Long post so forgive me :)

Basically i'm working upon a 7.7.8 new build where I want to grab the users lat/long and pass through to a partial view to render results when they visit the page based upon their location. Straight forward enough. However to do this I need to grab the lat/long before the results are loaded, pass through to a controller, initialise a partial view and return that result back to the browser.

So what i've got is the following code/logic.

// Ajax call:
var postData = { Lat: 53.481091, Long: -2.2373998, NodeId: 1055 };
        $.ajax({
            url: '/umbraco/surface/GridSurface/GetFilteredGrid',
            type: "POST",
            cache: false,
            data: JSON.stringify(postData),
            dataType: "json",
            contentType: 'application/json; charset=utf-8',
            error: function (data) {
            },
            success: function (data) {
                // do something with data
            }
        });


// surface controller:
using System.Globalization;
using System.Web.Mvc;
using Models;
using Umbraco.Web.Mvc;
namespace MyControllers
{
    public class GridSurfaceController : SurfaceController
    {
        [HttpPost]
        public PartialViewResult GetFilteredGrid(Location data)
        {
            //create a RenderModel based on some content ID
            var model = new PosViewModel(Umbraco.TypedContent(data.NodeId), CultureInfo.CurrentUICulture)
            {
                Lat = data.Lat,
                Long = data.Long
            };

            return PartialView("~/views/partials/GridLoader.cshtml", model);
        }
    }
}

Partial view being called has the inherit:

@inherits UmbracoViewPage<Models.PosViewModel>

Then does some rendering of map based upon passed in lat/long

// Model:
public class PosViewModel : RenderModel
    {
        public PosViewModel(IPublishedContent content) : base (content) { }
        public PosViewModel() : this(new UmbracoHelper(UmbracoContext.Current).TypedContent(UmbracoContext.Current.PageId)) { }
        public PosViewModel(IPublishedContent content, CultureInfo culture) : base(content, culture) { }
        public double Lat { get; set; }
        public double Long { get; set; }
    }

Error is thrown initialising this PosViewModel in line base (content, culture) - says content is null however culture coming through fine!! Why would this be when i'm using Umbraco.TypedContent to pass a copy of that object in based upon the current page id.

Now I now I should normally use CurrentPage to init my model, however as posting from Ajax I don't have a page. This is why I pass in the nodeId and use Umbraco.TypedContent to sort this out for me, object is clearly valid before passing into the constructor, why does the model not allow it and state it's null? Umbraco bug? ModelsBuilder is set to LiveDll if that has any bearing on things.

Any ideas how to sort this annoying problem out?