Knowing firefighters’ locations in a burning building would dramatically improve their safety. In this study from the Saxion Research Centre for Design and Technology in the Firebee project, an algorithm was developed and tested to enhance the estimation of a person’s location, based on inertial measurements combined with measurements of the earth’s magnetic field. The developed algorithm is an extension of the zero velocity update technique. Without any enhancements, the accuracy of the estimation is in the order of several meters after measuring for only a few seconds. With enhancements, the accuracy improved to be within five meters after measuring for ten minutes. Our result demonstrated that it is possible to determine in which room and on which floor a person is after ten minutes. Major improvements were observed in the estimation of the sensor’s height. The results are promising and the following phases of the project focus on improving the solution and on developing the concept into a practically applicable system.