The fields of view must be in descending order as the view level increases - level 3 must have a smaller field of view than level 2; level 4 must have a smaller field of view than level 3, and so on.
The fields of view must be in descending order as the view level increases - level 3 must have a smaller field of view than level 2; level 4 must have a smaller field of view than level 3, and so on.
观察的视场范围是按视场等级的降序排列的——3级视场肯定要比2级视场小，4级视场又会比3级视场小，以此类推。