# Comparative Analysis of LiDAR and Photogrammetry for 3D Crime Scene Reconstruction
## 3 Methodology
### Model 2: Photogrammetry with PiX4 Dcatch and Pix4 Dmapper  
The photogrammetry approach was conducted using Pix4 Dcatch, which is designed to automatically capture images through the phone. It is installed on the iPhone 15 Pro Max to ensure consistency between the models. The application collects the images that will be used to reconstruct the 3D models using Pix4 DMapper. The data collection phase involved scanning the mock-up crime scene with four scenarios. The same person conducted all scans  
\begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Model** & **Device** & **Technology/Application** & **Purpose of Use** & **Scanning Duration** & **Illumination Conditions** & **Key Differences** \\ \hline \multirow{3}{*}{Model 1} & iPhone 15 Pro Max & \multirow{3}{*}{LIDAR, Recon-3D App} & To create 3D models using a built-in iPhone & \multirow{3}{*}{Five/Ten Min.} & \multirow{3}{*}{Day/Night} & Utilizes LiDAR \\  & & & & iLDAR scanner and & & & for portable \\  & & & & Recon-3D app. & & & and quick \\ \hline \multirow{3}{*}{Model 2} & iPhone 15 Pro Max & \multirow{3}{*}{Pix4 Dcatch, Fix4 Dmapper for} & To perform & & & \\  & & & photogrammetry & & & & \\  & & & and generate 3D & & & & colours, \\  & & & models from images & & & depending on \\  & & & & captured using & & & image quality \\  & & & & Pix4 Dcatch. & & & and lighting \\ \hline \multirow{3}{*}{Model 3} & Leica BLK360 & \multirow{3}{*}{LiDAR Scanning.} & To use a & \multirow{3}{*}{Ten Min.} & \multirow{3}{*}{Day} & High precision in \\  & Generation (Leica & & professional & & & 3D \\ \cline{1-1}  & Geosystems Inc., & & grade LIDAR as a & & & & reconstruction, \\ \cline{1-1}  & & & baseline reference. & & & less sensitive to \\ \cline{1-1}  & & & & baseline reference. & & & lighting conditions. \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary the scanning models for LiDAR, photogrammetry, and ground reference.  
to ensure consistency in data collection. The first scan was conducted under daylight, with 10 min allocated for the scanning process. The aim was to establish a baseline for daylight scanning efficiency and reconstruction accuracy. The second scan was conducted under the same daylight conditions, while the scanning duration was reduced to 5 min. The third scan aimed to assess the 3D model under nighttime conditions using only the built-in flash. Also, the scanning duration was 10 min, as the first scan was used to compare the impact of the lighting condition upon the 3D models between the third and the first scan, considering that the duration was constant for both scans. The fourth scan was conducted under the same lighting conditions as the third at night. The scanning duration was reduced to 5 min to assess the impact of the scanning duration upon the model under the same lighting conditions. Each scan followed a structured approach, involving three rounds of circular motions in overlapping paths around the scene to capture the scene from multiple angles: (1) medium distance, 2-3 ft away from the target, providing a balanced scene perspective; (2) closer distance to the ground to capture details closer to the surface; and (3) higher distance using a selfie stick to ensure complete coverage. After completing the scanning processes, all data were collected through Pix4 Dcatch, including the captured photos, metadata, and location data. They were exported as a ZIP file and processed through Pix4 DMapper to reconstruct the 3D models. The resulting point clouds were then exported in LAS format, so that CloudCompare software was utilized for point-wise evaluation.