Rhumb Line

So I woke up in the middle of the night wondering whether ‘about 1900 nautical miles’ was really the distance from Steeple Point to Quirpon Island off the northern tip of Newfoundland or whether I had been sloppy in using the Google Earth ruler to measure it. This got me to thinking about rhumb lines.

The Wikipedia definition of Rhumb Line is:

  • “In navigation, a rhumb line . . . is a line crossing all meridians of longitude at the same angle, i.e. a path derived from a defined initial bearing. That is, upon taking an initial bearing, one proceeds along the same bearing, without changing the direction as measured relative to true north.”

My measurement wasn’t “a line crossing all meridians of longitude at the same angle” but a line crossing all meridians of longitude at the same latitude.

There will be a difference in the lengths of these lines. How much longer will depend how far north the lines are drawn, because of the spherical nature of the earth. The question for me was whether the Google Earth ruler measurement differs from other means of measuring the distance.

So, I reviewed the measurements.

Firstly, for my latitude line, I needed to be more accurate in my landfall in Newfoundland.

The coordinates for Steeple Point are: 50 52 34N  004 33 39W

For Cape Bauld Lighthouse on Quirpon Island the northern tip of Newfoundland: 51 38 24N  055 25 36W

If we move 55 miles south as the crow flies, we come to the harbour at Conche – the coordinates  here are: 50 53 09N  55 53 22W – very nearly on the same latitude as Steeple Point.

The Google Earth ruler gives a length from Steeple Point to Conche of 1,915 nautical miles.

I looked for a site that calculates the Rhumb line and came across this one Movable Type Scripts.

Entering the coordinates for Steeple Point and Conche gave me:

  • Distance:            3,536 km (to 4 SF*) – 1,908 nautical miles
  • Initial bearing:     290°02′46″
  • Final bearing:     249°13′06″
  • Midpoint:            53°38′41″N, 030°17′27″W

You will notice that, whereas the distance is fairly accurate, this isn’t strictly a rhumb line because the bearings are not the same.

Best I can do for the moment.

By the way, Conche looks a good place to visit in summer.

Steeple Point

It has been well over a year since I last posted here. There are reasons for this and I will talk about them in time.

But now that I am ready to start again, I find that the title  ‘bill’s boatblog’ does not adequately cover what I want to say.  I want to reflect wider horizons. However, I don’t want to start a new blog – life’s too short.  Hence the new title.

I have changed the font but kept the general layout – there is a lot of historical material that I have posted over the past six or seven years that I would like to keep and one or two readers may find  the book references useful.

WordPress has developed into a much more sophisticated software package since my first timid attempts at posting.  This is a good thing – we all like to move forward. My first thoughts were that more sophistication means more complication – the process taking over the content. In fact, the changes have made it easier to post on this site. I look forward to more posts.

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Steeple Point - standard

I have chosen Steeple Point – a place I have mentioned often. It plays an important part in my story and now that I am moving on from my day job, I want to have a physical base with a long personal connection from which to develop the blog.  I could have used a street we have lived in – Belle Vue or Cavendish Road or South Pallant or Martins Lane  or Clonbern Road or Nayland Rd South or Stockbridge Gardens or Paradise Road or others. Yes, there are more but none have the nautical connection I am looking for. Steeple Point stretches into the sea. I knew this place before I was old enough to know I knew it.

And there’s more. If the Earth were flat and your eye a perfect instrument, you could stand on Steeple Point, look due west, and see, first of all, very slightly to the north, Cape Clear Island and Fastnet Rock and then, on the southern tip of Ireland, Mizen Head , followed by no land at all until Quirpon Island with L’Anse aux Meadows beyond on the very northern tip of Newfoundland some 1,900 nautical miles away. All between is sea and ocean, wide horizons swept by wind and weather,

DSC05589

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I will still talk about the boat, and I still have an eye for Greek fishing boats particularly those in Crete. They will feature, as will the past, especially the trading ketches of North Cornwall and the Bristol Channel. But there will also be occasional notes about what is going on around me as a I age in an increasingly complex world. Like it or not, all our horizons are changing. We need to recognise those changes.