Obtain Coordinates Of A Polygon / Multi-polygon Around A Point In Python

I am using plotlys scattermapbox to draw a polygon around a point object. I'd like to draw a polygon that covers 'x' mile radius from a POI. I found this that is helpful: https://p

Solution 1:

• using this helper https://github.com/Turbo87/utm to transform between GPS (WSG84 / EPSG:4326) and UTM
• you expressed that POI circle/polygon radius as a distance x miles hence need to work with UTM projections to express radius as a distances
• have used UK hospitals as sample POI data. Without significant zoom levels circles will not display as they are only 1 mile radius. It will be simple to plug in any other dataframe with latitude and longitude columns
• used a scatter mapbox as sample plot, then added layer that are POI circles/polygons

import shapely.geometry
import utm
import pandas as pd
import geopandas as gpd
import requests, io, json
import plotly.express as px

# need to use UTM to express radius as a distance. UTM is zoned, so if GPS coords are very widely distributed
# distance will be incorrect.  zone is estimated from first GPS coordinate
# returns geopandas dataframe re-projected to GPS co-ordinates
# radius is expressed in metres
def circles(lonlat, radius=10 ** 4):
    
    utm_coords = utm.from_latlon(lonlat[:, 1], lonlat[:, 0])
    utmcrs = gpd.GeoDataFrame(
        geometry=[shapely.geometry.Point(lonlat[0, 0], lonlat[0, 1])], crs="EPSG:4326"
    ).estimate_utm_crs()

    return gpd.GeoDataFrame(
        geometry=[
            shapely.geometry.Point(easting, northing).buffer(radius)
            for easting, northing in zip(utm_coords[0], utm_coords[1])
        ],
        crs=utmcrs,
    ).to_crs("EPSG:4326")


# get some public addressess - hospitals.  data that can be scattered
dfhos = pd.read_csv(io.StringIO(requests.get("http://media.nhschoices.nhs.uk/data/foi/Hospital.csv").text),
    sep="¬",engine="python",)


# generate circles of diameter 1 mile, which is 1609.34 metres
gdf = circles(dfhos.head(20).loc[:, ["Longitude", "Latitude"]].values, radius=1609.34)

fig = (
    px.scatter_mapbox(
        dfhos.head(20),
        lat="Latitude",
        lon="Longitude",
        color="Sector",
        hover_data=["OrganisationName", "Postcode"],
    )
    .update_traces(marker={"size": 10})
    .update_layout(
        mapbox={
            "style": "open-street-map",
            "zoom": 9,
            "center":{"lat":gdf.loc[0,"geometry"].centroid.y, "lon":gdf.loc[0,"geometry"].centroid.x},
            "layers": [
                {
                    "source": json.loads(gdf.geometry.to_json()),
                    "below": "traces",
                    "type": "line",
                    "color": "purple",
                    "line": {"width": 1.5},
                }
            ],
        },
        margin={"l": 0, "r": 0, "t": 0, "b": 0},
    )
)
fig.show()