Friday, November 13, 2009

Microsoft's Photosynth: A Future Forensic Tool?

From Forensic Magazine:

The digital camera is by far one of the most common tools for documenting accident and crime scenes all over the world. The low cost, ease of use, and its value as an important communication tool makes it a standard instrument for anyone in Forensic Identification. Even though film cameras are now almost completely obsolete and digital formats are the modern successor, many of the methods and techniques for capturing photographs have remained relatively unchanged. However, with the advent of new software and technologies that have branched out of photogrammetry (i.e. science of getting measurements from photographs), digital cameras are finding new uses as accurate measuring instruments too.

If you haven't heard about Microsoft's Photosynth, you might want to check out this neat little application that is provided freely by Microsoft. Photosynth is a new way of organizing your photos of a particular object or environment such that the photos are spatially oriented with respect to one another. Unlike panoramic images, where you can stitch a number of photographs together to create a 360° image of a scene, Photosynth is a combination of technologies that solve for the common features between photos and how each of the photos are oriented with respect to one another in 3D space. As the images are matched, the camera positions can be calculated and the matching points in each of the images are created as a 3D point.

These "points" define accurate features in 3D space that are common between photos and by taking enough photographs of an object, it is possible to construct a point cloud from the "synthed" images. In effect, this makes it one of the only free 3D scanners that can be utilized to get relative distances between point features of an object.

Although Photosynth was originally intended as a new and creative means of presenting photographs, what makes it technically appealing is that it can solve for the relative spatial relationships between photographs without knowing anything about the camera that took the photograph, and it does it relatively quickly.

The impact of this type of technology is that first responders, forensic technicians, and investigators can quickly gather a large number of overlapping photographs without the need for special targets, expensive equipment, or complicated software. The user just needs to take a lot of photos that cover the object all around and close up (either by physically moving closer to the object or by using a zoom lens). Once the photos are captured, they can be easily processed in Photosynth by a user with little to no training. There are actually very few steps involved in creating a "synth".

However, this simplistic approach is one of the areas where further development is needed since there is little control over the resulting point cloud and there are no integrated measuring tools. The solved points are somewhat a by-product of the technology and currently, exporting the point cloud requires a rather complicated process, (not for the faint of heart). Any post analysis of the point cloud requires the use of third party software for viewing and cleaning of stray points and "noise". (Another possible area of development).

Read the rest of the story by
clicking here.

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