Dealing with projections

One of the challenges of working with geospatial data is that geodetic locations (points on the Earth's surface) are often mapped onto a two-dimensional Cartesian plane using a cartographic projection. We looked at projections in the previous chapter: whenever you have some geospatial data, you need to know which projection that data uses. You also need to know the datum (model of the Earth's shape) assumed by the data.

A common challenge when dealing with geospatial data is that you have to convert data from one projection or datum to another. Fortunately, there is a Python library that makes this task easy: pyproj.

pyproj

pyproj is a Python "wrapper" around another library called PROJ.4. PROJ.4 is an abbreviation for version 4 of the PROJ library. PROJ was originally written by the US Geological Survey for dealing with map projections and has been widely used in geospatial software for many years. The pyproj library makes it possible to access...