Table 1: Influence of different light intensity.

      Time period   Light condition       Detectable ratio
      05:30-06:30   Lamp       79%
      06:30-07:30   Natural light       81%
      07:30-08:30   Natural light       86%
      08:30-16:30   Natural light       96%
      16:30-17:30   Natural light       89%
      18:30-19:30   Lamp       81%
      19:30-05:30   Lamp       72%

Detectable ratio = Area that can be cleared framed / area of the whole chassis.