Check your understanding
Before diving into this week’s Python lesson, you should already be familiar with some basic spatial data file formats and projection definitions, such as these:
Shapefile: a vector data format for storing location information and related attributes.
A shapefile consist of several files with a common prefix that need to be stored in the same directory.
.dbf are required file extensions in a shapefile. Other file extensions are not required,
but for example the file extension
.prj is often essential. More information about Shapefile file extensions
The shapefile format is developed by ESRI.
GeoPackage: an open source format for storing and transferring geospatial information.
GeoPackages are able to store both vector data and raster data. In more detail, GeoPackage is a container for
an SQLite database with a
.gpkg extension (all in one file!). The GeoPackage format is governed by the Open GeoSpatial Consortium.
More information at: https://www.geopackage.org/
CRS: Coordinate reference systems define how coordinates relate to real locations on the Earth. Geographic coordinate reference systems commonly use latitude and longitude degrees. Projected coordinate reference systems use x and y coordinates to represent locations on a flat surface. You will learn more about coordinate reference systems during this lesson!
Datum: defines the center point, orientation, and scale of the reference surface related to a coordinate reference system. Same coordinates can relate to different locations depending on the Datum! For example, WGS84 is a widely used global datum. ETRS89 is a datum used in Europe. Coordinate reference systems are often named based on the datum used.
EPSG: EPSG codes refer to specific reference systems. EPSG stands for “European Petroleum Survey Group” that originally published a database for spatial reference systems. For example, EPSG:3067 refers to coordinate reference system ETRS-TM35FIN which is commonly used in Finland. EPSG:4326 refers to WGS84. You can search for EPSG codes at: https://spatialreference.org/