Vector vs. Raster: How Digital Maps Store the World

Zoom into a road on Google Maps and the street lines stay razor-sharp no matter how close you get. Zoom into the satellite photo view of the same spot, and eventually you see blurry squares of color. That difference isn't an accident — it's two completely different ways of storing map data: vector and raster.

- The difference between vector data (points, lines, polygons) and raster data (pixel grids) - Why vector lines never get blurry when you zoom in, but raster images do - Real file formats cartographers use for each type (.shp vs .tif) - How to decide which data type fits a mapping job

Raster data stores a map as a grid of colored squares called pixels, the same way a digital photo works. A satellite image of Los Angeles might be a grid 10,000 pixels wide by 10,000 pixels tall, with each pixel holding a color value captured by a sensor orbiting 700 kilometers overhead. Because every square inch of ground gets its own pixel, raster files can get huge — a single high-resolution satellite scene can run past 500 megabytes. Raster is the right tool whenever the map data is continuous, like elevation, temperature, or a photograph of the Earth's surface. The common file format cartographers use is GeoTIFF (.tif), a TIFF image with map coordinates baked into the file.

Vector data skips pixels entirely and stores shapes as mathematical coordinates. A road becomes a list of latitude/longitude points connected by a line; a country border becomes a polygon defined by hundreds of connected points; a city becomes a single point with a label. Because a line is just math (start point, end point, and the path between), you can zoom in infinitely and the edges stay perfectly crisp — there's no pixel grid to run out of. Vector data is also compact: the entire road network of a mid-sized city might fit in a few megabytes, versus hundreds of megabytes for a raster image covering the same area. The standard vector file format is the shapefile (.shp), created by Esri in 1998 and still the most common format cartographers trade files in today.

Open any modern digital map, like Google Maps or Apple Maps, and you're usually looking at vector and raster layered together. The roads, labels, building outlines, and borders are vector — that's why they stay sharp and re-draw instantly when you rotate the map. Switch to satellite view and you're now looking at raster imagery stitched together from airplanes and satellites like Landsat 9, which photographs the entire planet every 16 days. Cartographers building hiking apps often combine both: a raster hillshade layer showing terrain texture, with vector trail lines drawn crisply on top.

Professional cartographers pick data types based on what they're mapping, not personal preference. Discrete features with clear edges — roads, buildings, political borders, property lines — belong in vector format because they need to stay crisp and take up little storage space. Continuous surfaces that change gradually — elevation, rainfall, satellite photography, temperature maps — belong in raster format because every location needs its own measured value. Many professional GIS tools, like the free and open-source QGIS, let mapmakers layer both types in a single project, which is exactly what you see in weather apps that overlay vector city labels on top of a raster radar image.