The performance of indoor positioning systems is usually measured by their accuracy in meters. This facilitates the comparison of different systems, but does not necessarily give information about how well they perform in real-life scenarios, e. g. during indoor navigation of walking persons. In this paper, we present a task-oriented evaluation that adapts the idea of landmark navigation: Instead of specifying the error metrically, system performance is measured by the ability to determine the correct segment of an indoor route, which in turn enables the navigation system to give correct instructions. We introduce the area match metric in order to identify areas where positioning proves problematic. In order to evaluate the described metric, we use a pedestrian dead reckoning approach to compute indoor positions. Without any external correction, the correct segment of the test route is identified in 88.4% of all trials. Based on these results, we explore options how to identify and predict erroneous situations during the navigation process as well as beforehand.