Halfway to the Pole

Introduction

Nova Scotia straddles 45N, and there is a tourist spot named Mastodon Ridge Park that claims to be halfway between the pole and the equator. But it is not at 45N, because that’s the halfway point for a spherical earth, not the flattened earth on which we live.

So, is it really at this halfway point? The following R code is an attempt to answer that question.

library(oce)
L <- geodDist(0, 0, 0, 90)
uniroot(\(lat) geodDist(0, 0, 0, lat) - L/2, c(0, 90))$root

This code indicates that the halfway point is at 45.14432N, which is about 16 km from 45N.

The Mastodon Ridge website shows a letter (dated 1952, when someone might be referred to as a ‘field man’) that indicates that the halfway point is 45 degrees 8 minutes, 50 seconds. Converted to decimal, that is 45.14444, which is very close to the value from the R code given above. (The difference, 45.14444 - 45.14432, is just 14 metres!)

I have not gone to this place to check the actual location of the marker, but google maps tells me it is about 200 metres further north on the highway, just about at the bridge over the Stewiacke River. That’s about a 2 minute stroll away from the Mastodon Ridge buildings. If a reader happens to take a photo of the position marker (which I hope is still there), I’d be happy to post it on this blog!