CSV geodata into elasticsearch as a geo_point type using logstash

Below is a reproducible example of the problem I am having using to most recent versions of logstash and elasticsearch.

I am using logstash to input geospatial data from a csv into elasticsearch as geo_points.

The CSV looks like the following:

$ head simple_base_map.csv 
"lon","lat"
-1.7841,50.7408
-1.7841,50.7408
-1.78411,50.7408
-1.78412,50.7408
-1.78413,50.7408
-1.78414,50.7408
-1.78415,50.7408
-1.78416,50.7408
-1.78416,50.7408

I have create a mapping template that looks like the following:

$ cat simple_base_map_template.json 
{
  "template": "base_map_template",
  "order":    1,
  "settings": {
    "number_of_shards": 1
  },

      "mappings": {
        "node_points" : {
          "properties" : {
            "location" : { "type" : "geo_point" }
          }
        }
      }
}

and have a logstash config file that looks like the following:

$ cat simple_base_map.conf 
input {
  stdin {}
}

filter {
  csv {
      columns => [
        "lon", "lat"
      ]
  }

  if [lon] == "lon" {
      drop { }
  } else {
      mutate {
          remove_field => [ "message", "host", "@timestamp", "@version"     ]
      }
       mutate {
          convert => { "lon" => "float" }
          convert => { "lat" => "float" }
          }

      mutate {
          rename => {
              "lon" => "[location][lon]"
              "lat" => "[location][lat]"
          }
      }
  }
}

output {
  stdout { codec => dots }
  elasticsearch {
      index => "base_map_simple"
      template => "simple_base_map_template.json"
      document_type => "node_points"
  }
}

I then run the following:

$cat simple_base_map.csv | logstash-2.1.3/bin/logstash -f simple_base_map.conf 
Settings: Default filter workers: 16
Logstash startup completed
....................................................................................................Logstash shutdown completed

However when looking at the index base_map_simple, it suggests the documents would not have a location: geo_point type in it...and rather it would be two doubles of lat and lon.

$ curl -XGET 'localhost:9200/base_map_simple?pretty'
{
  "base_map_simple" : {
    "aliases" : { },
    "mappings" : {
      "node_points" : {
        "properties" : {
          "location" : {
            "properties" : {
              "lat" : {
                "type" : "double"
              },
              "lon" : {
                "type" : "double"
              }
            }
          }
        }
      }
    },
    "settings" : {
      "index" : {
        "creation_date" : "1457355015883",
        "uuid" : "luWGyfB3ToKTObSrbBbcbw",
        "number_of_replicas" : "1",
        "number_of_shards" : "5",
        "version" : {
          "created" : "2020099"
        }
      }
    },
    "warmers" : { }
  }
}

How would i need to change any of the above files to ensure that it goes into elastic search as a geo_point type?

Finally, I would like to be able to carry out a nearest neighbour search on the geo_points by using a command such as the following:

curl -XGET 'localhost:9200/base_map_simple/_search?pretty' -d'
{
    "size": 1,
    "sort": {
   "_geo_distance" : {
       "location" : {
            "lat" : 50,
            "lon" : -1
        },
        "order" : "asc",
        "unit": "m"
   } 
    }
}'

Thanks