Ground Speed calculation requires you to be outside of what range?

Ground Speed calculation requires you to be outside of what range?

• A. Slant range
• B. Line-of-sight range
• C. Radar range
• D. Glide range

Answer: (A)

Ground speed is your horizontal motion over the ground, and when you estimate it from how quickly the distance to a ground beacon changes, you’re using the slant range—the direct line distance from you to the beacon. The relationship between the change in that distance and your actual horizontal speed only stays reliable once you’re far enough away that the line of sight is nearly horizontal. If you’re close to the beacon, the line of sight is steep, so moving horizontally changes the slant range by a much smaller amount than your true ground speed, giving a distorted result. So to get a valid ground speed from range changes, you need to be outside of the slant range.

Ground speed is your horizontal motion over the ground, and when you estimate it from how quickly the distance to a ground beacon changes, you’re using the slant range—the direct line distance from you to the beacon. The relationship between the change in that distance and your actual horizontal speed only stays reliable once you’re far enough away that the line of sight is nearly horizontal. If you’re close to the beacon, the line of sight is steep, so moving horizontally changes the slant range by a much smaller amount than your true ground speed, giving a distorted result. So to get a valid ground speed from range changes, you need to be outside of the slant range.