GIS and Geospatial Data Basics

What is GIS?¶

A geographic information system (GIS) captures, manages, analyzes, and presents spatial data. Common applications include logistics, urban planning, resource management, and telecommunications.

Geospatial data¶

Geospatial data combines attributes with a location or shape.

Vector data¶

Point: location
LineString: road or route
Polygon: area or boundary
Multi-geometries and GeometryCollection: groups of geometries

Raster data¶

A raster is a grid of cells, used for imagery, elevation, and other continuous data.

Coordinate reference systems¶

A coordinate reference system (CRS) relates coordinates to places on Earth.

EPSG:4326: longitude and latitude
Projected CRS: useful for measuring distance and area
set_crs(): assigns a CRS; to_crs(): transforms coordinates

OpenStreetMap¶

Node: a point
Way: an ordered list of nodes
Relation: a group of nodes, ways, or relations

Software¶

Desktop: QGIS, ArcGIS Pro
Python: GeoPandas, Shapely, Rasterio
Conversion and processing: GDAL
Databases: PostGIS, Oracle Spatial, ArcGIS enterprise geodatabase

Storage formats¶

Format	Data	Typical use
GeoPackage (`.gpkg`)	Vector, tiled raster	Portable general-purpose storage
GeoJSON (`.geojson`)	Vector	Web and data exchange
GeoParquet (`.parquet`)	Vector	Columnar analytics
Shapefile (`.shp` and companion files)	Vector	Legacy interoperability
GeoTIFF / COG (`.tif`)	Raster	Imagery and elevation
PostGIS	Vector, raster	Large or shared datasets

CSV files may store geometries as WKT, but usually lack standardized spatial metadata.

Minimal GeoPandas example¶

import geopandas as gpd

gdf = gpd.read_file("data.gpkg")
print(gdf.crs)
print(gdf.geometry.geom_type.value_counts())