Where Am I? Finding coordinates with the Google Maps Geocoding API
Where Am I?
Finding coordinates with the Google Maps Geocoding API
In this blog post, you will learn how to find the latitude and longitude of an address and understand each step of the process.
What is the Google Maps Geocoding API?
Geocoding is a process that finds the GPS coordinates of a street address. The Google Maps Geocoding API provides an easy way to access this information using an HTTP Request.
Getting Started
Before you start using the Geocoding API, you must get an API key. The API key is added to your a app or website and tracks the API requests linked to your project for billing purposes. Don’t worry, it takes a very large number of hits for Google to start charging you.
Once you get your API key, you can begin formatting your Geocoding API request. The Geocoding API request is formatted like this:
https://maps.googleapis.com/maps/api/geocode/OUTPUT_FORMAT?PARAMETERS
OUTPUT_FORMAT must be replaced with either json or xml. json indicates that the output will be in JavaScript Object Notation (JSON), and xml indicates that the output will be in XML. This tutorial will focus on JSON outputs.
PARAMETERS must include an address and your API key. For the address 180 Main Street, Andover, MA 01810, the request would be:
https://maps.googleapis.com/maps/api/geocode/json?address=180+Main+Street,+Andover,+MA+01810&key=YOUR_API_KEY
This request gives you the output:
{
"results" : [
{
"address_components" : [...],
"formatted_address" : "Holmes Library, 180 Main St, Andover, MA 01810, USA",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 42.6473773,
"lng" : -71.1319472
},
"southwest" : {
"lat" : 42.6469545,
"lng" : -71.1326112
}
},
"location" : {
"lat" : 42.6471421,
"lng" : -71.13231859999999
},
"location_type" : "ROOFTOP",
"viewport" : {
"northeast" : {
"lat" : 42.6485148802915,
"lng" : -71.1309302197085
},
"southwest" : {
"lat" : 42.6458169197085,
"lng" : -71.13362818029151
}
}
},
"place_id" : "ChIJjQTtee0I44kRsa28CJ8UMW0",
"types" : [ "premise" ]
}
],
"status" : "OK"
}
Please note that "address components" within "results" has been redacted.
Our JSON response has two root elements: "results" and "status". "results" contains the geocoded data about our address, and "status" contains metadata about our request that is helpful for debugging.
We can also see that the latitude and longitude of our address are located under "results" → "geometry" → "location" as "lat" and "lng".
Once we get the data, we can parse the JSON to extract the latitude and longitude with a simple python method:
def geocode(address):
address = urllib.parse.quote_plus(address)
request = "https://maps.googleapis.com/maps/api/geocode/json?address=%s&key=%s" % (address, YOUR_API_KEY)
response = urllib.request.urlopen(request)
data = json.loads(response.read().decode('utf8'))
if data['status'] == 'OK':
lat = data['results'][0]['geometry']['location']['lat']
lng = data['results'][0]['geometry']['location']['lng']
return Decimal(lat), Decimal(lng)
For your code to work, add the following lines to the top of your python file:
import urllib
import json
from decimal import Decimal
Let’s break down this code…
def geocode(address):
We can see that this method takes in a string called address which is formatted like a normal address (for example: “180 Main Street, Andover, MA 01810”).
address = urllib.parse.quote_plus(address)
urllib.parse.quote.plus(address) is a handy method from the urllib python package that simply replaces each space in a string with a +. After calling this method, our example address becomes: 180+Main+Street,+Andover,+MA+01810
Now we construct the request url by inserting the edited address and your API key:
request = "https://maps.googleapis.com/maps/api/geocode/json?address=%s&key=%s" % (address, YOUR_API_KEY)
Next we load the JSON data using methods from the urllib and json packages. The method json.loads returns a dictionary from which we can extract our latitude and longitude:
response = urllib.request.urlopen(request)
data = json.loads(response.read().decode('utf8'))
If all our data is properly loaded (i.e. the 'status' is 'OK'), we can find the latitude and longitude in the data dictionary and return them as Decimals:
if data['status'] == 'OK':
lat = data['results'][0]['geometry']['location']['lat']
lng = data['results'][0]['geometry']['location']['lng']
return Decimal(lat), Decimal(lng)