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G0SYR > GOOGLE 09.03.08 15:00l 125 Lines 5858 Bytes #999 (0) @ WW
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Subj: Re: Strange
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Hi Bob and all
On Sun, 9 Mar 2008 04:31:00 +0000,
vk6be%vk2tv.#mnc.nsw.aus.oc@gb7cip.ampr.org wrote:
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> Subject: Strange
> Date: Sun, 9 Mar 2008 04:31:00 +0000
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> From: VK6BE@VK2TV.#MNC.NSW.AUS.OC
> To : GOOGLE@WW
>
>
> I have been playing with Google Earth. There are some very strange
> features of the program. Some parts of Albany are quite accurate and
> fairly well up to date but others are hopelessly inaccurate and show some
> features as they were 40 years ago. Also I can't understand how some large
> detail can be missing from the pictures.
>
> As an example there is a large cemetery and crematorium just outside the
> city over the road from a suburb called Bayonet Head, easily found on the
> pictures.
>
> The patch of ground where the cemetery is situated is easy to see as also
> is the parking area as it was about 40 years ago, incomplete and gravel
> and even with a couple of cars parked. There is no sign of the cemetery
> itself, no gravestones and monuments, no crematorium building. Yje
> cemetery was estab;lished about 40 years ago, maybe a few years earlier
> than that when the cemetery in town was becoming too big for the space -
> it was over 100 years old.
>
> I found my daughters' house which is 6 km outside the city area. The house
> and outbuildings are there, even the top of the septic tank, but no
> garden.
>
> Please see if you can refrain from silly comments at my expense, Warren. I
> am telling you as I see it. There are some very strange features of the
> program.
> Bob VK6BE.
It's hard for us to comment as you are not very precise with your
directions but if I search for Bayonet Head Albany I see the suburb and
my best guess at the meaning of 'over the road' is traveling along
Bayonet Head road and Evans Street I cross over Lower King Road to find
a large cemetery and cemetery building at
34 deg 58 mins 52.81 secs South 117 deg 55 mins 09.46 secs East
Now this may be another large cemetery completely but if you can give us
some more accurate information as to its location we can take a look and see
if WE can find it :-)
Like Ray VK2TV I'm a bit of a mapaholic and he makes the important
distinction between accuracy and currency all of my paper maps are no where
near as current as Google Earth but that just means you need some common
sense when using them. It makes them no less useful and no less interesting.
If you consider how Google earth constructs its database it is pretty
obvious it is a mosaic of photographs merged together, some probably
lower resolution satellite images for some areas and other higher resolution
aerial photographs in others. These have been shot at times when cloud cover
is favorable but are shot at all sorts of different times of day with
different lighting conditions so sometimes objects stand out when cast
shadows are favorable other when lit from more overhead are less distinct.
Often objects are not photographed from precisely above so the side of tall
objects such as TV towers can be seen.
Bob is correct in that there are interesting anomalies when you consider
that the 3D view provided by Google earth is a combination of a 2
dimensional mosaic photograph and height terrain data this gives some
need for compromise in some areas.
One interesting problem area are coastal regions with vertical cliffs
such as the famous White Cliffs of Dover. Photographed from above the side
of the cliff may not be visible yet the terrain data would show around 600
ft drop. When approaching the coast in the flight simulator there would be
no
real photographic image to display on the cliff face.
I think this is handled differently depending on how much effort has been
put into processing the data. At the cliffs of Dover it seems they have
suppressed the terrain data so the cliff heights have been reduced to sea
level so it appears as you fly in from the sea you just see a flat beach.
Take a look by zooming in on the Shakespeare Cliff just west of Dover in the
UK at
51 deg 06 mins 39.00 secs North 1 deg 17 mins 36.00 secs East
and change your height of viewing down towards sea level and you will see no
cliff ! Yet the more undulating terrain further inland is visible. Even
though in this case the white chalk of Shakespeare cliff is not actually
vertical and is clearly visible from above on the 2 D photograph
Another interesting anomaly can be seen in the Lake district in the North
West of England. Just search for Wast Water, one of the lakes. If you fly
over it, with Terrain switched on, you will see that the surface of the
lake is not flat! Obviously height data from some source has been included,
showing some terrain data for the normal bed of the lake which has the
strange effect of showing the water apparently covering the lower slopes of
the surrounding hills :-)
I would guess that most of Google earth's photographic data was photographed
within the last five years. I doubt any of it was compiled from photographs
over 40 years old but perhaps Bob will prove me wrong.
--
73 de Bryan
AX25 mail: G0SYR@GB7CIP.#32.GBR.EU
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