Geo Week News

August 6, 2014

Laser Scanning for Forensics: An Easier Way to Create Plan Drawings


Forensic laser scanning is now well rooted in Europe and North America and has passed the “initiation” stage. Many agencies are realizing how powerful laser scanners can be for documenting large and small scenes in great detail. Consequently, we can expect a great adoption of 3D technologies with significant growth over the coming years.

Software Challenges 
What is surprising is that software developers still haven’t found an efficient solution for delivering the data in the same format in which it was captured. That is, there is still no good way to deliver data in the form of a point cloud. As a result, the most common practice for forensic agencies when creating deliverables is to document scenes in 3D, then to create 2D plans drawing by manually tracing over the point cloud. 

There are several programs that you can use to do this. Some of these are marketed directly to forensic agencies, while others are used in many industries:

  • CrimeZone/CrashZone
  • MapScenes
  • EdgeFX
  • AutoCAD
  • PointCab
  • Veesus

PointCab is not very well known in forensics, but is well suited to 2D drawings. It excels at creating 2D section drawings from point clouds. Veesus (Arena4D) just introduced some new polyline features to their software that allow for the creation of line drawings based on the point cloud. They also have a very interesting way of presenting scan data captured from many sources in combination with photos, videos, documents, and other data. So, things are moving in the right direction.

Figure 1. A typical plan drawing made by tracing over point cloud data to create lines and points.

Figure 2. Sample plan drawing using only title block and notation information on top of a point cloud. There is no need for line tracing and the point cloud of the scene provides greater detail.

 Still, many agencies I work with ask if there is a better, more efficient way to provide plan drawings, one that does not require you to trace features manually. My answer is yes, but it to do so, you’ll have to present the data in the form in which it was captured – as a point cloud. 

Simply take an orthographic view of the point cloud and package it as a plan drawing. Using the point cloud itself saves you from the tedious and time-consuming process of point tracing. It also allows you to retain the benefits provided by 3D scanners, since a scene properly documented in 3D is much closer to reality and is a much better interpretation of a crime scene than a 2D drawing.

The biggest challenge at the moment for doing this is software. Not many software packages allow you to combine a 3D orthographic view of a point cloud with a title block, scale, and other notations. We need software developers to provide a more efficient way of working with point cloud data to minimize the amount of work required to create a useable deliverable as well as to maximize the visualization effect for greater understanding. Hopefully, as we move forward and begin to use the point cloud more and more, we will see greater functionality in many existing and upcoming software packages and in turn, a more efficient method of creating and presenting plan drawings for forensic purposes.

Other Issues 
Software may be the biggest practical issue, but there are other things to know for those who want to use 3D deliverables for forensic purposes. 

  • In some cases, a line drawing makes more sense. For example, a very quick scan of an intersection from only two or three positions may not provide enough detail in the point cloud to view it from the top down.
  • In the case of very graphic scenes, it is possible that part of the data will need to be hidden or removed so that juries are not unnecessarily prejudiced. One way to accomplish this is to scan the crime scene area once with all evidence in place, and then scan it a second time with graphic evidence removed. The graphic evidence can be used by investigators to do some type of analysis, while the “cleaner” version could be used as a demonstrative piece of evidence at trial.
  • In the forensic or legal industry, there is a long history and culture associated with procedures, precedence, and a tendency to avoid anything “new,” especially when it is unfamiliar, poses a risk, or could complicate a case. Because judges, attorneys, and juries are accustomed to traditional line drawings, it’s possible that at first there could be some resistance.
  • On the other hand, juries are becoming more and more in tune with 3D technologies, video games, and realistic 3D films and effects. There is also the “CSI” effect, where judges and juries come to expect a higher level of technology used for delivery in court. In my own experience delivering virtual 3D reconstructions in court, I have seen that juries understand and appreciate laser scanning technology and virtual representations of crime scenes.

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