To view sensor coverage category click on the lower right sensor coverage icon or press W. All areas covered by base sensors, team-mate sensors, deployable sensors, turret sensors, vehicle sensors etc. that are in the viewable map area will be displayed.

Green areas show base turret and mobile base sensor coverage
Gold areas show base sensor, deployable pulse sensor and Shrike AWAC sensor coverage
Blue areas show motion sensor coverage
Purple areas show deployable turrets sensor coverage.

If you see a sensor coverage circle that has 'broken' sections it is because sensor coverage in that section is blocked by by hills, objects etc.