We need to optimize Smartphone GPS positioning. Our award-winning app. developed in React Native, on iOS and Android, calculates speed, during walking or running outdoors, based on GPS. In some cases, the measured speed is wrong

We need to optimize our award-winning app developed in React Native on both iOS and Android to ensure more accurate GPS positioning results for our users. We built it with the aim of providing them with an accurate measure of their fitness level leveraging, among other, speed during walking or running outdoors, however we have experienced issues with GPS where the calculated speed is sometimes wrong. We would like to ensure that the measurements are within 0.3 to 0.5 Km/h accuracy. To ensure this level of accuracy, we are open to implementing additional technologies or methods to improve GPS positioning accuracy which would also be beneficial to our users. We invite experts to work with us and optimize our app to give our users a beautiful and accurate experience.