|English to French translations [PRO]|
|English term or phrase: reflections off the ground surface|
|Other problems introduced in the aerial imagery include hotspots, shading and other atmospheric aberrations. Some of these problems are caused by the angle of the sun and reflections off the ground surface or features.|
Please translate 2nd sentence. First sentence would be helpful too.
Source: EOM Airborne: Digital Orthophoto Imagery: Elements of a Seamless Image Database
By Mark Klimiuk
A "hotspot", in photographic jargon, is an area with too much light. To be distinguished from an area with with specular (by points) reflections (like a reflection from shiny metal or water in motion). If I'm taking a portrait in a studio with lights, and you've got a zone on your forehead that's too bright with a loss in detal, then I've got a hotspot on your forehead. The reflection from your eye is not a hotspot because its specular.
The hotspotting problem usually only occurs on wide-angle aerial photography when the sun is more or less behind the camera (when you can draw a nearly straight line between the sun, the camera, and the hotspot).
One of the problems in aerial photography that distinguishes it from regular photography (on the ground) is that the light source is usually behind the camera. What occasionally happens is a little complicated to explain to someone not familiar with photographic materials, so I'll have to explain everything.
Think of a shadow as an area that the sun cannot see. When you're taking a photo from the air, there are also areas that your camera cannot see. The zones your camera cannot see coinciding with the ones the sun cannot see means that the area around the zones appears to be brighter than it is because you cannot see the shadows.
What compounds the effect and turns it into a problem is that halation occurs because of the sun's intensity.
When you take a picture, light goes through the lens and strikes the film. Not all the light is stopped at the film, some of it continues through to the film plate (the pressure plate that holds the film flat). A portion of that light is then reflected back to the film around the area the light went through initially, creating a very fine halo effect (halation) which fills in the shadow areas around the reflections filling them in (and creating a loss in detail).
Photography is not additive, things are multiplied. A zone is twice as bright as another, not 13 units brighter.
When you've got an area reflecting, lets say, 50 units of light next to an area reflecting 5, and the halation problem feeds 10 units of light back to the whole area, what you get is the 50-unit area now appearing to reflect 60 units (20% more) and the 5-unit area appearing to reflect 15 units (three times as bright as it is).
This all occurs in a very small area of the film (millimeters big) and when the area affected (the 5-unit area) is next to a 8-unit area, the two areas now appear to reflect the same amount of light. A 8-unit area can easily be distinguished from a 5-unit area because it reflects 60% more light. Add 10 units to each and you get a 15-unit area next to an 18-unit area, which is a difference of only 15% (measurable only by highly sensitive instruments like $5,000 photolab densitometers). To most people (and the film), the two areas appear to have the same "darkness". The area appears to be brighter than it actually is.
Because this does not occur over the entire picture, it shows up as an area (called a hotspot).
One of the problems I see in your text is that the author is not 100% technically solid (hotspotting is not an atmospheric aberrations, as the text implies) and you're going to have to fill in the blanks and re-interpret the text.
Now my attempt at translating. Adapt this, obviously, to your text as you'e written it.
D'autres problèmes particuliers à la photographie aérienne sont la production de taches lumineuses ou sombres ou des abérrations causées par l'atmosphère. Certains sont des produits de l'angle du soleil et des réflections de la surface ou des particularités du sol.
Personally, I'd change "sol" to "sujet" because some of the problems occur on water, but I'll leave that decision to you.
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"réflections projetées par la surface du sol"
A suggestion based upon context given.
Hope you find it useful! :)
Note added at 2002-07-14 12:30:42 (GMT)
Your full translation:
>>> L\'imagerie aérienne compte d\'autres problèmes tels que les zones de chaleur et d\'ombre ainsi que d\'autres aberrations/instabilités atmosphériques. Certains de ces problèmes sont dus à l\'angle des rayons solaires et à leurs réflections sur le sol ou aux caractéristiques de celui-ci.<<<
See also the following:
... études récentes, deux processus d\'inte- raction sociale influencent l\'estime de
soi et l\'image corporelle, à savoir « l\'appréciation par réflection » et ...
... 2) Les télescopes à réflection contiennent des miroirs concaves (courbés vers
l\'intérieur ... qui renvoie à son tour la lumière à un endroit où l\'image ...
... Figure 6: Réflection de Phong avec divers coefficients. Lumière ambiante. En synthèse
d\'image chaque source de lumière génère un certain temps de calcul ...
Note added at 2002-07-14 18:27:30 (GMT)
P.S. Use \"zones sensibles\" FOR \"hotspots\" as indicated in the following links:
PHOTOGRAPHIE AERIENNE, La société ALTICOLOR est spécialisée dans la prise de
vue ... évidence d\'un environnement; l\'identification et la délimitation de zones ...
... La simple comparaison de quelques clichés de photographie aérienne montre ... superficie
souvent importante, mériteraient d\'être considérées comme des zones ...
... variable) : les détails deviennent donc encore plus fins dans les zones \" sensibles ... épais
brillant, pour un rendu équivalent à celui d\'une photographie ...
... 4 - Une photographie aérienne IGN de l?ensemble de la zone ... classées selon leur
caractère dominant : garrigue, région boisée, région agricole, zones ...
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Parmi les autres problèmes posés par l'imagerie aérienne,
figurent les zones de chaleur et d'ombre ainsi que d'autres aberrations atmosphériques. Certains de ces problèmes sont liés à l'angle des rayons solaires et à leur réflexion par le sol et les divers accidents de terrain.
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