Jitter (GPS/GNSS)

GPSGPSThe Global Positioning System (GPS) is a satellite-based navigation system operated by the U.S. Space Force that prov... jitter refers to the small, rapid, and seemingly random fluctuations in position readings reported by a Global Navigation Satellite System (GNSSGNSSGlobal Navigation Satellite System (GNSS) is the umbrella term for satellite-based positioning systems that provide a...) receiver, even when the receiver is completely stationary. These fluctuations are an inherent characteristic of satellite-based positioning and arise from multiple physical and environmental factors that introduce noise into the signal path between satellites and the receiver. Understanding and mitigating jitter is essential for any application that depends on precise or consistent location data, from fleet tracking and mobile analytics to surveying and autonomous navigation. Several distinct mechanisms contribute to GPS jitter. Multipath interference occurs when satellite signals bounce off nearby surfaces such as buildings, vehicles, or terrain before reaching the receiver antenna, causing the receiver to compute slightly incorrect distances to the satellites. Atmospheric delays, particularly in the ionosphere and troposphere, bend and slow the signals in ways that vary with solar activity, weather, and the satellite's elevation angle. Satellite geometry, quantified by the Dilution of Precision (DOP) metric, also plays a role: when visible satellites are clustered in a small portion of the sky, small ranging errors are amplified into larger position errors. Finally, clock errors in both the satellite and receiver oscillators introduce timing noise that translates directly into position uncertainty. In raw location data, jitter manifests as a scatter of position fixes around the true location. For a stationary device, this scatter may span a few meters under open sky or tens of meters in urban canyons. For moving devices, jitter can produce speed artifacts, making a parked vehicle appear to creep at low speed, or causing abrupt heading changes in trajectory data. These artifacts can corrupt downstream analyses such as trip detectionTrip DetectionTrip detection segments continuous streams of mobile device location data into individual journeys with defined start..., dwell-time calculation, and geofence triggering if left unaddressed. A range of mitigation techniques exist to reduce jitter's impact. Kalman filtering and its variants smooth successive position fixes by combining the noisy GPS measurements with a motion model, producing a more stable trajectory estimate. Satellite-Based Augmentation Systems (SBAS) such as WAAS in North America and EGNOS in Europe broadcast differential corrections that compensate for atmospheric and orbital errors in real time, improving accuracy to one to two meters. For applications requiring centimeter-level precision, Real-Time Kinematic (RTK) corrections use a nearby base station to eliminate most common-mode errors. Simpler approaches such as position averaging, where multiple fixes are collected and their mean is used, are effective for stationary applications like establishing a survey control point. It is important to distinguish jitter from drift, a related but different phenomenon. Jitter consists of high-frequency, random fluctuations that average out over short periods, whereas drift is a slow, systematic shift in reported position that persists over minutes or hours and is often caused by changing satellite geometry or unmodeled atmospheric conditions. Fleet tracking systems, mobile location analytics platforms, and geospatial dataGeospatial DataGeospatial data encompasses information about the location, shape, and relationships of physical features on Earth. I... pipelines must account for both effects to deliver reliable position data to end users and downstream models.