Intrusion Zones and Tripwires: How They Are Set Up

You have been told a camera can notify you when someone enters a certain area. How does it know where the area is? Someone draws it on the picture. Where and how that is done decides whether the alerts are useful or a nuisance.

Two tools, two jobs

An intrusion zone is a virtual area drawn inside the camera image. The system flags when a person, or another selected object type, enters it. Example: notify me if a person enters this area after business hours.

A tripwire is a virtual line. The system detects when a person or vehicle crosses it. It suits entrances, driveways, gates and restricted areas.

Both are available on compatible systems, and AI features vary depending on the selected camera and recorder. Entry-level systems may offer basic motion detection only. Check the model first, as covered in the AI features guide.

When to use which

In many installs both are used on the same camera. The question to ask is whether you care that something is present, or that something crossed.

How zones and lines are drawn

The process is straightforward, even though the screens differ between models.

1. Open the camera's view in the recorder or its settings.
2. Choose the detection type, for example intrusion or tripwire.
3. For a zone, click points on the image to outline the area. For a line, mark the two end points. Some systems let you choose which direction counts.
4. Select what triggers it, such as a person, a vehicle, or both, where supported.
5. Set a schedule so the rule is active only when you want it.
6. Choose the action. That might be a notification through DMSS, recording, or both.
7. Save, then test.

An installer will usually do this on site, because the view of the real scene helps with every decision below.

Placement and angle

The picture is a flat image of a three-dimensional space, so placement affects results.

• Draw the zone on the ground, not the sky. A zone covering the horizon or a tall fence may react to things beyond your boundary.
• Keep it away from busy edges. A zone touching a footpath will trigger for every walker.
• Leave a margin. If the zone starts exactly at the doorway, a person is already inside when the alert fires. Starting a little earlier gives more notice.
• Mind the distance. Objects far from the camera appear small and are harder to classify. The field of view tool helps you picture coverage.
• Aim for an angle that sees the person. A camera looking straight down at a head may do worse than one at a modest downward angle. Camera height and tilt matter. See where to place cameras.
• Avoid glare. Direct sunlight, headlights and bright reflections degrade the image.

A worked example

A house has a side path leading to the backyard. The installer places a camera at the corner of the house looking down the path. A tripwire is drawn across the path about a third of the way along, so a person is flagged on entering and before reaching the back door. A zone covers the lawn, active overnight only. The tripwire alerts person-only, so a neighbour's cat does not trigger it. Notifications go to DMSS on the owner's phone.

That is two simple rules, each with a purpose, rather than a screen full of overlapping boxes.

Testing

Test after setup and whenever something changes.

1. Walk through the zone or across the line at normal speed, then slowly.
2. Try from each approach direction.
3. Test in daylight and at night if the rule runs overnight.
4. Check the notification arrives on the phone.
5. Check the recorded clip includes the lead-up.
6. Ask someone else to walk it, so you can watch the alert from the phone.

Re-test after trimming plants, moving objects or changing the camera angle.

Common mistakes

• Zones that are too big. More area means more false alerts.
• Zones that include public space. Footpaths and roads are rarely what you meant to monitor. This also raises privacy questions. See signage, privacy and neighbours.
• Lines drawn where people loiter. A line near a busy doorway is crossed constantly.
• No schedule. The rule fires all day.
• Never testing. An untested rule may do nothing at all.
• Forgetting the camera moved. A knocked camera shifts the picture, but the zone stays where it was drawn.

Limits

Detection can miss events or flag the wrong thing, especially in poor light, at distance or with partial obstruction. Zones and lines help the system flag events. They do not guarantee detection. A person decides what the alert means.

If you want help planning positions, you can ask us about installation. The glossary defines terms like field of view and false alarm.

Frequently asked questions