GPS elevation data is often less accurate than its horizontal positioning data due to several intertwined factors. The satellite geometry used in GPS systems, which is optimized for horizontal positioning, doesn’t provide the same level of coverage for elevation. This results in larger errors in elevation data. Furthermore, atmospheric conditions can have a more pronounced effect on vertical accuracy. Variations in humidity, temperature, and ionospheric disturbances can delay the GPS signal, affecting its accuracy more in the vertical dimension.

Another significant factor is multipath errors, where GPS signals reflect off surfaces like buildings or rock faces before reaching the receiver. These reflections can distort the travel time of the signal, leading to inaccuracies, especially in elevation measurements. The quality of the GPS receiver itself also plays a role. Higher-end receivers with sophisticated processing algorithms and better antenna designs can provide more accurate elevation data.

Additionally, GPS systems calculate elevation relative to an ellipsoidal model of the Earth, which doesn’t perfectly align with the actual shape of the Earth’s surface. This discrepancy can lead to inaccuracies when GPS elevation data is compared to true ground level. Although the intentional degradation of GPS signals, known as Selective Availability, was turned off by the U.S. government in 2000, other system limitations and local factors can still impact the accuracy of GPS data, including elevation. Therefore, while GPS is a powerful tool for determining horizontal positions, its elevation data should be treated with more caution due to these various limitations.

Please be advised that the elevation data provided for Ironman Triathlon races has been compiled from various sources. While we strive to present the most accurate and up-to-date information, it is important to acknowledge that this data may contain inaccuracies. One key factor affecting the precision of elevation data is the known limitations of GPS signals. GPS-based elevation measurements can be less reliable than horizontal position data due to factors such as satellite geometry, atmospheric conditions, multipath errors, and the inherent limitations of GPS technology. Additionally, different GPS devices and methods of data collection can yield varying results. Therefore, we recommend that participants and interested parties consider these potential discrepancies when reviewing the elevation data for Ironman Triathlon races. Our team continuously works to refine and improve the data accuracy, but some level of uncertainty is inherent in such measurements.