Buildings affect your visibility to Sensor Sweep.

Industry_detection_chance =
   0%            ...if Mines < MinesForDetectable
                    and Factories < FactoriesForDetectable
   0%            ...if Defense ≥ DefenseForUndetectable
   100% - (Defense / DefenseForUndetectable * 100%)
                 ...in all other cases

Industry_level_reported =
   "minimal"     ...if (Mines + Factories) < 30
   "light"       ...if (Mines + Factories) < 60
   "moderate"    ...if (Mines + Factories) < 90
   "substantial" ...if (Mines + Factories) < 120
   "heavy"       ...if (Mines + Factories) ≥ 120

Bioscan_detection_chance =
   0%            ...if Defense ≥ 20
   0%            ...if ship does not have bioscanner (of course :-)
   100%          ...if ship has full bioscanner
   20%           ...otherwise
This is a testing version.
It may be incomplete, and have more bugs (or features) than the public live version at planetscentral.com.