Eliminating CCTV Blind Spots: The Complete Coverage Guide
A blind spot is any area within the site boundary that no camera can observe at the required DORI tier. Blind spots are inevitable in every layout — the goal is to find them at design stage, reduce them to an acceptable level, and document the residual gaps before the client does. This guide covers the six sources of blind spots and how the free CCTV Design Tool helps eliminate them.
Open the free CCTV Design Tool →
1. The six types of CCTV blind spots
| Type | Cause | Detection method |
|---|---|---|
| 1. Coverage gap | No camera aimed at the area | Heatmap reveals white/red zones |
| 2. Dead zone | Area directly under a camera mount — invisible to every lens | Heatmap shows a red circle around each camera |
| 3. Wall/obstacle shadow | Solid object blocks the FOV cone | Wall-aware clipping highlights shadow in red |
| 4. Tier gap | Area is covered, but below the required DORI tier | DORI overlay shows the tier at every point |
| 5. Motion blur | Moving subject blurs below recognition threshold | People/vehicle simulation highlights the drop |
| 6. Environmental | Backlight, IR washout, or weather occlusion | Field survey — not simulatable |
2. The dead zone problem
Every camera has a dead zone immediately beneath its mounting position. A camera at 4 m height with a 70° HFOV and level tilt cannot see the ground for the first 2.5 m directly below it. This is not a design flaw — it is physics. Plan overlapping FOVs from adjacent cameras to cover each other's dead zones.
3. Coverage overlap targets
Industry best practice (BS EN 62676-4) recommends:
- Identification zones: overlap by at least 25 % (redundant coverage if one camera fails)
- Detection zones: overlap by 10–15 % to eliminate corridor gaps
- Perimeter zones: overlapping FOVs from opposite directions to capture front and rear views of intruders
4. How the tool eliminates blind spots
The free CCTV Design Tool runs a full-coverage blind-spot analysis in one click:
- Every camera's FOV cone is calculated at true scale from its model's HFOV, mounting height, and tilt
- Walls, doors, columns, and landscape obstacles clip FOV cones in real time — no phantom coverage through concrete
- The heatmap overlay colour-codes every square metre: green = covered at required tier, amber = partial, red = blind spot
- A coverage percentage score lets you compare layouts quantitatively
- Blind-spot area in square metres is reported in the PDF export for audit trails
Launch the free tool →