I also have aphantasia but can navigate just fine. I read a comment on here once from someone with aphantasia that couldn't navigate in the real world, but they worked in network admin and knew that layout just fine (knew where everything routed and what it connected to etc). I pondered that if they could remember cable routes, why don't they apply the same mental map to roads? Roads are fixed and have a beginning and end too! But they reckon they could not. So it's a strange problem.