Find County name for a Lat/Long

问题

I'm trying to find a webservice that will allow me to get a County name (not Country) for a specific Lat/Long. I would be performing the lookup within a server application (likely a Java application). It doesn't have a be a webservice if there is some library out there I suppose, but I would like up-to-date information. I have looked around quite a bit for an API that supports this, but so far I haven't been able to find one that works. I have tried the Yahoo APIs like so:

http://where.yahooapis.com/geocode?q=39.76144296429947,%20-104.8011589050293

But it doesn't populate the address information. I've tried with some of the "flags" options there too to no avail.

I've also looked around at Googles APIs as well, but I've read multiple places that they don't populate the County.

So does anyone know of any APIs that will take a Lat/Long and return the County associated with that location? And if you have any examples, that would be great.

I'd also like to know which APIs allow for use in a commercial application. A lot of the data I've found says that you can't use the data to make money. I might be reading those wrong, but I'm looking to build a service that I'd likely charge for that would use this data. So I'd need options. Maybe free services while I'm exploring options, and pay services down the road.

回答1:

Just for completeness, I found another API to get this data that is quite simple, so I thought I'd share.

https://geo.fcc.gov/api/census/

The FCC provides an Block API for exactly this problem and it uses census data to perform the look up.

Their usage limit policy is (From developer@fcc.gov)

We do not have any usage limits for the block conversion API, but we do ask that you try to spread out your requests over time if you can.

回答2:

Google does populate the county for your example,

http://maps.googleapis.com/maps/api/geocode/json?latlng=39.76144296429947,-104.8011589050293&sensor=false

In the response, look under the key address_components which contains this object representing "Adams" county,

{
    long_name: "Adams"
    short_name: "Adams"
    -types: [
        "administrative_area_level_2"
        "political"
    ]
}

Here's from the Geocoding API's docs,

administrative_area_level_2 indicates a second-order civil entity below the country level. Within the United States, these administrative levels are counties. Not all nations exhibit these administrative levels.

回答3:

You may want to have look at Tiger data and see if it has polygons containing the county name in an attribute. If it does the Java Geotools API lets you work with this data. You will be performing point in polygon queries for the county polygons followed by a feature attribute look-up.

回答4:

Another option:

• Download the cities database from http://download.geonames.org/export/dump/
• Add each city as a lat/long -> Country mapping to a spatial index such as an R-Tree (some DBs also have the functionality)
• Use nearest-neighbour search to find the country corresponding to the closest human settlement for any given point

Advantages:

• Does not depend on aa external server to be available
• Much faster (easily does thousands of lookups per second)

Disadvantages:

• May give wrong answers close to borders, especially in sparsely populated areas

回答5:

Maybe this is a great solution.It is in a json format.I always use this in my projects.

http://maps.google.com/maps/geo?ll=10.345561,123.896932

And simply extract the information using php.

$x = file_get_contents("http://maps.google.com/maps/geo?ll=10.345561,123.896932");

$j_decodex = json_decode($x);

print_r($j_decodex);

来源：https://stackoverflow.com/questions/5864601/find-county-name-for-a-lat-long