The ornamental design for a globalpositioningsystemtracker, as shown and described.
FIG. 1 is a perspective view of a global positioning system tracker of my design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a sectional view of FIG. 3, taken along the line of VIII-VIII.
The broken lines in the drawings are directed to environmental structures and are for illustrative purposes only, and form no part of the claimed design.