In the near future, first responders may become equipped with mobile devices providing navigation, decision and communication support. Because of the complex and chaotic circumstances in which these devices will be used, the devices should support the creation and maintenance of adequate situation awareness. Extensive testing of such devices for crisis management in real-life is expensive, complex, risky and only possible for specific settings. Therefore, we developed a synthetic task environment that is suited for developing and evaluating new concepts. In this paper, we present the results of the first experiment in this environment. Participants had to rescue victims in a synthetic world, and were supported by a map of the area showing the location and orientation of the participant and the victims. The experiment focused on the effects of map size and users spatial ability on the quality of the situational awareness that was developed by the first responders. Besides the results of the experiment, experiences with the use of a synthetic environment for evaluation and development purposes are presented.