General Terminology

The use of computer graphics to accurately represent an object, process, data, or evidence. A reconstruction is based on physical evidence and is used as substantive evidence. The reconstruction process involves documenting and analyzing the physical evidence, then providing a report or visualization of findings.

A creative work used to demonstrate evidence or help explain something (e.g., an animation to visualize a witness account).

A mobile device that is typically smaller and lighter than other types of 3D scanners and can be moved around a piece of evidence or a scene. Most hand scanners have the ability to track their position with reference to an object or piece of evidence being scanned and they capture 3D details in snapshots or “frames”. These frames are subsequently stitched together to make one larger 3D scan.

LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. Lasers are a light source where the light consists of a narrow wavelength (i.e., distinct color) and is focused into a fine beam.

A 3D measuring technology that uses lasers as the light source. By detecting the reflection of the laser, visible or invisible to the eye, it is able to accurately measure the distance from the scanner to an object or surface. This information can be then used to create a map of the scene for documentation and analysis.

LiDAR is a technique used for remote sensing that stands for Light Detection and Ranging. In a measurement using LiDAR, emitted light reflects off the surface being measured and returns to a sensor. The distance to a point is calculated by comparing the emitted signal to the returned signal.

A technique that creates measurements of objects from photographs with the use of cameras. Terrestrial photogrammetry is taken from the ground while aerial photogrammetry may be taken from a drone. Photogrammetry can reconstruct dense meshed models of evidence or large outdoor spaces.

A dense set of points that accurately represent a surface, object, or environment. These dense points may be generated by photogrammetry, structured light scanners, or laser scanners to name a few.

Each scan from a laser scanner requires alignment such that all scans fit together like pieces of a puzzle to accurately recreate the object, surface, or scene that was measured. This process of aligning two or more laser scans together into one coordinate system is called registration. Software is typically required to perform this function either on board the laser scanner or as a post processing function.

A method of generating a 3D model or image by using light. Typical sources of light are visible and infrared. The light is structured into a pattern that is distorted when projected onto a 3D surface or object. A sensor determines the 3D position of each point based on the observed distortion.

An electronic and optical instrument used for angle and distance measurements. Total stations can be used for forensic mapping of scenes (e.g., data for traffic accident reconstruction, fire and explosion scenes). The theodolite is an optical component within the total station similar to a telescope that allows the measurement of horizontal and vertical distances at various angles. The EDM (Electronic Distance Measurement) unit measures the linear distance to an object.