Buffering one side of line using GeoPandas

Question

I have these transects I've buffered as training data, but now we had "edges" defined where we need a simple buffer on ONE side of the line. I run my scripts within Jupyter Notebooks, so it needs to work standalone. Right now my buffer code looks like this:

lines['geometry'] = lines.buffer(1, cap_style=3)

lines.to_file(linesBufferFolder + "\\Lines_Buffer")

This creates a 1m buffer on both sides with end caps. Like this:

I essentially need to bisect that polygon, and only keep the "left" side based on the order which the points go. My initial thought was to use a one sided buffer, but I can't find any documentation for that in GeoPandas Geometric Manipulation documentations.

My other idea was to simply erase half of the polygon I currently have, but again, to get that overlay I would think I would need to buffer the other side, bringing me back to my original issue. I know how to manually do one side buffers, but finding a Python library that uses it other than ArcPy is stumping me.

Answer 1

You can do single side buffer using Geopandas but you need shapely version 1.7 or upper version (due to https://github.com/Toblerity/Shapely/issues/727#issuecomment-499900749) I do reprojection to a meters based projection in my sample as buffer unit is the projection unit and using degrees is not recommended.

import geopandas

lines = geopandas.read_file('https://d2ad6b4ur7yvpq.cloudfront.net/naturalearth-3.3.0/ne_50m_rivers_lake_centerlines.geojson')

# Buffer negative or positive depending if left or right buffer compared to line orientation
buffered_lines_positive = lines.to_crs('EPSG:3857').buffer(20000, single_sided=True)
buffered_lines_negative = lines.to_crs('EPSG:3857').buffer(-20000, single_sided=True)