[Geotools-gt2-users] How to add a WGS84 based layer over OSGB36 layers?

[Andrew M. <an...@en...>]

Hello,
I am completely new to Geotools (and also GIS), but I am very 
experienced with Java so it's not all bad news!
I have adapted the SpearfishSample to read in dem data using the 
ArcGridDataSource.
I then read in a shape file which has the OSGB36 grid lines at 5km 
resolution.

This works perfectly and is very encouraging!

But now I want to display a marker at a specific location.
The location is specified by the user as OSGB36 coordinates.

I have adapted the code from the 'How to create a Custom Map Layer' to 
make a layer with a symbol on it.
The example code uses WGS84, so I convert the location from the OSGB36 
reference to WGS84 using a Helmert Transformation. And specify the 
coordinates of the location on this new Layer.

I then add the layer to the map, and the marker is displayed in the 
bottom left hand corner.
I presume this is because the map is expecting the location to be 
specified in the OSBG36 form, and doesn't know where to place the marker.

Obviously I am going about this in the wrong way, can anyone point me in 
the right direction?
 
Thanks in advance

Andrew