**3.3. Terrestrial laser scanner**

documentation of indoor scenes is done, the Cartesian reference system is characterized by the fact that the Z axis tends to coincide with the vertical direction and *XZ* (or *YZ*) plane usually matches to some of the façades or walls object (if there is possible, on the contrary it could be arbitrary). The positioning of each photograph in space is determined by the three spatial

Finally, the reconstruction of the object is performed through the intersection between different correspondent and perspective lines (collinearity condition) by using at least two photographs. In geometric terms, this means a difficult task, especially in those cases where a full automation is required. To solve this problem, photogrammetry, without prior knowl‐ edge of the object, acts similar to the behaviour of human vision, in which images are obtained

In this subsection, we want to focus on panoramic images and virtual tours. In spite of the difficulties to take measures in panoramas, they have an extraordinary capability to organize spatial information in qualitative terms, which is essential to describe hypothesis in forensic

Unlike conventional photography, in which a detail or a particular frame in the scene is shown, panoramic images have the property to collect the whole graphic information, covering a large angular field of view [9]. Thus, it is intended to get the feeling of being in the scene. The immersive experience can be achieved on a 360° field of view basis, greater than the human

With the advent of digital age panoramic photography has boomed and multiplied its possible applications. Digital technology increases the flexibility of these documents to be altered, enhanced, rescaled, processed, resampled or fused in a 'simple' way. Computers are able to show the part of the panoramic picture corresponding to any direction and display it in real time. Thus, the feeling of a natural sweep through the panoramic image, which simulates

Panoramic images can be projected on flat, spherical, cylindrical or cubic surfaces (**Figure 5**). To do this, it has to be solved the classic problem of mapping, which gives the optimal solution

Panoramic images are on the basis to create virtual tours. This is an interactive non‐metric product of that allows travelling through complex scenarios, making virtual check and supervision. They also permit the addition of extra information in a various formats (text, photos and multimedia resources) that are accessed interactively. Virtual tours are integrated into a compact interface in which an interactive map acts as a guide to explore and travel

One of the strengths of the panoramic photography and virtual tours is its portability. In the end, panoramas are standard digital images; virtual tours only need flash viewers or html5

to represent on a flat support (either paper or digital) the surface of the Earth.

coordinates (*X*, *Y*, *Z*) and the three spatial angles (ϖ, ϕ, χ) of the viewpoint.

from two converging intersections.

10 Forensic Analysis - From Death to Justice

research.

eye can see in an instant.

through the single panoramas.

support (built‐in web browsers).

**3.2. Panoramic images and virtual tour**

plausibly turns to the viewer's head, is created.

TLS is a non‐invasive measuring instrument, whose use began to spread in the late 1980s. It produced many changes, not only in planning, but in the development and implementation of 3D projects [10]. It came as an adaptation of the previous aerial laser scanning (ALS) and LiDAR (light detection and ranging) systems. Using TLS in 3D reconstruction of small crime scene or large area disasters is a powerful line of work in forensic engineering. The simplicity and visual effectiveness of graphics obtained directly in data acquisition phase should not hide the complexity of further discrimination and categorization processes, absolutely necessary if we want to accomplish the forensics' requirements. The massive and automatic capture of 3D metric information is its main and advantageous feature. Unlike other technologies, in which operators only select the most significant points in order to geometrically define the scene, TLS is based on the concept of 'blind' and complete measurement by means of using an active sensor able to acquire millions of points in just a few seconds.

TLS acquires point clouds: a set of three‐dimensional points on a Cartesian system. In addition to *X, Y*, *Z* coordinates, in every single point, it will be added some attributes (additional information), such as its radiometry (RGB values of colour), its intensity.

There are several physical principles on which this TLS technology is based, and there are also many different brands, models and built on solutions provided by manufacturers. That implies that there is not standard TLS equipment able to solve all the forensics' requirements (meas‐ urement accuracy, distance range, radiometry detection, angular capability, etc.). By contrast, forensic users have to assess the features and performance of the TLS so that they fit their requirements.

Given the physical basis underlying the measurement of distances TLS can be classified into three groups: flight time, phase shift and an optical triangulation (**Figure 6**).


**Figure 6.** Measurement principles of TLS systems. Time of flight (a); phase shift (b) and optical triangulation (c). Im‐ ages courtesy of Leica, Faro and Artec respectively.

In order to choose the appropriate equipment, it must be considered the best balance between accuracy, completeness, resolution, and timing in data capture and processing.
