L03 Demo: Spatial Data Models

MODE: VECTOR — Contour Lines

Vector vs Raster Explorer

Same terrain, two fundamentally different data models

View Mode

Low

High

0m200m400m600m780m

Raster Opacity

0%80%100%

Data Comparison

Area:4 km x 4 km

Raster grid:500 x 500 cells

Raster resolution:8 m per cell

Raster values:250,000 elevation values

Vector contours:—

Contour interval:50 m

Click any contour line to see its geometry type, coordinate count, and elevation.

Feature Info (click a contour)

Geometry type:—

Vertex count:—

Elevation:—

Position (km):—

Case Study: This 4 km x 4 km section of Banks Peninsula terrain is shown as vector contour lines (every 50 m) and as a raster DEM grid (250,000 cells at 8 m resolution). The same real-world elevation is captured in fundamentally different ways.

Guided Questions

Toggle between Vector and Raster DEM views. Which representation makes it easier to identify a specific elevation (e.g., the 200 m contour)? Which better shows the continuous terrain surface?

The DEM has 8 m resolution (250,000 cells). The contour lines have far fewer vertices. What information is lost between contour lines that the raster preserves? What does the vector preserve that the raster does not?

Click a contour line and note the vertex count. Each vertex stores an [x, y] coordinate pair. How does the data storage per elevation value compare between the vector model (vertices along lines) and the raster model (one value per cell)?

If you needed to calculate the slope gradient at every point across this area, which data model would you use — vector contours or the raster DEM? Why?