Mongoose JS Schema methods error

gistfile1.js

/**
 * Module dependencies.
 */

var express = require('express');
var mongoose = require('mongoose');
var fs = require('fs');
var Schema = mongoose.Schema;
var db = mongoose.connect('mongodb://localhost/myapp');

// Schemas

var UserSchema = new Schema({
    first_name:{type:String,required:true},
    last_name:{type:String,required:true},
    email:{type:String,required:true,index:{unique:true}},
    loc:{lng:Number,lat:Number}

});

UserSchema.index({loc:'2d'});

UserSchema.method('findNearbyMatches',function(lng,lat,cb) {
    return this.find({loc:{$near:[lng,lat],$maxDistance:5}},cb);   //<--- ERROR accessing "this", no find() method. SEE ERROR BELOW
});


// Set up models
var User = mongoose.model('User',UserSchema);

app.get('/localmatches/:lng/:lat',requireAuth,function(req,res){
    var user = new User();
    user.findNearbyMatches(req.params.lng,req.params.lat,function(err,users){
        res.contentType('application/json');
        
        var result = {status:'ok',message:'',users:users};
        
        res.send(result);
    })

});

/*
TypeError: Object #<model> has no method 'find'
    at model.findNearbyMatches
*/