"Richard J." typed


John Rowland wrote:
They've replaced the photograph of London with a newer one. It was
taken just after dawn in midwinter, so there are shadows of naked
trees stretched across everything, making it nearly useless!

It can't be just after dawn, not everywhere anyway. Shadows in central
London (e.g. Nelson's Column) indicate that it's late morning, roughly
around 11:00. There's an event of some sort in Trafalgar Square. From
the works going on in Devonshire Road, Chiswick, I would say it was
around January or February this year. Colin says it must be a Sunday
morning. Between us on this NG, we ought to be able to pin it down to a
date.

Looking at the area close to my parents' place in NW11, the sun is in
the south-southwest, making it about 1-2pm, the shadows are long, and
the silver birch in their front garden has been removed.

I note my abode is *just* outside the area of the updated image, which
is at the NW9/HA8 frontier.

--
Helen D. Vecht:
Edgware.

I still went to choir at the time, so it would be before summer 2005
(possibly winter 2004-5).

Wasn't that the Eastbound platform?

They did Eastbound first, then Westbound. The Metronet website has a press
release dated December 2004 to say that the Westbound work would be 9th July
to 31 Dec 2005, but I think the platform was opened a little early and then
the landscaping that they're doing in the photo was done later.

Another possibility of finding a date is the old Victoria Hall Adult
Education centre in Ruislip Manor (big building facing the carpark directly
south of the tube station - http://tinyurl.com/jv5dr) which is there in the
photo, but was flattened earlier this year. Planning permission was granted
for the redevelopment in December 2005 and I know it was flattened by July
2006, but that doesn't narrow it down much does it!

Must've been a weekend though, the carparks at the large shops in South
Ruislip are full. Check the monster tree shadows outside Wickes at
http://tinyurl.com/zocoh !

Well, if you take a look at St. Paul's cathedral, there is a very good
shadow to work with.

In marine navigation, you know what day/time it is, and you calculate where
you are based on where the sun is. With this situation, you know where you
are at, so you solve for the other side of the equation.

First, the latitude here is about 51D30M49.90S

You can draw a line straight north of the dome, and calculate the time of
the exposure that way, like a sundial. some folks have responded about that
already.

Then, you can triangulate the length of the shadow, and the known height of
the dome. It's a bit uphill as you go north, I seem to recall, which may
shorten the shadow, so that should be taken into consideration.

With this, you will get the angle of the sun (declination). You now have a
known latitude, pretty close time of day, and (also pretty close) angle of
the sun.

With all of that, and this:

http://rds.yahoo.com/_ylt=A0geups.AShFJJgAg11XNyoA;_ylu=X3oDMTE2YW83ZnI 3BGNvbG8DZQRsA1dTMQRwb3MDMwRzZWMDc3IEdnRpZANNMDAxX zc0/SIG=13gfeq4il/EXP=1160336062/**http%3a//www.bath.ac.uk/%7eabsmaw/Facade/sunlight_01.pdf%23search='sun%2520position%2520glo be'

-that should get you to when the photo was taken.

Since I have to get to the gym yet today before going to some event I have
be at later, we'll let somebody else do the maths.

-RED





around January or February this year. Colin says it must be a Sunday

Ralph Diehl wrote:
Well, if you take a look at St. Paul's cathedral, there is a very
good shadow to work with.

Except that you can't see how long it is, because it ends somewhere in
Newgate Street which is in shadow from nearer buildings, and also
there's a join there between two photographs.

--
Richard J.
(to e-mail me, swap uk and yon in address)

Yes, I abandoned that object for about the same reason.

I'm playinng with the shadow of the tate modern chimney now, it's a bunch
clearer. Somebody said it was about 11am, it's not quite 11:30am according
to the angle I got.

I'm trying to remember the distance down to the river (how many feet lower
the river level is from the base of chimney), it's been nearly a year since
I was last there. (I live about 6K miles away from it)


RED



Except that you can't see how long it is, because it ends somewhere in

Ralph Diehl wrote:
Yes, I abandoned that object for about the same reason.

I'm playinng with the shadow of the tate modern chimney now, it's a
bunch clearer. Somebody said it was about 11am, it's not quite
11:30am according to the angle I got.

I'm trying to remember the distance down to the river (how many
feet lower the river level is from the base of chimney), it's been
nearly a year since I was last there. (I live about 6K miles away
from it)

The river level varies by up to 7 metres depending on the state of the
tide, so that may not be a good shadow to choose.
--
Richard J.
(to e-mail me, swap uk and yon in address)

On Sun, 8 Oct 2006, Richard J. wrote:

Ralph Diehl wrote:

Yes, I abandoned that object for about the same reason.

I'm playinng with the shadow of the tate modern chimney now, it's a
bunch clearer.

The chimneys of Battersea Power Station are also very good.

Somebody said it was about 11am, it's not quite 11:30am according to
the angle I got.

I'm trying to remember the distance down to the river (how many
feet lower the river level is from the base of chimney), it's been
nearly a year since I was last there. (I live about 6K miles away
from it)

The river level varies by up to 7 metres depending on the state of the
tide, so that may not be a good shadow to choose.

Ah, but if we can deduce the height of the tide from a feature on the
Thames, we can correct for that. And we'd have a double-check on the date
and time via the tide tables. If you look at the Thames barrier or the
Woolwich ferry piers, you can see the tide is definitely on the flood, and
i'd say coming in at quite a rate, which would mean it was something like
halfway between low and high tide.

This stepped bank at the mouth of Barking Creek:

http://maps.google.co.uk/maps?z=19&l...6,0.096506&t=k

Could be useful, if we had some way of calibrating it! The mudflats at
Erith would also do.

Alternatively, how about the monumenty thing in Regent's Park:

http://maps.google.co.uk/maps?z=19&l...,-0.150633&t=k

Too short to measure accurately?

tom

--
When you mentioned INSERT-MIND-INPUT ... did they look at you like this?

Then, you can triangulate the length of the shadow, and the known height
of the dome. It's a bit uphill as you go north, I seem to recall, which
may shorten the shadow, so that should be taken into consideration.

With this, you will get the angle of the sun (declination). You now have a
known latitude, pretty close time of day, and (also pretty close) angle of
the sun.

That's all way beyond my abilities!

I could read a sundial though, I'm sure... is this one?
http://tinyurl.com/rjjs2

Helen Deborah Vecht wrote:
I still went to choir at the time, so it would be before summer 2005
(possibly winter 2004-5).

When I had a look at google maps last I noticed that the Load of Hay
pub in Brent Street was still there with its car park.

That pub was demolished some time ago and there are now flats there. I
can't remember the exact dates though.

Tom Anderson wrote:
On Sun, 8 Oct 2006, Richard J. wrote:

Ralph Diehl wrote:

Yes, I abandoned that object for about the same reason.

I'm playinng with the shadow of the tate modern chimney now, it's
a bunch clearer.

The chimneys of Battersea Power Station are also very good.

Somebody said it was about 11am, it's not quite 11:30am according
to the angle I got.

I'm trying to remember the distance down to the river (how many
feet lower the river level is from the base of chimney), it's been
nearly a year since I was last there. (I live about 6K miles away
from it)

The river level varies by up to 7 metres depending on the state of
the tide, so that may not be a good shadow to choose.

Ah, but if we can deduce the height of the tide from a feature on
the Thames, we can correct for that. And we'd have a double-check
on the date and time via the tide tables.

The tide tables won't hwlp much, as they only show the predictions. On
Saturday afternoon (7 Oct) the river was about 0.4 m higher than
predicted at London Bridge, and a metre higher at Richmond.
--
Richard J.
(to e-mail me, swap uk and yon in address)