Coordinate Reference Systems

Working with Geospatial Data in Python

Joris Van den Bossche

Open source software developer and teacher, GeoPandas maintainer

Coordinate Reference System (CRS)

Location of the Eiffel Tower:

POINT (2.2945 48.8584)

→ The Coordinate Reference System (CRS) relates the coordinates to a specific location on earth.

Degrees of latitude and longitude.

E.g. 48°51′N, 2°17′E

Used in GPS, web mapping applications...

Attention!
in Python we use (lon, lat) and not (lat, long)

(x, y) coordinates are usually in meters or feet

Albers Equal Area projection

Mercator projection

Projected size vs actual size (Mercator projection)

proj4 string

Example: +proj=longlat +datum=WGS84 +no_defs

Dict representation:

{'proj': 'longlat', 'datum': 'WGS84', 'no_defs': True}

EPSG code

Example:

EPSG:4326 = WGS84 geographic CRS (longitude, latitude)

The .crs attribute of a GeoDataFrame/GeoSeries:

import geopandas
gdf = geopandas.read_file("countries.shp")
print(gdf.crs)

{'init': 'epsg:4326'}

Working with Geospatial Data in Python