Photogrammetry

Photo courtesy NASA Some crime scene photographers use laser-scaling devices like this one, which projects a pattern of dots that acts as a point of reference.

Another way to recreate a crime scene using computers is to use photogrammetry. Photogrammetry is a technique where a computer combines many different photos of a location into a 360-degree image. Viewers can look around by using various controls, the most common of which is using your mouse to click and drag on the photo itself to change the view.

Some photogrammetry systems use a special camera mounted on a tripod that can rotate the camera's view in 360 degrees. The camera takes a series of pictures and sends them to a computer that has proprietary software designed to combine the photos together to make a seamless photograph of the environment. Users can change the point of view for the photo, turning in any direction.

These photogrammerty systems are much more efficient than a human photographer snapping photos from every viable angle. However, since it's on a stationary tripod, the camera won't capture any areas in an environment where the view is obscured from the tripod's position. Investigators have to move the tripod and take another series of photos to capture that perspective.

In many ways, photogrammetry has significant advantages over creating a graphical representation of a crime scene. For one thing, you don't need to be a skilled programmer or graphics designer to use the hardware and software. The machinery and computer programs do all the work for you, creating comprehensive photos in a few minutes. Another advantage is that it's not just a representation of the crime scene -- it's a series of actual photographs. Viewers won't be distracted by an unrealistic object model or a poorly chosen texture.

But there are some distinct disadvantages. Unlike a virtual model of a crime scene, you can't view a room from any angle -- you can only look around from where the investigators set the tripod for the pictures. Unless the investigators put the tripod in multiple places within the same space, you're stuck viewing a room from one fixed point. Photographs also aren't very good at accurately showing the depth of a view -- objects may seem to be closer or farther away than they should be.

Where in the World? So far, European police forces have explored virtual-environment technology the most. Forces in England and Italy pioneered the use of VR technology in forensics investigations. Some police stations in Australia also use virtual environments in crime scene investigations. While it's been slow to catch on in the United States, more and more police officials are looking into using this technology to support their investigative efforts

Some photogrammetry software packages are very affordable, but the hardware tends to be expensive. For some police departments, the expense is justified because the software doesn't require someone with special training to use it. Some programs even allow users to use a normal digital camera instead of a specialized photogrammetry device. These programs require the photographer to shoot the same scene from multiple angles, then use the computer software to identify identical points in each photo. The software can then create a three-dimensional model by triangulating the identical points in each photo. This solution is much more affordable, but is less comprehensive than advanced photogrammetry techniques and requires more man hours to use.

In the next section, we'll look at some applications for VR crime scene technology.

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