Group: Alan, Steve, Amber, Tavake, and Zak
Data: GPS tracks collected by field trip student group = GPS_data / GPX files
To run: Click GISC401_Task1.ipynb, then click the 'Open in Colab' tab to fire it up.
Task 1 Summary: Spatial Analysis and Processing of GPS Data
During the GISC401 Cass Field Station field trip, nine GPX trajectories were gathered using My Track (Android) and myTrack (iOS). The data covers recordings from March 14-15, 2026. Raw timestamps in UTC were converted to NZDT (UTC+13) for local analysis. The files differ widely in point count, duration, distance, and recording resolution, indicating various device settings and recording patterns among the group.
Stop detection used a minimum duration of 120 seconds and a maximum diameter of 150 meters for all trajectories. The longest stop outside Cass Station was identified and its location determined through geodesic distance filtering relative to the station's coordinates. Elevation analysis retrieved the highest recorded altitude from the entire dataset.
Analysis of time deltas confirmed that all nine files exhibit variations in their recording intervals. These differences stem from various factors, such as GPS signal dropout, background OS scheduling on mobile devices, and differing configured logging intervals. To ensure accuracy, timestamp arithmetic used rounding of deltas to 0.1 seconds resolution before analysis, aligning the counts of unique Δt values with expected patterns. No actual duplicate trajectories were found — the only pair with shared resolution (A.gpx and E.gpx at 120s) was recorded on different calendar dates, confirming they are not duplicates.
Tracking resolution across the dataset varies from 3s in F.gpx to 1,800s in C.gpx, directly affecting path accuracy. Lower resolutions tend to underestimate distance and omit geometric details, especially on winding terrains. G.gpx, although with a high 5s resolution, captures only a partial trajectory, specifically a short hike at Cave Stream Scenic Reserve near Castle Hill, since logging stopped before departure. Such files should be used cautiously or excluded when assuming each represents a complete travel segment. This underscores that resolution and completeness of recording are separate data quality factors that require evaluation before analyzing movement trajectories.