| BG |
Broad Gauge (1676 mm), the standard rail gauge in India |
| Block |
A reserved section of track cleared for inspection/maintenance |
| Cross-level |
Relative height difference between left and right rail |
| DAQ |
Data Acquisition — the pipeline capturing sensor data |
| Format C |
Indian Railways standard track geometry output report format |
| Gauge |
Distance between inner faces of rail heads, measured 14 mm below rail top |
| GNSS |
Global Navigation Satellite System (GPS, GLONASS, etc.) |
| iceoryx |
Zero-copy IPC middleware used in the DAQ pipeline |
| IMU |
Inertial Measurement Unit — measures acceleration and angular velocity |
| IRPWM |
Indian Railway Permanent Way Manual |
| MCAP |
Open-source file format for multimodal sensor data recording |
| Mission |
A single inspection run, identified by a unique mission_uid |
| OHE |
Overhead Equipment — the electrification system above the track |
| P.Way |
Permanent Way — the railway track structure |
| PWI |
Permanent Way Inspector — the Indian Railways official responsible for track |
| SSE |
Senior Section Engineer |
| TGIS |
Track Geometry Inspection System (generic term) |
| TRC |
Track Recording Car — Indian Railways' existing inspection vehicle |
| Twist |
Rate of change of cross-level over a defined base length |
| Unevenness |
Vertical profile irregularity of the rail |
| Versine |
Lateral deviation measured as mid-chord offset |