Longest Walks in New Zealand

How far can you (theoretically) walk in a straight line, without crossing a sealed road or a body of water?

Inspired by a similar map from Ordnance Survey, I used LINZ Topo50 data to investigate the longest straight lines in New Zealand. Restricted to not crossing sealed roads or bodies of water, the longest theoretical walks are 156km in the North Island, and 258km in the South Island.

The line calculated by OS for the UK (79km through the Cairngorms in Scotland) was successfully followed on foot by a couple in August 2021. Suggesting they try these NZ lines next, a bit of discussion on Twitter led to suggestions that there might be slightly longer lines achievable if the ‘sealed road’ constraint was avoided by either crossing the Milford Sound Highway (SH94) on top of the Homer Tunnel, or crossing the West Coast Road/Otira Highway (SH73) by passing under the Otira Viaduct. Due to the second constraint of not crossing any lake, neither of these options create a line longer than the 258km shown on this map.