River Quaggy meets Prime Meridian (31st May 2011)

River Quaggy meets Prime Meridian (31st May 2011)

But where exactly?

An epic 8-stage trek along the Meridian Line from Greenwich Peninsula to Peacehaven, Sussex, got underway on Saturday 7th May.

Researched and led by master route plotter and QWAG member, Ralph Palfrey, the first 8.7mile leg follows the Line, with its rich mix of Meridian markers, from the O2 to the bottom of Bromley Hill.

Conveniently, the Meridian passes through Manor Park, Lee. No marker here unfortunately, but some of the 33 or so walkers co-operatively held up a rope to indicate its approximate position.

Prime Meridian

A little southward, the Meridian crosses the River Quaggy – apparently just outside the park boundary but in sight of, the new bridge that will eventually link the park to Longhurst Road.

It would be interesting and educational to mark the exact spot on a wall here. But where is it? Meridian indicators are given on the margins of the Ordnance Survey (OS) Explorer map of the area (Sheet 161). The edition issued to celebrate the Millennium, actually marks the line. But its 0.6 mm width, on a scale of 1: 25 000, represents some 15 metres on the ground. And unfortunately, neither the meridian nor meridian indicators are given on larger scale OS maps.

The red rope marks the approximate position of the Prime Meridian just inside the main entrance of Manor Park - oops, checking the map seems we should have been a few metres back

The red rope marks the approximate position of the Prime Meridian just inside the main entrance of Manor Park – oops, checking the map seems we should have been a few metres back

 

Prime Meridian

Another problem – the meridian marked by the Ordnance Survey is not the Prime Meridian. The OS still uses the meridian that was current at the Observatory during the early years of the Survey in the 18th century, namely James Bradley’s, which is 5.9 metres (19 feet or so) west of the one adopted by the world in 1884. So, depending on latitude, the Prime Meridian is always to be found a little to the east. At Manor Park, the distance will be fractionally more than 5.9 metres.

The Prime Meridian crosses the Quaggy somewhere here, probably a little beyond the park boundary

The Prime Meridian crosses the Quaggy somewhere here, probably a little beyond the park boundary

 

GPS

The probable answer is a GPS (Global Positioning System) receiver. But if you stand on the Prime Meridian at the Royal Observatory, the reading is 0° 00′ 4.5″. Reading 0° 00′ 00″ is shown some 100 metres eastward. This anomaly is insurmountable it seems – a technical problem due to satellite positioning, necessary computer modelling and irregularities in the Earth’s shape.

So borrow a super duper GPS receiver and wade about in the Quaggy till you get a longitude reading of 0° 00′ 4.5″. Is that the problem solved? Expert advice welcome.

For further information on Ralph’s Greenwich Meridian Line Green Merlin) walk, contact him at 020 8460 7215 or rj.palfrey@btinternet.com

Skills

Posted on

8th April 2015

Make a splash without getting wet!