How to georeference model in Unity3d?

Hi, I don't know what it is that you are trying to do, so what I'm about to say may not be relevant and for that, I apologise.

Anyway, I am looking at mapping objects with lat and lon coordinates to the surface of a sphere. I took the coordinates from various places around the world from this site (http://www.latlong.net/) so that I could place the objects and see if their positions matched with the texture of the sphere (earth texture).

Note: Unity mesh is not suitable for this... you must get a mesh from blender with the UVs or download one from the web. I used this one: http://tf3dm.com/3d-model/planet-earth-99065.html.

Import the mesh into Unity, and download a texture: http://visibleearth.nasa.gov/view_cat.php?categoryID=1484 I used this one: http://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73909/world.topo.bathy.200412.3x5400x2700.png

To map from Polar (lat lon) coordinates to Cartesian (xyz), you can use this function:

  private Vector3 PolarToCartesian(LatLon polar, float radius)
     {
         var latitude = DegreeToRadian(polar.Latitude);
         var longitude = DegreeToRadian(polar.Longitude);
 
         latitude = 1.570795765134f - latitude; // subtract 90 degrees (in radians)
 
         return new Vector3
         {
             x = (radius)*Mathf.Sin(latitude)*Mathf.Cos(longitude),
             y = (radius)*Mathf.Cos(latitude),
             z = (radius)*Mathf.Sin(latitude)*Mathf.Sin(longitude)
         };
     }

Radius is the radius of the sphere onto which I map the objects.

LatLon is just...

 public class LatLon
 {
     public float Latitude { get; set; }
     public float Longitude { get; set; }
 }

and you need to convert your degrees to Radians:

   private float DegreeToRadian(float input)
     {
         return Mathf.PI * input / 180;
     }

So, for example, you have a sphere with radius 10 and you want to place a game object at based on the coordinates of London: 51.500083, -0.126182.

You can create a new game object like such:

  GameObject item = GameObject.CreatePrimitive(PrimitiveType.Cylinder);
  Vector3 itemPosition = (PolarToCartesian(new LatLon {Latitude = lat,Longitude=  lon},RadiusOfParentSphere));
  item.transform.Translate(itemPosition );
  item.gameObject.GetComponent<Renderer>().material.color = color;

Everything here is based off the fantastic work done by mgear: http://unitycoder.com/blog/2016/03/01/latitude-longitude-position-on-3d-sphere-v2

Note: you may need to rotate your sphere a bit to get the mapped object to align with the texture.

Hope this helps!