If you can research (or estimate) the coordinates of the navaids and intersections that define your local airways, it's relatively simple to define a series of 10nm wide rectangular chunks of airspace which, when combined, will produce an airway on the map. Having said that, in the UK at least there are no upper airway edges as such, only centrelines, since all upper airspace is controlled airspace - I don't know if it's the same in Nigeria.