It the Toughbook doesn't have an external GPS antenna connector, your options are a bit limited, the built-in antenna needs to be able to present the biggest footprint to the sky, so if that green object in your picture is the antenna, I would guess you would get the best signal when the lid of the Toughbook is closed, but that does make looking at the screen a bit difficult. If you have any software on the Toughbook that displays GPS satellite signal strength, you could do some tests with the lid open (i.e. normal for viewing) and with it horizontal (difficult to view). If the signal figures are better with the lid closed, I would keep it like that most of the time and just open the Toughbook for viewing. It is possible that they use the edge of the 'green object', so the strongest signal is obtained when the lid is open anyway, in which case, the only way to increase the signal would be to have an active external antenna feeding the built-in one