I explain with pictures ...

First it's the preview, a ball on a casting shadow flor and a background picture ...

The question is, what is the fonctions to have the reflexion picture in front of the ball ?

You can shirt the position of the image in the image node using the U Offset and V Offset entries.  Keep the values small, between 0 and 1.

I'ts fake reflection anyway, don't expect to get something as realistic as a real raytraced reflection with a skydome and a 3D road and terrain object...

Dont worry for the reflexion ;-)

This will not work. When you look at a sphere, it reflects about 90% of the 360 degree universe around it.

Your photo is only about 10% of the universe, maybe less.

For the perspective to work out correctly, imagine a photo suspended behind the camera of what the ball can see, like a billboard. You put your photo of the road in that direction on the billboard.

Now imagine rendering the sphere. You will see a reflection of a billboard with your photo on it, along with all the rest of the sky and ground. You will not see the billboard fill the sphere.

The only way this can work is if you have a full 360 by 180 degree equirectangular image, as you would use on my Environment Sphere. That is what should be in your sphere_map.

Yes BB i can use youre sphere but i dont have the picture for ... I do with the "moyens du bord"

I try ...

Completely agree, BB. It may be good enough for a very quick and dirty solution, but for the sphere_map node to work, you indeed need a panoramic image.

The funny thing is, this empty desert scene is easy to create in Vue or Bryce, including the road. Vue Infinite can render it out as a panoramic image - and it'll neatly generate a HDR IBL map for you too. Trouble is, you need a high resolution (like 4800x2400) to make it work decently (the IBL map can be smaller, by the way)

What I do with background images is note the angle and color of the primary source of light in the pic, then line up the light sources in Poser to line up. Beyond that...see the above.