Quantifying Distance Overestimation From Global Positioning System in Urban Spaces.

Area of Science:

• Geographic Information Systems (GIS)
• Spatial Analysis
• Urban Planning

Background:

• Global Positioning System (GPS) technology is widely used for tracking movement and inferring travel behavior.
• Accuracy of GPS-derived distance measurements can be affected by environmental factors, particularly in complex urban settings.

Purpose of the Study:

• To evaluate the accuracy of distance measurements calculated from GPS data in New York City.
• To determine the influence of urban environmental factors, such as building height and tree canopy cover, on GPS distance accuracy.

Main Methods:

• Structured walks were conducted in areas with varying building heights and tree canopy cover using GPS data loggers.
• Distances were computed using both straight-line (GIS-measured) and cumulative waypoint (GPS-measured) methods.
• ArcGIS software was utilized for walk selection and distance computation.

Main Results:

• GPS-measured distances significantly overestimated actual distances, especially in areas with high building height (median 97% overestimate) compared to low building height (14%).
• Higher tree canopy cover also led to increased GPS distance overestimates (43% for high vs. 28% for low).

Conclusions:

• The accuracy of GPS-derived distances is compromised in urban environments with significant building height and tree canopy.
• Algorithms relying on GPS distances for inferring speed or travel mode may introduce systematic errors, leading to misclassification of trips.
• Researchers should consider alternative methods for travel mode identification in urban studies due to GPS inaccuracies.