Iterate over geopandas dataframe returning nearest point on each LineString

Question

I'd like to iterate through a GeoDataFrame that contains a column of LineStrings and return a list of points; one from each LineString that is closest to a reference point.

#### .  Import data from Overpass API

import overpy

api = overpy.Overpass()

pHigh = api.query("""
(
node[highway=primary](34.978011,-116.697296, 36.747345, -113.976445);
way[highway=primary](34.978011,-116.697296, 36.747345, -113.976445);
rel[highway=primary](34.978011,-116.697296, 36.747345, -113.976445);
);
(._;>;);
out center;
""")

##### . Make a shapefile

import fiona 
from fiona.crs import from_epsg
schema = {'geometry': 'LineString', 'properties': {'Name':'str:80'}}
shapeout = "test.shp"
with fiona.open(shapeout, 'w',crs=from_epsg(4326),driver='ESRI 
Shapefile', schema=schema) as output:
    for way in pHigh.ways:
        # the shapefile geometry use (lon,lat) 
         line = {'type': 'LineString', 'coordinates':[(node.lon, 
        node.lat) for node in way.nodes]}
        prop = {'Name': way.tags.get("name", "n/a")}
        output.write({'geometry': line, 'properties':prop})  


##### .  Make a geopandas dataframe

import geopandas as gpd

gpanda = gpd.read_file("test.shp")  


##### . Point to measure distance from 

from shapely.geometry import LineString, Point

lat=36.069173
long= -115.013759

point=Point(lat,long)


##### .  return the coordinates for the nearest point on the linestring 
#####    relative to the reference point ('point').  Doesn't Work!

result=[]
for index, row in gpanda.iterrows():
    result += row.geometry.interpolate(row.geometry.project(point))

##### . Seems to work for individual rows...

gpanda.geometry[1:2].interpolate(gpanda.geometry[1:2].project(point))

This may be the wrong approach, I really just want an accurate measure of the nearest highway to many points. This way I would have the nearest point from each highway, which I could use to calculate the great circle distance from the reference point and find the minimum.

Answer 1

You might want to try rtree. It is the fastest way to retrieve nearest geometries especially when you have a large number of geometries involved. An example of geopandas itself implementing r-tree method is provided by the excellent Geoff Beoing