Access posted json data from ajax in rails controller

I have made an ajax post request for json data and I want to access that data in the rails controller so how can I access the data.

Here is how I posted the data using ajax

jQuery.ajax({
          url: 'main/getlocation',
          data: "{latitude:" + latitude + ",longitude:" + longitude + "}",
          dataType: 'json',
          type: "POST",
          success: function(data) {
            alert("Successful");
          },
          failure: function() {
            alert("Unsuccessful");
          }
        }); 

How can I access the latitude and longitude data from the rails controller. I cannot access the data using the normal params[:latitude] and params[:longitude]. What should I use?