The reform program for upper secondary school stresses investigations. Along with the common class work students have to choose an applied mathematics subject for self-instruction and group work in a practical way, resulting in a report and a performance. Examples for different subject matters are already designed.'GPS and mathematics' is one of them about navigation with satellite assistance of the Global Positioning System (GPS). GPS principles (ranging and time, tri-distance-metry instead of tri-gono-metry, 2D and 3D navigation) and attractive pages of nearly every handheld gps were introduced to every student: 'Skyview' shows the heavens with satellites, 'Position' gives one's coordinates and 'Moving Map' is an electronic map. Students could stay in classroom doing tasks in chapters like 'GPS users are up', 'Imagine, you as a GPS receiver' and 'Consulting internet'. Some students, however, did take a field trip with a GPS receiver and carried out a small research. About the trip they made a report containing an overview of their activities and reflections on their experiences. They also investigated related subjects of which suggestions are given in the book, like: satellite orbit projections on the screen of the graphic calculator, using 'chart data' as ellipsoids. In short, students can be put to work in a meaningful application of their mathematical knowledge with the use of different instructional ways.