## 3 The DELTA Platform  
In this section, we introduce the DELTA platform (depicted in Figure 2) which is specifically engineered for collecting a multimodal dataset targeting urban areas often neglected in typical urban studies. The platform is based on a modified electric scooter equipped with a comprehensive array of advanced sensors, enabling it to capture a wide range of environmental data from pedestrian pathways and sidewalks--spaces that are typically underrepresented in data collections.  
At the heart of this system is a high-precision GNSS/IMU unit, essential for accurate location tracking and motion data, which are critical for precise mapping and effective data integration. For visual and spatial data acquisition, the platform includes a ZED2i stereocamera and a 360-degree Ouster LiDAR, allowing for an extensive and detailed capture of environmental features. This is complemented by a 4K monocular camera and a stereo audio recorder, which augment the dataset with rich visual and auditory data. The specifications of the platform's sensors are detailed in Table 1. Data processing is efficiently handled by an NVIDIA AGX Orin module serving as the central processing unit. The system is mounted on multiple damping and vibration isolation systems to minimize noise and vibrations as much as possible to maintain the integrity of the data collected. Furthermore, its modular design also allows for easy customization to meet diverse research requirements, significantly broadening the platform's application in various urban studies.  
Integrating these high-precision sensors onto a singular mobile platform significantly enhances its utility in urban data analytics, particularly in the realms of mobile robotics and micro-mobility services. This setup is pivotal for analyzing pedestrian traffic patterns, supporting the development and upkeep of urban infrastructure, and optimizing the efficiency and safety of mobile robotics and micro-mobility solutions in complex city environments.  
Figure 2: Our multi-sensory mobile capturing platform followed by the coordinate system for each sensor setup.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Sensor (Manufacturer)** & **Details** \\ \hline Stereocamera (Stereolabs, Paris, France) & Dual 1/3\({}^{\prime\prime}\) 4 MP CMOS \\  & FOV: 110\({}^{\circ}\) (H) \(\times\) 70\({}^{\circ}\) (V) \(\times\) 120\({}^{\circ}\) (D) \\  & Range: 0.3 m to 20 m \\  & Gyroscope, Accelerometer \\  & Magnetometer, Barometer, Temperature. \\  & Resolution: (720 \(\times\) 405) 32-Bit. \\  & Frame Rate = 58 FPS \\ \hline LiDAR (Ouster, San Francisco, CA, USA) & Resolution: (1024 \(\times\) 64) 32-Bit \\  & FOV: 360\({}^{\circ}\) \\  & Range: 200 m \\  & Sampling frequency: 10 Hz \\ \hline Action Camera (DJI, Shenzhen, China) & 4K (4096 \(\times\) 3072) \\  & Frame Rate = 30 FPS \\  & FOV: 155\({}^{\circ}\) \\  & Audio Sampling Frequency: AAC 48.0 kHz \\ \hline Audio Recorder (Tascam, Tokyo, Japan) & Built-in cardioid condenser stereo pair \\  & Sampling frequency: 96 kHz/24-Bit \\ \hline IMU (WitMotion, Shenzhen, China) & Acceleration, Gyroscope, Magnetometer \\  & Angle (X, Z-axis: \(\pm\)180\({}^{\circ}\), Y \(\pm\)90\({}^{\circ}\)) \\  & Sampling frequency: 100 Hz \\ \hline GNSS module (u-blox, Thalwil, Switzerland) & Receives both L1C/A and L2C bands \\  & PVT (basic location over UBK binary protocol) \\  & Horizontal accuracy of 1.11 m \\  & Sampling frequency: 2 Hz \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sensor specifications of our platform.