So, just finished reading those books. Surprsingly, neither one (Galaxy Guide 1: A New Hope nor the Deathstar source book) have anything to say about which trench was attacked during the Battle of Yavin.
The Deathstar sourcebook gives us some, propably not canon anymore, details about the Deathstar, e.g. it being divided into 24 sections, 12 per hemisphere, that there are the equatorial, and mid-hemisphere (one each north and south) and polar trenches (again, one each north and south) running parallel to the equator. Or there being trenches running between those 12 sections per hemisphere. But nothing about which trench was attacked. Maybe the Alliance and the New Republic have yet to de-classify that information.
