Work in meters

Most files arrive in WGS 84 (degrees), but field work happens in meters. shapelib gives you three levels of convenience.

Let the methods handle it

Measurements are geodesic and meter-based methods reproject internally — calculate_length, calculate_area, buffer_m need nothing from you:

lines = read_file("lines.shp")   # WGS 84
lines.calculate_length()         # accurate, no reprojection needed

Reproject temporarily — temp_crs

For a metric operation in the middle of a workflow, the temp_crs context manager switches the CRS and guarantees it switches back:

with lines.temp_crs(lines.estimate_utm_crs() or "EPSG:31982"):
    # coordinates are in meters inside this block
    ...

Reproject explicitly

When a whole pipeline works in meters (like the line tools, whose thresholds are in CRS units), convert once and convert back at the end:

lines.to_utm()           # project to the detected UTM zone

# ... metric work here ...

lines.to_original_crs()  # back to the CRS the file was read with

to_wgs84() is also available as a shortcut to EPSG:4326.

Note

to_utm() picks the UTM zone from the data. For data spanning multiple UTM zones, choose the CRS yourself with geopandas’ to_crs.