the feature.
Vector attributes
Map Scale: more zoomed out, less details. City represented by point
Small Scale
A way to remember the difference is that a building feature on a large-scale map will appear large and detailed, while the same building on a small-scale map will appear small (or disappear altogether).
Map Scale: More zoomed in, more details. City represented by polygon
Large Scale
A way to remember the difference is that a building feature on a large-scale map will appear large and detailed, while the same building on a small-scale map will appear small (or disappear altogether).
What represents the surface of the earth as a grid of equally sized cells. An individual cell represents a portion of the earth, such as a square meter or a square mile. Each cell contains the information for that part of the earth.
Raster Data Model
Raster vs. Image
The terms “raster” and “image” are often used interchangeably, but they should not be. An image is a 2D pictorial representation, while a raster is the data model used to store information in rows and columns of cells. All images are rasters, but not all rasters are images. For example, a dataset that shows rainfall levels is considered a raster but is not an image.
