The use of dGPS and simultaneous metabolic measurements during orienteering

The Global Positioning System (GPS) is a satellite-based system for navigation. With this system, it is possible to pinpoint a subject's location on earth and to display the speed of movement. With the use of differentiation (dGPS), the accuracy of the GPS position and speed measurements can be improved. Our purpose was to investigate whether it would be possible to relate dGPS data with physiological variables in a field test and thus achieve a more controlled field test and hence improve the value of sport-specific testing.

10 male orienteers were equipped with a portable metabolic gas analyzer and a differential Global Positioning System (dGPS). A field test was performed on a 4.3-km orienteering course. Oxygen uptake, carbon dioxide excretion, and heart rate were determined every 10 s. Speed was calculated by Doppler shift every 2 s and by differences in dGPS time and position. Validation of dGPS position, distance, and speed measurements was made on two fixed positions and on a 115-m straight asphalt road.

The orienteers' route was visualized by the dGPS equipment. Detailed analysis of running speed in different sections of the course was made possible. Further, it was possible to relate each physiological data to the location of the subject. The correlation coefficient between speed measured by dGPS and speed measured by chronometry was r = 0.9995-0.9996. The mean errors of distance and position measurements were 0.04-0.7% and 1.94-2.13 m, respectively.

dGPS was shown to be a method that could give detailed information about a subject's speed and position. It was further demonstrated that physiological variables could be related to dGPS data.