Re: Google Earth Plus

In sci.geo.satellite-nav Terry Pinnell <[email hidden]>

Quoted message said:

Thanks, I'd wondered how old the Google images were. (Seems a pity
such key data isn't included or accessible. Or maybe it is?)

For the US, there's a list of dates. For the rest of the world, there is
an indication of where they have hi-res, but no dates.
http://earth.google.com/images_dates.html

Google, 1600 Amphitheatre Parkway, 94043, is at one inch per pixel. It
doesn't seem like it is at that level of detail, but you can see the drop
in resolution as soon as you cross the street, or in the corner of the
parking lot at the upper left of the campus.

On my monitor, high res areas blur at about 900 feet "Eye altitude", but at
the Google Campus, it's clear down to 100 feet. I just can't see what I
thought I would see at that level.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

In message <[email hidden]>, Terry Pinnell
<[email hidden]> writes

Quoted message said:

Nick Hopton <[email hidden]> wrote:

Quoted message said:

Quoted message said:

By the way, the
high-resolution satellite pictures of the area look to be quite recent,
taken in the last 18-months I'll say.

Quoted message said:

Thanks, I'd wondered how old the Google images were. (Seems a pity
such key data isn't included or accessible. Or maybe it is?)

The low resolution ones are certainly a bit older. The land at the
north end of Belfast Harbour shown as enclosed but not dry land was
reclaimed about 3 years ago and the M6 Toll appears to be under
construction.
--
Goalie of the Century

In a recent message <[email hidden]>, Terry
Pinnell <[email hidden]> wrote.

[...]

Quoted message said:

Thanks, I'd wondered how old the Google images were. (Seems a pity
such key data isn't included or accessible. Or maybe it is?)

[...]

Just to mention that even though the high-resolution satellite images
are recent the elevation data isn't. The landform at Dorney has changed
enormously since the elevation data (SRTM, presumably) was gathered, but
Google Earth still reports it as being about 21-metres AOD across the
whole site. Which it was when the elevation data was gathered, but it's
not now.

Regards,
Nick.
--
Nick Hopton and Anne Hopton
Caversham, Reading, England
<[email hidden]>

What does the "DG Coverage 2005", etc., shown in the "layers" table
refer to?

Nick Hopton said:

In a recent message <[email hidden]>, Terry
Pinnell <[email hidden]> wrote.

[...]

Quoted message said:

Thanks, I'd wondered how old the Google images were. (Seems a pity
such key data isn't included or accessible. Or maybe it is?)

[...]

Just to mention that even though the high-resolution satellite images
are recent the elevation data isn't. The landform at Dorney has changed
enormously since the elevation data (SRTM, presumably) was gathered, but
Google Earth still reports it as being about 21-metres AOD across the
whole site. Which it was when the elevation data was gathered, but it's
not now.

Nor does the 'Layer' data seem accurate. For example, railways and
roads see incomplete and displaced from the true positions. Here's an
example from Southern Spain, where the road layer is plainly
incomplete and inaccurate:
http://www.terrypin.dial.pipex.com/Images/GE-LayerErrors1.gif

BTW, S. Spain has a surprisingly high coverage at high resolution. Any
idea why? Hardly a town or village for miles, yet you can see
individual olive trees!

--
Terry, West Sussex, UK

Terry Pinnell said:

. . .
BTW, S. Spain has a surprisingly high coverage at high resolution. Any
idea why? Hardly a town or village for miles, yet you can see
individual olive trees!

you got the point ;-)

Spain has many services at high resolution because of the Agricultural
Subventions from the EU, see <http://sigpac.mapa.es/fega/visor>

just guessing . . .
;-) Anton

The high resolution areas appear to be at random. In SE Spain, the
naval areas at Cartagena are low-res; whilst the flying school at San
Javier is high-res. There have been questions in the Spanish parliament
regarding the high-res areas in Madrid.
Referring to your other posts - it's noticeable that Windsor and
surrounds is low-res, also central London

In sci.geo.satellite-nav Nick Hopton said:

Just to mention that even though the high-resolution satellite images

[...]

I'm pretty sure that almost all the "high resolution" data is aerial
photography (from an airplane not from a satellite). It's thus
available only in areas where someone had a reason to collect this
imagery, had it digitized, and was willing to license it to Keyhole/
Google under reasonable terms.

I suspect the licensing of some of the datasets they're using restricts
how much access Google can give people (like the restrictions on printing
resolution in the free version, etc.).

G.

Gavin Scott said:

I'm pretty sure that almost all the "high resolution" data is aerial
photography (from an airplane not from a satellite).

Hi Gavin,

I've learned, that many hi res data are from satellite. You can verify
this at fast moving objects, like planes in the air. The have "ghost
twins" like here:
<http://maps.google.com/maps?ll=53.628595,9.984201&spn=0.003582,0.007499
&t=k&hl=en>

hth
Anton

Anton Betzler said:

Hi Gavin,

I've learned, that many hi res data are from satellite. You can verify
this at fast moving objects, like planes in the air. The have "ghost
twins" like here:
<http://maps.google.com/maps?ll=53.628595,9.984201&spn=0.003582,0.007499
&t=k&hl=en>

hth
Anton

Anton,

I see the effect, but how does that prove it's a satellite image?

Andy

On Wed, 24 Aug 2005 17:58:35 -0000, [email hidden] (Gavin Scott)

Quoted message said:

In sci.geo.satellite-nav Nick Hopton said:

Just to mention that even though the high-resolution satellite images

[...]

I'm pretty sure that almost all the "high resolution" data is aerial
photography (from an airplane not from a satellite). It's thus
available only in areas where someone had a reason to collect this
imagery, had it digitized, and was willing to license it to Keyhole/
Google under reasonable terms.

I suspect the licensing of some of the datasets they're using restricts
how much access Google can give people (like the restrictions on printing
resolution in the free version, etc.).

Higher resolution images of many areas are publicly available, but
they are not accessible via Google Earth.

For example, www.multimap.com has detailed aerial images of large
sections of the UK, but GE only has low-resolution images of those
same areas. Google must have been usable to license those maps for
their own use.

Chris

Andy Champ said:

Anton,

I see the effect, but how does that prove it's a satellite image?

Andy

Well, not only that effect, but...

- There are some images of airplanes far from airports. An airplane
taking those pics is much higher than the photographed one... so it is
much higher.

- Is so high, in fact, that there are some images with clouds, but yes,
airplanes usually fly over clouds.

- It is very uncommon for an airplane to fly OVER an airport if it
doesn't plan to land.

- The images are usually isolated. If you have an airplane to do a
track, I suppose that the usual would be photograph every part of your
track, and not just isolated regions. This looks like Google has bought
satellite time, and centered the efforts in important places.

- It is interesting that most images long strips of pics (you can see
that with the DG view) in North-South orientation.

My idea is that the images has been taken from a satellite.

Maybe some parts of the world are taken by plane and others by
satellite... that could explain why some areas has better quality than
others. Not just the high-res and low-res areas, but not all the
high-res areas are equally good. Tokyo images are really good!

Regards.

No more doubts:

Google Earth images are copyrighted by DigitalGlobe.

Go to their web, http://www.digitalglobe.com/ and you can see how it
works. It is a satellite, with a maximum precision of 60cm in images if
satellite is at nadir (just over the photographed point) and 2.44m if
near the horizon.

Regards.

You can't expect even a company of Google's size to know everything, I
have some hi-res pictures of the ground around my house on my site but
it is not accessible via GE either.
The good thing is that you can add it yourself if you so want it, and
if you post it on the keyhole BBS it does become publicly available.

Nacho said:

Andy Champ said:

Anton,

I see the effect, but how does that prove it's a satellite image?

Andy

Well, not only that effect, but...

- There are some images of airplanes far from airports. An airplane
taking those pics is much higher than the photographed one... so it is
much higher.

- Is so high, in fact, that there are some images with clouds, but yes,
airplanes usually fly over clouds.

- It is very uncommon for an airplane to fly OVER an airport if it
doesn't plan to land.

No it's not. Sorry... Lots of aircraft traversing will fly directly over
an airport at altitude. It's a good waypoint. Stand at Heathrow sometime
& watch the contrails going direct overhead...

Nacho wrote:

<snip>

Quoted message said:

- It is very uncommon for an airplane to fly OVER an airport if it
doesn't plan to land.

<snip more>

In this case the shadows of the aircraft (both images!) being sharp and
nearby show that the aircraft is at very low altitude. However I still
don't see how you can tell from the double image that the photo was
taken from a satellite, and not an aircraft at a high-ish altitude.

Andy

On Thu, 25 Aug 2005 23:05:25 +0000, Andy Champ <[email hidden]>

Quoted message said:

Nacho wrote:

<snip>

Quoted message said:

- It is very uncommon for an airplane to fly OVER an airport if it
doesn't plan to land.

<snip more>

In this case the shadows of the aircraft (both images!) being sharp and
nearby show that the aircraft is at very low altitude.

This is an old trivia question. The shadow on the ground cast by an
aircraft is the same size regardless of what height the aircraft is
flying at.

Chris

On Thu, 25 Aug 2005 22:02:08 +0100, Hamie <[email hidden]>

Quoted message said:

Nacho said:

Andy Champ said:

Anton,

I see the effect, but how does that prove it's a satellite image?

Andy

Well, not only that effect, but...

- There are some images of airplanes far from airports. An airplane
taking those pics is much higher than the photographed one... so it is
much higher.

- Is so high, in fact, that there are some images with clouds, but yes,
airplanes usually fly over clouds.

- It is very uncommon for an airplane to fly OVER an airport if it
doesn't plan to land.

No it's not. Sorry... Lots of aircraft traversing will fly directly over
an airport at altitude. It's a good waypoint. Stand at Heathrow sometime
& watch the contrails going direct overhead...

That's the way I was taught to fly when I did my pilots license.
Whenever possible you plan a route to your destination that overflies
airports on the way. As well as providing convenient visual waypoints,
if you have a technical problem enroute and need a place to land you
will already know how to find the nearest airport.

Chris

Chris Blunt said:

On Thu, 25 Aug 2005 22:02:08 +0100, Hamie <[email hidden]>
wrote:

sn't plan to land.

Quoted message said:

Quoted message said:

No it's not. Sorry... Lots of aircraft traversing will fly directly over
an airport at altitude. It's a good waypoint. Stand at Heathrow sometime
& watch the contrails going direct overhead...

That's the way I was taught to fly when I did my pilots license.
Whenever possible you plan a route to your destination that overflies
airports on the way. As well as providing convenient visual waypoints,
if you have a technical problem enroute and need a place to land you
will already know how to find the nearest airport.

Chris

Yes, sorry, I was wrong. I did a quick search and I found that... I'll
recheck my arguments next time!

Regards.