the most likely orientation is (assuming BHG made the compass directions the sides of the map rather than the corners, and that bases are in the northern hemisphere) Alliance Gate = North, River = south. The other option is Embassy = south.
Looking at the shadow from a redoubt, it is pointing somewhere between the mountain and the Alliance gate, but more in the direction of the gate. It is also quite a short shadow, suggesting sun is fairly high in the sky and it is close to noon. If the redoubt were a sundial, it would be reading around 10:30 am, and the river must be south.
The other possibility (Embassy = south) would mean that it is about 4:30 pm, but then the shadow would be much longer.