Skip to content

Vector Data

Goal: Understand vector data — what it is, the three geometry types, common file formats, and when to use it.

What you'll learn

  • The three vector geometry types
  • Common formats: shapefile, GeoPackage, GeoJSON, file geodatabase
  • When to use vector vs raster

What is vector data?

Vector data represents the world as discrete shapes with exact coordinates.

flowchart LR
    V[Vector Data] --> P[Points]
    V --> L[Lines]
    V --> Pg[Polygons]

    P --> Px[Trees, ATMs, accidents,<br/>cities at small scale]
    L --> Lx[Roads, rivers, pipelines,<br/>flight paths]
    Pg --> Pgx[States, parcels, lakes,<br/>buildings]

    classDef root fill:#4338ca,stroke:#312e81,color:#fff
    class V root
    classDef type fill:#eef2ff,stroke:#4338ca,color:#312e81
    class P,L,Pg type

Points

A single location: (x, y) or (lat, long).

Use cases
ATMs, fire hydrants, GPS pings, accident locations, store locations, sample sites

Lines (Polylines)

A sequence of connected points.

Use cases
Roads, rivers, pipelines, power lines, flight paths, transit routes

Polygons

A closed shape with an inside and outside.

Use cases
Countries, states, parcels, buildings, lakes, census tracts, zoning

Multi-geometries

A single feature can have multiple parts:

  • Multipoint — a feature is multiple points (e.g., a school district's bus stops)
  • Multilinestring — a river system with branches
  • Multipolygon — a country with islands (Hawaii is one feature with 8 polygons)

Common vector formats

Format Extension Notes
Shapefile .shp + 3–7 sidecar files Old (1990s) but still everywhere. 2 GB limit, 10-char field names.
GeoPackage .gpkg Modern open standard. Single file, multiple layers, no size limit.
GeoJSON .geojson / .json Web-friendly text format. Great for sharing and APIs.
File Geodatabase .gdb (folder) Esri's native format. Used heavily in ArcGIS Pro.
KML/KMZ .kml / .kmz Google Earth format.

Modern recommendation

Use GeoPackage or File Geodatabase for production work. Use GeoJSON for web sharing. Avoid shapefiles for new projects.

Anatomy of a feature

Every vector feature has:

  1. Geometry — the shape (point/line/polygon coordinates)
  2. Attributes — a row in the attribute table
  3. Spatial reference — its CRS

You can think of a vector layer as a spreadsheet where one column is geometry. → See Attribute Tables.

Vector vs raster — when to use vector

✅ Use vector when:

  • Features have clear boundaries (a building, a parcel, a river)
  • You need to attach attributes to features
  • Output will be printed at varying scales (vectors stay sharp)

❌ Don't use vector for:

  • Continuous phenomena (elevation, temperature, satellite imagery)
  • Pixel-based analysis

→ Full comparison: Vector vs Raster tutorial

Topology

Topology is the spatial relationship between features:

  • Adjacency (which polygons share an edge?)
  • Connectivity (are these roads connected?)
  • Containment (is this point inside that polygon?)

ArcGIS Pro has dedicated topology tools to enforce rules like "polygons must not overlap" or "lines must be connected at endpoints."

Practice

Try this in ArcGIS Pro

  1. Create a new project.
  2. Download US states (TIGER/Line) — that's a polygon layer.
  3. Download US interstates — that's a line layer.
  4. Download US airports — that's a point layer.
  5. Open each layer's attribute table. Notice the rows = features.
  6. Right-click a layer → Properties → Source to see its CRS and format.

Next up

→ Raster Data — the pixel side of GIS.