Photogrammetry
Photogrammetry, the method of getting useful information from photographs.
Photogrammetry is the technique of estimating the geometric properties of objects from photographs.
An image is a two dimensional representation of the object. Though photographs allow us to visualize the actual scenes and objects which are depicted in it, there is an important component that adopts making that visualization near to reality. That input is our brain which either has knowledge of the scene or makes assumptions about this. This visualization is good enough for most everyday purposes, but is insufficient for some applications. As an example we cannot tell just by looking at a photograph whether the car that is depicted in it is an actual car or perhaps a small model unless there's some other real life object beside it to compare it with.
Photographs also are afflicted by the lack of the third dimension. All real world objects have three dimensions. A photograph does not show the third dimension, that is the depth. The reason we are able to interpret the depth of the scene is mainly due to effects of light and shadows and also the relation of objects to other objects that we know about rather than just from information captured within the photograph.
Techniques of photogrammetry:
Photogrammetry uses methods from many fields including geometry and optics. It has four main aspects which are inputs and outputs. The main reason these aspects are generally inputs and outputs happens because if we know two or more of these aspects you'll be able to find the other unknown aspects. Let us take a look at these four aspects:
a) The 3D co-ordinates of objects in a photograph: This is the depth of the objects in the photograph as well as their relative position to each other in the third dimension.
b) The image co-ordinates on the photograph: These are the actual co-ordinates from the objects on the 2D photograph.
c) The exterior orientation or perspective: This is the point of view or angle of the camera.
d) The geometric parameters of the imaging process: This is called the inner orientation. This really is basically the parameters from the camera such as the focus, the depth of field, the errors and the distortions.
There is one additional ingredient that photogrammetry uses and that is the extra information that we know concerning the photograph such as the actual size of objects or the scale from the photograph.
Applications of photogrammetry:
Photogrammetry has many applications. The most common application is to locate the third dimension of the scene by photographing the scene from two different camera locations. The difference between the co-ordinates of the objects from the two different points of view enables algorithms to calculate the 3rd dimension.
This method has wide ranging applications ranging from areas like preparing topographical maps, architecture, engineering, manufacturing, quality control, geology, archeology, meteorology, police investigations and computer graphics for starters. Archeologists use it to produce plans of huge complex sites. In the absence of other objective data it is used by meteorologists to gauge the wind speeds of a storm. Accident investigators who sometimes need to conduct investigations quite a long time after the event by using photographs use it to reconstruct the accident from positions and damages to vehicles.
The principles involved with Photogrammetry are not just the invention of man. This is precisely the technique our brain uses to gauge the third dimension of the objects that people see. We have two eyes each of which gives a slightly different view of the scene. This subtle difference is then interpreted by our brain allowing us to perceive the 3rd dimension.
Photogrammetry is the technique of estimating the geometric properties of objects from photographs.
An image is a two dimensional representation of the object. Though photographs allow us to visualize the actual scenes and objects which are depicted in it, there is an important component that adopts making that visualization near to reality. That input is our brain which either has knowledge of the scene or makes assumptions about this. This visualization is good enough for most everyday purposes, but is insufficient for some applications. As an example we cannot tell just by looking at a photograph whether the car that is depicted in it is an actual car or perhaps a small model unless there's some other real life object beside it to compare it with.
Photographs also are afflicted by the lack of the third dimension. All real world objects have three dimensions. A photograph does not show the third dimension, that is the depth. The reason we are able to interpret the depth of the scene is mainly due to effects of light and shadows and also the relation of objects to other objects that we know about rather than just from information captured within the photograph.
Techniques of photogrammetry:
Photogrammetry uses methods from many fields including geometry and optics. It has four main aspects which are inputs and outputs. The main reason these aspects are generally inputs and outputs happens because if we know two or more of these aspects you'll be able to find the other unknown aspects. Let us take a look at these four aspects:
a) The 3D co-ordinates of objects in a photograph: This is the depth of the objects in the photograph as well as their relative position to each other in the third dimension.
b) The image co-ordinates on the photograph: These are the actual co-ordinates from the objects on the 2D photograph.
c) The exterior orientation or perspective: This is the point of view or angle of the camera.
d) The geometric parameters of the imaging process: This is called the inner orientation. This really is basically the parameters from the camera such as the focus, the depth of field, the errors and the distortions.
There is one additional ingredient that photogrammetry uses and that is the extra information that we know concerning the photograph such as the actual size of objects or the scale from the photograph.
Applications of photogrammetry:
Photogrammetry has many applications. The most common application is to locate the third dimension of the scene by photographing the scene from two different camera locations. The difference between the co-ordinates of the objects from the two different points of view enables algorithms to calculate the 3rd dimension.
This method has wide ranging applications ranging from areas like preparing topographical maps, architecture, engineering, manufacturing, quality control, geology, archeology, meteorology, police investigations and computer graphics for starters. Archeologists use it to produce plans of huge complex sites. In the absence of other objective data it is used by meteorologists to gauge the wind speeds of a storm. Accident investigators who sometimes need to conduct investigations quite a long time after the event by using photographs use it to reconstruct the accident from positions and damages to vehicles.
The principles involved with Photogrammetry are not just the invention of man. This is precisely the technique our brain uses to gauge the third dimension of the objects that people see. We have two eyes each of which gives a slightly different view of the scene. This subtle difference is then interpreted by our brain allowing us to perceive the 3rd dimension.
