translate English to French: Although the same circles are usually covered year after year, there are no rules governing their placement, the number or skills of observers,or time spent in the field.
Les mÃªmes superficies sont gÃ©nÃ©ralement couvertes chaque annÃ©e, mais il n'existe aucune rÃ¨gle rÃ©gissant leur emplacement, le nombre ou l'aptitude des observateurs, le temps passÃ© sur le terrain, etc.