Vector vs raster data models in GIS

GIS stores geography in two main ways: vector (points, lines, polygons) and raster (grids of cells). Cadastral and revenue work is mostly vector; elevation, satellite images, and continuous surfaces are often raster. Knowing the difference helps you choose tools (e.g. parcel checker vs image overlay).

1. Vector data model

• Built from vertices and paths — points, polylines, polygons.
• Best for discrete features with clear boundaries: survey numbers, roads, buildings, village limits.
• Attributes (owner, survey number, area) attach cleanly to each feature.
• Editing individual parcels and topology (shared boundaries) is natural.
• Typical files: Shapefile, GeoJSON, GPKG (vector layers).

2. Raster data model

• Built as a grid of cells (pixels), each cell holding one value.
• Best for continuous phenomena: elevation, rainfall, land-cover classification, scanned maps.
• Aerial / satellite imagery is raster by nature.
• Neighbourhood analysis (cost path, density, edge effects) is often easier on grids.
• Resolution (cell size) controls both detail and file size.

3. Side-by-side comparison

Topic	Vector	Raster
Structure	Vertices + paths (simpler feature model)	Regular grid (structure simple; large arrays can be heavy)
Best for	Parcels, lines, points with IDs	Surfaces, imagery, continuous fields
Attributes	Rich tables per feature	Usually one value per cell (multi-band for images)
Editing features	Move vertices, split polygons	Cell-by-cell or reclassify; not parcel-friendly
Overlay	Efficient geometric overlay if topology is clean	Map algebra (add/multiply grids) is straightforward
AP survey day-to-day	FMB digitalisation, resurvey parcels, adangal joins	Orthophoto background, DEM, scanned village maps

4. What to use in the field toolkit

• Vector: Online GIS viewer, parcel boundary checker, coordinate area tools.
• Raster: load imagery under vectors for ground-truthing context; do not treat a fuzzy image boundary as a legal cadastral limit.

5. One-line rule

Boundaries and ownership → vector. Continuous surface or photo → raster. Many projects use both: parcels (vector) drawn on orthophoto (raster).