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Simple Geo DIY
Calculate the distance
along a latitude and
derive travel time & intervals
• “Saw in” the new millennium 20 years ago on the south bank of the
Thames by the London Waterloo Bridge
• Barges were set mid-river at regular intervals to set off as midnight
passed those exact locations from Greenwich Millennium Dome to
the east, to Vauxhall Bridge to the (south)west
Q: how far were barges spaced to set off a second apart each,
and how long did it take to fire them off from beginning to end?
• London lies at roughly 51° N lat.
• Let’s simplify to a straight E-W line
• reasonable from Greenwich to Windsor
• though river does wind, ergo simplification
• What distance does Earth rotate per second?
• calculate the circumference along that latitude
• divide by 24 hr. x 60 min. x 60 sec. = 86,400 sec.
[picture c/o Dr. Anna Kristalli]
51° N lat.
• Measure along parallel at that latitude
• Go to Computing distances between
latitude and longitude in one step
• Enter 51° lat. twice, and 0° then 180°
long. as at right
• Read distances, and double them to get
the full circumference
• Divide by the number in the prev. slide
• 17,398 km. / 86,400 s. = 201 m. in 1 s.
Note on distances
• Along-latitude from Greenwich
Millennium Dome to Vauxhall Bridge
3.7 km. on Google Maps (right top)
• Along the river that becomes 11 km.
• The 200 m barge separation is along
the latitude (straight black line at right)
not the river (crooked black line)
• So barges were aligned according to
EW measures projected along the river
How many barges, and how long did it take?
• That distance divided by the interval between barges is the number of
• 3,700 m. / 200 m. = 18 barges
• And at 1 sec. interval between barges launching the fireworks, that is
approximately 18 sec. for the entire procession up the River Thames:
• 18 barges / (1 barge / sec.) = 18 sec.
• The Independent predicted in July 1999 that it would last 10.8 sec.,
although little other info is available on that went dubbed “River of
Fireworks” headlined by none other than Bob Geldof
Latitude 51° N
Per second Earth
Number of barges 18
Duration 18 sec.
(10.8 in the press)
Fireworks barges set off every second from
Greenwich to Vauxhall up the Thames as midnight
passed them to usher in the new millennium
More DIY map-making here:
Background Thames Path East