Motion relative to the ground is typically measured using a reference frame, which is a system of coordinates and time used to describe the position and movement of an object.
The speed of an object relative to the ground is affected by various factors, such as its own velocity, the velocity of the ground, and any external forces acting on the object.
The curvature of the Earth does not have a significant impact on an object's speed relative to the ground, as the Earth's surface is relatively flat compared to the size of most objects and their movements.
Yes, it is possible for an object to have a constant speed relative to the ground if it maintains a consistent velocity and there are no external forces acting on it.
The rotation of the Earth can have a small effect on an object's speed relative to the ground, as the Earth's rotation causes a slight change in the velocity of objects at different latitudes.