Find nearest location coordinates in Land using python

Question

A geocode api returns no location information for coordinates in ocean/sea. For those records, I would like to find the nearest possible coordinates that has a valid location information (that is closest land coordinates) Below is the code for fetching location information by passing coordinates

import requests    
request_url = "https://api.mapbox.com/geocoding/v5/mapbox.places/{0}%2C{1}.json?access_token={2}&types=country&limit=1".format(lng,lat,key)
response = requests.get(request_url)
output = response.json()

I have no clue in finding the nearest location. I'm also new to Python

Sample output:

{'type': 'FeatureCollection',
 'query': [32.12, 54.21],
 'features': [{'id': 'country.10008046970720960',
   'type': 'Feature',
   'place_type': ['country'],
   'relevance': 1,
   'properties': {'short_code': 'ru', 'wikidata': 'Q159'},
   'text': 'Russia',
   'place_name': 'Russia',
   'bbox': [19.608673, 41.185353, 179.9, 81.961618],
   'center': [37.61667, 55.75],
   'geometry': {'type': 'Point', 'coordinates': [37.61667, 55.75]}}],
 'attribution': 'NOTICE: © 2020 Mapbox and its suppliers. All rights reserved. Use of this data is subject to the Mapbox Terms of Service (https://www.mapbox.com/about/maps/). This response and the information it contains may not be retained. POI(s) provided by Foursquare.'}

Output when the coordinates are ocean:

{'type': 'FeatureCollection',
 'query': [0, 0],
 'features': [],
 'attribution': 'NOTICE: © 2020 Mapbox and its suppliers. All rights reserved. Use of this data is subject to the Mapbox Terms of Service (https://www.mapbox.com/about/maps/). This response and the information it contains may not be retained. POI(s) provided by Foursquare.'}

Answer 1

Using Haversine Formula to find the nearest point (eg. city) based on latitude and longitude.

def dist_between_two_lat_lon(*args):
    from math import asin, cos, radians, sin, sqrt
    lat1, lat2, long1, long2 = map(radians, args)

    dist_lats = abs(lat2 - lat1) 
    dist_longs = abs(long2 - long1) 
    a = sin(dist_lats/2)**2 + cos(lat1) * cos(lat2) * sin(dist_longs/2)**2
    c = asin(sqrt(a)) * 2
    radius_earth = 6378 # the "Earth radius" R varies from 6356.752 km at the poles to 6378.137 km at the equator.
    return c * radius_earth

def find_closest_lat_lon(data, v):
    try:
        return min(data, key=lambda p: dist_between_two_lat_lon(v['lat'],p['lat'],v['lon'],p['lon']))
    except TypeError:
        print('Not a list or not a number.')
    
# city = {'lat_key': value, 'lon_key': value}  # type:dict()
new_york = {'lat': 40.712776, 'lon': -74.005974}
washington = {'lat': 47.751076,  'lon': -120.740135}
san_francisco = {'lat': 37.774929, 'lon': -122.419418}

city_list = [new_york, washington, san_francisco]

city_to_find = {'lat': 29.760427, 'lon': -95.369804}  # Houston
print(find_closest_lat_lon(city_list, city_to_find))

Which Yields:

{'lat': 47.751076, 'lon': -120.740135}  # Corresponds to Washington

Let's suppose you got four json answers from mapbox and you saved them in a list:

json_answers = list()  # = []

json_answers.append({'type': 'FeatureCollection', 
'query': [32.12, 54.21],
'features': [{'id': 'country.10008046970720960',
'type': 'Feature',
'place_type': ['country'],
'relevance': 1,
'properties': {'short_code': 'ru', 'wikidata': 'Q159'},
'text': 'Russia',
'place_name': 'Russia',
'bbox': [19.608673, 41.185353, 179.9, 81.961618],
'center': [37.61667, 55.75],
'geometry': {'type': 'Point', 'coordinates': [37.61667, 55.75]}}],
'attribution': 'NOTICE: ...'})

# I changed only the 'coordinates' value for this example
json_answers.append({'type': 'FeatureCollection', 
'query': [32.12, 54.21],
'features': [{'id': 'country.10008046970720960',
'type': 'Feature',
'place_type': ['country'],
'relevance': 1,
'properties': {'short_code': 'ru', 'wikidata': 'Q159'},
'text': 'Russia',
'place_name': 'Russia',
'bbox': [19.608673, 41.185353, 179.9, 81.961618],
'center': [37.61667, 55.75],
'geometry': {'type': 'Point', 'coordinates': [38.21667, 56.15]}}],
'attribution': 'NOTICE: ...'})

# I changed only the 'coordinates' value for this example
json_answers.append({'type': 'FeatureCollection', 
'query': [32.12, 54.21],
'features': [{'id': 'country.10008046970720960',
'type': 'Feature',
'place_type': ['country'],
'relevance': 1,
'properties': {'short_code': 'ru', 'wikidata': 'Q159'},
'text': 'Russia',
'place_name': 'Russia',
'bbox': [19.608673, 41.185353, 179.9, 81.961618],
'center': [37.61667, 55.75],
'geometry': {'type': 'Point', 'coordinates': [33.21667, 51.15]}}],
'attribution': 'NOTICE: ...'})

# The last answer is "null"
json_answers.append({'type': 'FeatureCollection',
'query': [0, 0],
'features': [],
'attribution': 'NOTICE: ...'})

coord_list = []
for answer in json_answers:
    if answer['features']:  # check if ['features'] is not empty
        # I'm not sure if it's [lat, lon] or [lon, lat] (you can verify it on mapbox)
        print(f"Coordinates in [lat, lon]: {answer['features'][0]['geometry']['coordinates']}")
        lat = answer['features'][0]['geometry']['coordinates'][0]
        lon = answer['features'][0]['geometry']['coordinates'][1]

        temp_dict = {'lat': lat, 'lon': lon}
        coord_list.append(temp_dict)

print(f"coord_list = {coord_list}")

point_to_find = {'lat': 37.41667, 'lon': 55.05}  # Houston
print(f"point_to_find = {point_to_find}")
print(f"find_closest_lat_lon = {find_closest_lat_lon(coord_list, point_to_find)}")

Which yields:

{'lat': 47.751076, 'lon': -120.740135}
Coordinates in [lat, lon]: [37.61667, 55.75]
Coordinates in [lat, lon]: [38.21667, 56.15]
Coordinates in [lat, lon]: [33.21667, 51.15]

coord_list = [{'lat': 37.61667, 'lon': 55.75}, {'lat': 38.21667, 'lon': 56.15}, {'lat': 33.21667, 'lon': 51.15}]

point_to_find = {'lat': 37.41667, 'lon': 55.05}

find_closest_lat_lon = {'lat': 38.21667, 'lon': 56.15}

Answer 2

Use reverse_geocode library in python to get nearest city with country.

Example:

import reverse_geocode

coordinates = (-37.81, 144.96), (31.76, 35.21)

reverse_geocode.search(coordinates)

Result:

[{'city': 'Melbourne', 'code': 'AU', 'country': 'Australia'}, {'city': 'Jerusalem', 'code': 'IL', 'country': 'Israel'}]