[PYTHON] Batch convert LineString coordinate strings with Shapely + Pyproj

A memorandum regarding the implementation of the coordinate conversion process (WGS84-> UTM) of WKT format LineString in Python.

Execution environment

Python: v3.8.5 Library used: Shapely = 1.7.0, Pyproj = 3.0.0.post1

Processing content / implementation code

For the coordinate string of LineString read by Shapely, batch coordinate transformation with Transformer.itransformer of Pyproj with the specified EPSG code

transform_linestr.py

from pyproj import Transformer
from shapely import wkt
from shapely.geometry import LineString

WGS84_EPSG = 4326
UTM_EPSG = 6691


def main():
    #WKT format LineString load
    linestr_wkt = "LINESTRING (138.385554841666 34.9748902437125, 138.385886903329 34.9752925491883, 138.38621257919 34.9757140120678, 138.386397767425 34.97612270334488)"
    linestr = wkt.loads(linestr_wkt)

    #Coordinate conversion from WGS84 to UTM
    trans_linestr = transform_linestr(linestr, WGS84_EPSG, UTM_EPSG)

    #Coordinate reconversion from UTM to WGS84(The value may change slightly when the accuracy of the original coordinates is high.)
    re_trans_linestr = transform_linestr(trans_linestr, UTM_EPSG, WGS84_EPSG)

    print("Load WKT:  ", linestr)
    print("WGS84->UTM:", trans_linestr)
    print("UTM->WGS84:", re_trans_linestr)


def transform_linestr(linestr: LineString, from_epsg: int, to_epsg: int) -> LineString:
    """LineString coordinate conversion process in the specified EPSG code

    Args:
        linestr (LineString):Coordinate conversion source LineString
        from_epsg (int):Conversion source EPSG code
        to_epsg (int):Conversion destination EPSG code

    Returns:
        LineString:LineString after coordinate conversion
    """
    transformer = Transformer.from_crs(from_epsg, to_epsg)
    trans_coords = transformer.itransform(linestr.coords, switch=True)
    return LineString(trans_coords)


if __name__ == "__main__":
    main()

Execution output result

Load WKT:   LINESTRING (138.385554841666 34.9748902437125, 138.385886903329 34.9752925491883, 138.38621257919 34.9757140120678, 138.386397767425 34.97612270334488)
WGS84->UTM: LINESTRING (3873381.187880124 261326.0666616608, 3873425.024292707 261357.5560269007, 3873471.001297946 261388.5176213919, 3873515.897231507 261406.6137873351)
UTM->WGS84: LINESTRING (138.385554841666 34.9748902437125, 138.385886903329 34.9752925491883, 138.38621257919 34.9757140120678, 138.386397767425 34.97612270334487)

Shapely + Pyproj made it very easy to implement the coordinate sequence conversion process. Pyproj convenient.

reference

• Pyproj API Documentation Transformer -High-speed geodetic conversion with Pyproj