Short metal rods - about 3 m long, placed at the depth of not more than 0,5 m are often chosen when projecting grounding in the conditions of the Russian midland. Besides, rods of this length are enough in order to reduce the influence of freezing and drying of the ground on the grounding resistance. But in order to provide required values of grounding resistance, it is required to drive at least 3 rods into the ground. They are placed at the distance, approximately equal to the length of the rods. In the result, grounding occupies a significant area.
Grounding resistance is in reverse ratio to the area of electrode contact with the ground. It means several short rods can be substituted by one long, providing the summary length is considered. One of the main advantages of vertical ground electrodes is the use of minimal volume of space for organization of the grounding device.
You can read more about this and other advantages of this solution in the article "Why long vertical ground electrodes are required?"