Note: Take advantage of any reference lines on the infield, such as a soccer penalty box or football yardage lines. These will help your measurement line be as straight/perpendicular as possible.
Note: For simplicity/standardization our measurements are from the inner line/rail of lane one rather than the imaginary "measure line" in the IAAF rule book, which can be 10-30 cm out from the inner line of lane one.
Note: Zoom the map as far as you can while still keeping both inner edges of lane one in the window. This will make the precision as high as possible.