title: ElasticSearch QueryParsingException failed to find geo_point field
body: <p>Trying to build search as follows:</p>
  
  <pre><code>{
    "query": {
      "filtered": {
        "query": {
          "match_all": {}
        },
        "filter": {
          "geo_distance": {
            "distance": "50km",
            "coordinates": {
              "lat": 52.5234051,
              "lon": 4.113999
            }
          }
        }
      }
    }
  }
  </code></pre>
  
  <p>where <em>coordinates</em> is of type <em>'geo_point'</em>.</p>
  
  <p>But when I try to run this query, the elasticsearch.log pops up with an error: 
  [locations] failed to find geo_point field [coordinates]</p>
  
  <p><strong>Edit:</strong></p>
  
  <p>This is part of the /locations/location/_mapping:</p>
  
  <pre><code>{
    "locations": {
    "mappings": {
    "location": {
    "properties": {
      ...
      "coordinates": {
        "properties": {
          "lat": {
            "type": "string"
           },
          "lon": {
            "type": "string"
          }
        }
      },
     ...
   }
  }
  </code></pre>
  
  <p>Any ideas what is wrong here?</p>