Geosurvey from orbit doesn't need that a body is a colony. So, why not the same for ground geosurvey?
Please, remove the need that a body is declared as a colony, to unload geosurv troops on it.
Since ground units require a population to be at (unless on a ship), I think the best solution here would be to have an order to create a colony and unload ground units there.
Actually, that would be nice to have for all of the unload orders, if a body is the target of the order create a colony (of the unloaded species for a colony ship, otherwise of the primary species is probably fine in most cases). Simply modifying existing unload orders to work this way for non-population targets instead of adding new orders would avoid cluttering the interface as well.