Module 1 -- Intro to Data Types

Spatial Data

Data that represents the location and characteristics of features on Earth using geographic coordinates

Spatial Data Model

A method used in GIS to digitally represent real-world geographic features

Vector Data

A spatial data model that represents geographic features using coordinates to define points, lines, and polygons

Point

A zero-dimensional vector feature defined by a single (x, y) coordinate representing a specific location

Line (Polyline)

A one-dimensional vector feature formed by connecting multiple vertices to represent linear features

Polygon

A two-dimensional vector feature formed by closed lines where the first and last coordinates are the same, representing areas

Vertex

A bend or turning point along a line or polygon that does not imply connectivity

Node

A point where two or more lines or polygons intersect, implying connectivity

Attribute Data

Non-spatial information stored in a database and linked to vector features through a unique identifier

Vector Layer

A collection of vector features of the same geometry type (points, lines, or polygons)

Spaghetti Data Model

A vector data structure where features are stored as independent coordinate strings with no topology or explicit spatial relationships

Topological Data Model

A vector data structure that explicitly stores spatial relationships such as connectivity, adjacency, and shared boundaries

Topology

The set of rules defining spatial relationships between vector features, including connectivity, area definition, and contiguity

Connectivity (Arc–Node Topology)

A topological rule describing how lines connect at nodes, enabling movement and network analysis

Arc

A line segment with a defined from-node and to-node used in topological vector models

From-Node

The starting node of an arc in a vector network

To-Node

The ending node of an arc in a vector network

Area Definition (Polygon–Arc Topology)

A topological rule where polygons are defined by a series of connected arcs stored once and shared between adjacent polygons

Contiguity (Adjacency)

A topological relationship where polygons sharing a boundary are considered adjacent

Universe Polygon

A polygon representing the area outside the study region in a topological dataset

Open Polygon

A polygon that does not fully close, violating topology rules

Unlabeled Polygon

A polygon that lacks associated attribute data

Sliver

A small unintended polygon created by misaligned shared boundaries

Overshoot

A line that extends beyond the node it should connect to

Undershoot

A line that does not extend far enough to reach the intended node

Dangling Node

A node connected to only one line; may be an error or a valid dead-end

Raster Data

A spatial data model that represents geographic information as a grid of cells, each containing a value

Cell (Pixel)

The smallest unit of a raster dataset that stores a single value

Discrete Raster

A raster dataset where each cell represents a distinct category or class

Continuous Raster

A raster dataset representing smoothly varying phenomena with gradual value changes across space

Raster Band

A single layer of values within a raster dataset, often representing a specific wavelength or attribute

Spatial Resolution

The size of raster cells; smaller cells indicate higher spatial resolution

Data Volume

The amount of data required to store a raster dataset, which increases with higher spatial resolution

Interpolation

A method used to estimate values for locations where raster data is missing

Spatial Referencing

The process of assigning geographic coordinates to raster cells so they align correctly in GIS

Resolution vs Accuracy

The concept that higher spatial resolution does not necessarily mean higher data accuracy

Shapefile

A common vector data format used to store geometry and attributes

GeoJSON

A vector data format based on JSON used for web mapping and data exchange

KML

A vector file format commonly used for displaying geographic data in Google Earth

GeoTIFF

A raster file format that includes geographic metadata within the image file

Metadata

Documentation that describes spatial data, including source, resolution, projection, and date of acquisition