That square white piece is the ceramic antenna for that particular GPS module in that picture.
The ceramic antenna is incorporated into the GPS module that's on your Solo, that picture is not what is installed in your Solo or it would not even acquire satellites without the ceramic antenna.....it' has nothing to do with a compass...
View attachment 8784 This is the stock GPS Module Note the Ceramic antenna? You most likely did not see this when you had the solo apart because it's located on top beneath the cover, you would have to remove the GPS module and turn it around to see it..