See the details of how to commission a grid at SnakeGrid for your project.

In this case you need to tell us the name of the existing SnakeGrid that you want to merge into, with details of the point where you want the join to occur. This could be a set of coordinates, but it also helps to give a description – “at Claydon Junction”, for example. The new grid will have the same coordinates and orientation as the existing one at the junction, and the coordinates will generally agree within around 2 mm up to 2 km away, allowing through surveys and computations from one grid to the other.

You can only join at one point – you can’t tie into another grid at the far end, or come back into the first one at a different point.