Magnetic
Glasgow is planned on a grid that is exactly 13 degrees of off the ordance north /south axis. I have speculated that the 13 degrees is because historically the city was set out by surveyors who used a traditional magnetic compass. Magnetic North is again exactly 13 degrees if you are taking a reading in Glasgow. (I.e. Sauchiehall Street, Buchanan Street, Argyle Street are all set out at this angle.)
It was only when I was studying old sailing maps of the West of Scotland that I noticed that the compass rose diagrams on these maps changed direction as you proceeded up the coast due to the magnetic pull in that specific location.
I have checked other cities across the world for this potential connection and can confirm that it is a familar occurence ... if only the Victorians had used the stars.
Anyway ... a recent tower proposal we prepared for Custom House Quay is understood as a vertical manifestation of this interplay between true north and magnetic north as well as being an absolute marker for people in Buchanan Street to continue down to the City's waterfront. Just an idea ...
