Lesson 1.1 GIS Concepts, Data Types and Models

is a computer-based system used to collect, store, manage, analyze, and display geographic or spatial data.

Main functions of GIS

acquire geographic data

keep spatial data in databases

organize and update data

examine relationships and patterns

present information through maps, tables, and charts

GIS connects ___ with ___.

describes objects or phenomena based on their location on or near Earth's surface.

Describes where something is.

Describes what something is or what characteristics it has.

is data that contains information about the location, shape, and spatial relationships of geographic features.

Spatial data can be represented mainly using:

represents geographic features using points, lines, and polygons.

represents a feature with a specific location but no measurable area at the map scale.

Geometry: X, Y coordinates

represents a linear feature.

Geometry: A series of connected points/vertices

represents an area enclosed by lines.

Geometry: Closed series of connected vertices

represents geographic information as a grid of cells or pixels.

Each cell contains a value representing information about that location.

refers to the dimensions of each raster cell.

→ Higher spatial detail
→ More data

→ Lower spatial detail
→ Less data

Uses points, lines, polygons

Best for discrete features

Precise boundaries

Roads, parcels, buildings

Stores coordinates/vertices

Good for network analysis

Uses grid cells/pixels

Best for continuous phenomena

Cell-based boundaries

Elevation, temperature, imagery

Stores values in cells

Good for surface analysis

Represents separate, identifiable objects.

Usually represented well using vector data.

Represents phenomena that vary continuously across space.

Usually represented well using raster data.

contains descriptive information associated with geographic features.

names or descriptions

whole numbers

decimal numbers

dates and times

true/false

provides a method for identifying locations on Earth's surface.

Uses:
•Latitude
•Longitude

Usually measured in:
•Degrees
•Decimal degrees

Transforms Earth's curved surface onto a flat map using mathematical projection.

Coordinates are commonly expressed in:
•Meters
•Feet

is a mathematical method for representing the curved Earth on a flat surface.

Because Earth is curved, projecting it onto a flat map causes some form of

Common types of distortion:

a method for organizing and representing geographic information in a GIS.

Represents features as: Points → Lines → Polygons

Represents features as: Cells → Rows → Columns

Stores lines independently without explicitly storing their relationships.

Stores spatial relationships between features.

is organized into a matrixrid.

refers to the size of the smallest geographic area represented by a raster cell.

expresses the relationship between a distance on the map and the corresponding distance on the ground.

•Shows a smaller area
•More detail

•Shows a larger area
•Less detail

is information that describes a dataset.

GIS organizes geographic information into

Creates an area around a feature at a specified distance.

Cuts a dataset according to a boundary.

Combines multiple layers to analyze relationships.

Finds areas where features overlap.

Combines polygon features from multiple layers.

Selects features based on their location or spatial relationship.

GIS Workflow