What is going on with this seemingly low-flying plane seen in Google maps near the British Museum? It’s still visible regardless of how closely I zoom in. Link: Low-flying plane
Why would you expect it to become invisible when you zoom? You are just looking closer at the same photo.
What makes you say it’s a low-flying plane? How do you know it’s not flying at a completely normal aeroplane height?
Fair enough; I’ll rephrase. It looks to be low-flying regardless of the zoom level. Sometimes there is a switch from satellite photo to airplane-base photo as you zoom in.
Note that if you can find the plane’s shadow it would be easy to determine its height. Unfortunately, that is not be easy to do in an urban landscape.
I’ve seen this illusion in real life. When flying at cruising altitude, I’ve seen a plane that appears to be just above the ground. Then I realize that, from the ground, my own plane would look like a small black dot. That’s when I realize that, in spite of appearances, that plane is actually much closer to me than it is to the ground.
Satellite photos exhibit almost no perspective distortion (i.e. differing sizes of near and far objects) because of the high level of zoom (large focal length), and the fact that the altitude of any object over the ground is minimal compared to the altitude of the satellite itself. Essentially, images taken with a large focal length are essentially “flat” - all objects appear the same size regardless of their relative distance from the camera.
That airplane could be flying at just about any altitude. It is most likely preparing to land at Heathrow, perhaps 5,000 feet AGL or so.
Here is a neat demonstration from Wikipedia of the effect of changing focal length:
A satellite photo is like the photo on the bottom, only moreso.
I don’t think it’s going to be as low as it looks - if you scroll due west about half a mile, you’ll find the BT Tower - one of the tallest buildings in London - I don’t think a plane would be allowed to fly low as close to that tower as this.
The shadow of the BT Tower provides a good indication of the direction we should look in for the plane’s shadow, but I can’t find it amongst all those buildings.
My understanding is that Google Earth photos are not satellite photos, they’re high altitude aircraft photos. Satellite photos (even spy satellites) don’t have high enough resolution to show the level of detail you get with Google Earth/Maps.
Yes, I know that Hollywood would have you believe that there are spy satellites good enough to “read the headlines of a newspaper on the ground” but that’s a myth and not actually achievable in the real world, or so I’m imformed by people who seem to know what they’re talking about.
Google Earth photos are a mix of satellite and survey aircraft photos. The low resolution photos used for when zoomed out and some areas that don’t have high resolution photos are taken from a satellite. The high resolution ones where you can see aircraft and cars etc are taken from survey aircraft.
The aircraft in the link is about 12 nautical miles from Heathrow and positioned such that it would shortly be turning final for one of the westerly runways. At that distance it would most likely be somewhere around 3600 feet above the ground.
How would you do this? Wouldn’t you need to know the angle of the sun at the time the photo was taken?
You are already looking at an aeroplane based photo, the switch from satellite to aeroplane has already happened, when you zoom in you are just zooming in on the same aeroplane based photo.
Sometimes there’s another photo from a closer airplane when you zoom in.
Yes, indeed. And you can see from the OTHER shadows that the sun is ALMOST directly overhead. But it’s not EXACTLY overhead, and the shadows are pretty short, but they do appear to the west and slightly north.
Now, take a look at the shadow where the plane’s nose is. It is pretty obvious that this somewhat-circular shadow is from the tree just off the southeast tip of the plane’s nose. Going to Google Street View in that same area, you can see that the trees and buildings are fairly tall, about 7 stories or so, not skyscrapers by any definition. Thus, the shadows are some fraction (1/4?) of the height of their objects.
From all the above, it is obvious that if the plane was as low as it appears to be, its shadow would be right below it. I cannot find the shadow, but it is not anywhere in the immediate block or two away. This would seem to prove that the plane is very very high up.
Regardless of whether the photo of the plane was taken by a satellite or a plane, the photo of the plane’s shadow is probably in a different shot and we’ll never find it.
The aforementioned BT Tower (more or less due west of the plane) would probably make quite a good reference for calculating the angle of the sun (hint: the sun is never going to be directly overhead in London - it’s a maximum of a little over 60 degrees)
That’s not universally true and is increasingly not so. The big advantage of aerial imagery is that in many areas it’s done by government agencies and so it’s free. When possible, Google will replace the aerial imagery with huge high-res satellite images which have the same resolution as the aerial ones but don’t have the artifacts from stitching the strip photos together. Judging on how far out you can zoom from this place in London without any obvious stitching, I’m betting that’s what we’re looking at here.
Basic physics would point to a serious limit to what spy satellites can resolve; a 2.4 meter mirror like used on the KH-11 satellites can resolve about 6" on the ground, assuming no atmospheric distortion, etc…
So they could see a newspaper, but couldn’t see anything on it.
Commercial satellite imagery is somewhere in the half-meter range, both due to legal reasons and practical ones.
So the upshot is if you can discern anything smaller than about 18 inches in size, you’re more than likely looking at an aerial photo of some kind.
The imagery over London looks like a satellite image to me. Satellite images are usually taken from a nearly vertical angle, because this is easiest to process and the most generally useful.
It is not feasible to take such photographs from an airplane and simultaneously cover a large area, so aerial photographs usually show an obvious oblique (non-vertical) angle from the camera to the objects on the ground.
For instance, this area of Denver was photographed by an airplane. Note the obvious non-vertical camera angle, perhaps 20-30 degrees - you can’t see the other side of the buildings. If you zoom out, Google will switch to satellite imagery, which was taken from a nearly vertical angle.
They use a special camera that shoots straight down and makes a continuous image as the plane flies in a straight line. The only issue with oblique angles is with the objects to either side of the flight path, but this is generally not noticeable with this sort of imagery. At what is usually the highest Google Maps/Earth resolution, aerial and high res satellite imagery are essentially indistinguishable.
The image you linked to is part of Google’s 45 degree view imagery, which is higher resolution than the “normal” high res imagery and is only available in certain cities. The tilted angle is only to better show buildings and such, not because of any technical limitation-- they could have shot just as high resolution imagery straight down.
ETA: also to see something cool, when you’re looking at a 45 degree image, grab the ring around the arrows in the upper left. There’s actually up to 4 different images from 4 different fly-by’s, which is sometimes obvious from things like parked cars moving around.
In addition to what GreasyJack said, aerial photographs are usually orthorectified before being used in mapping applications. Otherwise the road map overlay would be wildly off.
It doesn’t look very low to me, it’s as large as some of the city blocks in the image and it’s several times larger than the transfer truck and trailer off its left wing, indicating that it’s closer to the camera than those objects.