Borough boundaries

How accurate are the borough boundaries lines - e.g between Camden and Haringey - as they don’t appear to be the same as Council ones (e.g. council middle of road, OpenStreetMap side of road in some places).

They should be pretty accurate, as they are sourced from Ordnance Survey who get them from the responsible authorities. The definitive boundary is a line on a map, which might have coincided with the centre line of a road or watercourse when it was first digitised. If the road is subsequently realigned for whatever reason, that does not change the legal location of the boundary.

Also, remember that aerial imagery is subject to all kinds of errors and distortions. Imagery is often used to align roads, but the admin boundary geometries are often obtained directly from a digital source so they will (should) be close to accurate, to within a metre or so.

The definitive maps of boundaries are held at a very large scale, and you can see the line wandering about all over the place, e.g. from the middle of the pavement to the gutter.

If you look at the detailed maps in this document (concerning a boundary change) you can see clearly how boundaries sometimes follow the edge of a road and not the centre line. I have seen more detailed maps than this…,-havering-lb,-thurrock-district-in-essex-county-and-dartford-borough-in-kent-county.pdf