How to Perform Geospatial Queries in Mongoose

I am using mongoose with NodeJS and have the following model:

var Post = new Schema({
  ...
  location: [Number, Number],
  ...
});
Post.index({ location: '2d' });
Post.set('autoIndex', false);
module.exports = mongoose.model('Post', Post);

      

        
        
        
      

    

When the user makes a query for all posts, they can add an optional beside query parameter to find posts with locations within a given radius of about

GET /api/1.0/posts?near=12.3244,-1.23244

      

        
        
        
      

    

For this to work, I do the following:

if(req.query.near) {
  var loc = req.query.near.split(',');
  var area = { center: loc, radius: 10, unique: true, spherical: true };

  if(loc.length === 2) {
    query
      .where('location')
      .within()
      .circle(area);
  }
}

      

        
        
        
      

    

And then I execute the request. I did it using this mongoose documentation

I have 3 questions:

• What is the unit of radius, miles or kilometers?
• Divide radius by 3963.2 how is done here (equatorial radius of earth), or mongoose handle, what?
• What does unique mean? (top) and spherical? I suppose spherical means use mongo $ centerSphere as opposed to $ center, right?

Any help would be appreciated, especially questions 2 and 1 Thank you :)