Geoportal better than Google Maps!

[Forhorse]

Ben from the links I gave above, and if I understand correctly, the first generation of satellite had a resolution of 10m.
I understand that 1 pixel = 10m, which is huge! not enough to see houses or even cars as with the current generation and is available on geoportal.
Or I'm wrong.

[Christophe]

Uh yes I think that has gusto ....

You can have 1 pixel = 10 m with a 10 Mpixel, 100 or 1 GPixel sensor ...

What matters is the quality of the optics, its settings and especially the shooting distances, the sensor itself has almost nothing to do with it ... it cannot do anything "against" the optical laws. physics. The goal is there for that ... and goals it's been a long time we mastered them ...

The best sensor in the world without a good lens will not do any good. Just as the opposite.

Example: by taking a picture of the moon without a telescope and with a modern consumer camera at 10Mpixel, I think you are more than 1 pixel = 10m ... probably closer to 10 km ... after that depends on camera zoom.

Another example: Spot is at an altitude of 822 km, according to Wiki.
Take a picture with an 100 Mpixel at 822 km ... to see.

If I was not lazy I would calculate the distance triangle ... but I'm lazy ...

Correct: 2 2005 Mpixel digital camera can do better photos than an 12 2010 Mpixel camera ...

[oiseautempete]

Géoportail uses a mixture of aerial photos taken by IGN aircraft (Falcon 20) and satellite photos ...

the Hurel Dubois, an IGN aircraft designed in the 50 years, with a large aspect ratio, intended for high altitude flight and which has long been used by the IGN (up to 1985) ... Boeing is working on a Hybrid airplane (electric motors + thermal generator) with long elongation that looks like his son ...


Boeing

[Christophe]

Super Bird! Thank you for the info.

The wiki page: http://fr.wikipedia.org/wiki/Hurel-Dubois_HD-34

On the other hand it was not going in "so high altitude" (well it depends on your definition, me I thought "high" = above the 10 000m): 3000 to 7000m.

So the IGN only uses small planes since 1985?

[chatelot16]

I told myself that these aerial view was too fine to be taken by satellite, but rather by plane

at the time of the dubois hurel, he carried 2600kg of photographic material, it was useful to have a specially adapted airplane

I imagine that today the material is so much lighter that a smaller plane is enough

[oiseautempete]

Super Bird! Thank you for the info.

The wiki page: http://fr.wikipedia.org/wiki/Hurel-Dubois_HD-34

On the other hand it was not going in "so high altitude" (well it depends on your definition, me I thought "high" = above the 10 000m): 3000 to 7000m.

So the IGN only uses small planes since 1985?

Yes finally "high altitude" with a piston engine plane ... the Hurel Dubois was very popular because of its excellent stability in flight (important for the photos) and its long range in flight ...
The IGN also uses twin-engine Beechs in addition to Falcon 20s.
The quality of the photos is comparable thanks to the improvement of the cameras

[Christophe]

I told myself that these aerial view was too fine to be taken by satellite, but rather by plane

Well, honestly I don't know: google maps / earth is satellite right? Some areas are "bugged" and in some places it is more precise than geoportail. The sat "general public" are at 10 cm resolution not?

Also the bottom of the oceans appears for some time on google earth.

So we have to believe that some satellites are now able to estimate the depth of the oceans? If yes I would like to know the name of the method (it will recall the affair of the planes sniffers (oil) of Giscard hihihi)

Because it would surprise me if we had mapped the entire seabed "on the boat" ... already that we have trouble with coastal areas!

[elephant]

Forhouse said:

Yes for the transmission, but for the photo sensor?

Well, it's still decades that we made tube images.
(vidicon, orticon, plumbicon, saticon, salpticon, kelvicon, etc. )
Some cartographic satellites also work with a very high definition "1 line" sensor, and it is the movement of the satellite which makes the vertical scan.

[oiseautempete]

Some areas are "bugged" and in some places it is more precise than geoportail. The sat "general public" are at 10 cm resolution not?

The resolution of the commercial satellites is of the order of the meter (one sees the cars, but without identifying them), in some cases the resolution rises to 50cm, but to 10cm one enters already in the military field ...
Some areas are voluntarily limited resolution like the military zones ... at the beginning on Géoportail there were even whites, ridiculous considering that we had images on Google Earth ...

[elephant]

Christopher said:

Because it would surprise me if we had mapped the entire seabed "on the boat" ... already that we have trouble with coastal areas!

I think the opposite: we have sonar since the 50 years, both on fishing boats and on transport and military boats. It is obvious that the mapping of the Sargassum seabed is less precise than that of Concarneau bay (I have sailed there, these maps are incredible)

And there are many submarine fighter jets.

The military was very interested, especially to open the way to submarines.