Ben,
See my answers:
1) The projection used for Google Map is Spherical Mercator as you can see in the Spatial Reference web site spatial-reference.org/ref/sr-org/6627/
In Map Suite, this is ManagedProj4Projection.GetGoogleMapParametersString(). But, if you are only displaying a GoogleMapsOverlay, you need to set the MapUnit of the map to meters because this is the unit used for that projection.
2) To convert from Decimal Degrees (Lat/Long or WGS84), you need to use ConvertToExternalProjection function of ManagedProj4Projection.
To recap everything, please, look at the code below where I do something very simple. I have a GoogleMapsOverlay and I display a point after converting it from decimal degrees to Spherical Mercator (Google Map projection).
I also suggest you look at some Code Community samples that deals with projection issues and Background Maps (Google, Bing etc)
wiki.thinkgeo.com/wiki/Map_Suite_Wp...c)_Samples
wiki.thinkgeo.com/wiki/Map_Suite_Wp...on_Samples
wpfMap1.MapUnit = GeographyUnit.Meter;
wpfMap1.CurrentExtent = new RectangleShape(-14180662, 5547256, -7832569, 1777465);
GoogleMapsOverlay googleMapsOverlay = new GoogleMapsOverlay();
wpfMap1.Overlays.Add(googleMapsOverlay);
ManagedProj4Projection proj4 = new ManagedProj4Projection();
proj4.InternalProjectionParameters = ManagedProj4Projection.GetWgs84ParametersString();
proj4.ExternalProjectionParameters = ManagedProj4Projection.GetGoogleMapParametersString();
double Longitude = -96.80;
double Latitude = 33.50;
proj4.Open();
Vertex googleMapVertex = proj4.ConvertToExternalProjection(Longitude, Latitude);
proj4.Close();
InMemoryFeatureLayer inMemoryFeatureLayer = new InMemoryFeatureLayer();
inMemoryFeatureLayer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = PointStyles.CreateSimpleCircleStyle(GeoColor.StandardColors.Red, 12);
inMemoryFeatureLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
inMemoryFeatureLayer.InternalFeatures.Add(new Feature(googleMapVertex));
LayerOverlay dynamicOverlay = new LayerOverlay();
dynamicOverlay.Layers.Add("PointsLayer",inMemoryFeatureLayer);
wpfMap1.Overlays.Add("DynamicOverlay", dynamicOverlay);
wpfMap1.Refresh();