Google geocode API returns inconclusive results

Question

For some addresses that I attempt to geocode, google returns inappropriately inconclusive results.

The following is an example, but it is not an isolated incident. The first returned result is the exact match, however google flags it as a "partial_match":

Street address: 16160 Frederick Rd 
City:           Gaithersburg 
State:          MD
Zip code:       20877

Link: http://maps.googleapis.com/maps/api/geocode/json?sensor=false&address=16160%20Frederick%20Rd,+Gaithersburg,+MD,+20877

My issue here is in determining which is the correct match. In this case, the "partial match" flag is not useful because it is set to "true" on all matching results. In this case, I could test for equality on the street address, city, state, and/or zip, however, if there is even a small difference in spelling between what I send google, and what I get as a response, that will not work either. (Example: "Road" vs "Rd").

Am I doing something wrong here? Is there a conclusive way to distinguish the exact match that I am unfamiliar with?

Thanks!

Answer 1

Google does a wonderful job at address approximation. What you're looking for is address verification. SmartyStreets provides an address verification API that is conclusive in it's results. Here's what the SmartyStreets API returns for that address:

Input:

https://api.qualifiedaddress.com/street-address/?street=16160%20Frederick%20Rd&street2=&city=gaithersburg&state=md&zipcode=20877&candidates=10&auth-token=YOUR_AUTHENTICATION_TOKEN_HERE

Output:

[
    {
        "input_index": 0,
        "candidate_index": 0,
        "delivery_line_1": "16160 Frederick Rd",
        "last_line": "Gaithersburg MD 20877-4011",
        "delivery_point_barcode": "208774011604",
        "components": {
            "primary_number": "16160",
            "street_name": "Frederick",
            "street_suffix": "Rd",
            "city_name": "Gaithersburg",
            "state_abbreviation": "MD",
            "zipcode": "20877",
            "plus4_code": "4011",
            "delivery_point": "60",
            "delivery_point_check_digit": "4"
        },
        "metadata": {
            "record_type": "S",
            "county_fips": "24031",
            "county_name": "Montgomery",
            "carrier_route": "C004",
            "congressional_district": "08",
            "latitude": 39.12162,
            "longitude": -77.17619,
            "precision": "Zip9"
        },
        "analysis": {
            "dpv_match_code": "Y",
            "dpv_footnotes": "AABB",
            "dpv_cmra": "N",
            "dpv_vacant": "N",
            "ews_match": false
        }
    }
]

Notice that the "dpv_match_code" is "Y". That's USPS-speak for a verified delivery point--you know that it's a real address at that point. SmartyStreets uses official, current USPS data and is a CASS-Certified software provider.

The API is free for non-profits, educational institutions and low-usage users. Once you've received a result from SmartyStreets you could then geocode it with Google. Full disclosure: I'm a developer at SmartyStreets.

EDIT: Added Latitude/Longitude fields (newly released)