All companies that use GPS systems for fleet management eventually ask why there's a difference in mileage between the speedometer readings and the GPS system data. The mileage recorded in driver logbooks also often differs from the GPS monitoring system's report. We've conducted a thorough analysis of this issue and are ready to explain why these discrepancies occur and what percentage of deviation is considered acceptable.
Why Do Mileage Readings Differ?
Discrepancies in mileage data are a common phenomenon caused by a combination of technical and operational factors. Understanding these reasons will help you correctly interpret the data and make informed management decisions.
Key factors influencing data discrepancies:
- Speedometer Calibration: Speedometer readings depend on factory settings, wear and tear, and, most importantly, the size of the tires installed. Even a slight change in wheel radius can lead to noticeable errors in readings.
- GPS Tracker Operation Principle: GPS systems determine location by coordinates at a specific frequency (e.g., every few seconds). Mileage is calculated as the sum of distances between consecutive points.
- Trajectory "Smoothing": With infrequent recording intervals or an unstable signal, GPS may "cut" corners, failing to account for all minor maneuvers, turns, or obstacles, leading to underestimated mileage compared to the speedometer.
- Road Unevenness and Maneuvers: A speedometer accounts for every wheel rotation, including those occurring over uneven surfaces, minor maneuvers, or wheel slippage. GPS, on the other hand, only measures the linear displacement of an object.
- External Conditions: GPS signal interference (e.g., in dense urban areas – "urban canyon," tunnels, forests) can temporarily impair positioning accuracy, causing false coordinate "jumps" and mileage distortions.
- Human Factor: Errors in filling out logbooks or even intentional distortions by drivers can cause discrepancies with GPS data.
Acceptable Deviation Percentage: Norm and Reality
A complete absence of discrepancies between the speedometer and GPS is virtually impossible. It's crucial to understand what percentage of deviation is considered acceptable and doesn't raise concerns.
What is considered the norm?
- Typically, a deviation in the range of 1% to 3% between speedometer readings and a GPS monitoring system is considered acceptable in most cases.
- Under certain conditions (e.g., driving on complex routes with frequent stops, poor GPS signal), this percentage might be slightly higher, reaching up to 5%.
- Factors influencing the "norm": vehicle type, route characteristics (city, highway, off-road), quality and settings of GPS equipment, and its regular maintenance.
How to determine acceptable discrepancies for your company?
- Conduct test drives: Perform several test trips on known routes, comparing speedometer and GPS readings.
- Analyze long-term data: Systematically compare data across your entire fleet to identify average deviation percentages and anomalies.
- Consult with specialists: GPS monitoring experts can help configure equipment and determine optimal parameters for your specific needs.
Impact of Inaccuracies on Business and How GPS Monitoring Helps
Inaccurate mileage and fuel consumption accounting can have serious consequences for a company's budget and efficiency.
Consequences of inaccurate accounting:
- Fuel Overconsumption: The most obvious and costly problem, leading to significant financial losses.
- Planning Errors: Inaccurate data hinders effective route planning, logistics, and workload distribution.
- Incorrect Working Time Accounting: Difficulties in calculating salaries and adhering to driver labor standards.
- Reporting Issues: Discrepancies can raise questions from regulatory bodies.
Advantages of professional GPS monitoring:
- Objective Control: The system provides accurate and independent data on mileage, speed, routes, and fuel consumption, eliminating the human factor.
- Resource Savings: Helps identify inefficient routes, deviations, unauthorized trips, and fuel siphoning, leading to significant savings.
- Logistics Optimization: Automated reporting and analytics enable optimal route planning and efficient fleet management.
- Transparency: All data is accessible at any time, ensuring complete control and transparency of operations.
Conclusion
Understanding the reasons for mileage discrepancies and controlling acceptable deviations are critically important for effective fleet management. Modern GPS systems not only track vehicles but also significantly improve accounting accuracy, leading to substantial savings and optimization of business processes. Investing in a quality GPS monitoring system pays off through increased efficiency and reduced operational costs.