What our experts say…
Video motion detection has become something of a black art, with many varying claims made for its effectiveness. However, while our eyes and brains can discriminate between innocent natural motion (trees blowing in the wind, sudden changes in lighting level, shadows and small creatures) and genuine targets in a fraction of a second, it is a fantastically difficult feat for a machine.
Even powerful state-of-the-art supercomputers can get into trouble. So what new slant does the Visimetrics Pathfinder bring to the proceedings?
It is obviously not a supercomputer but it is a stand-alone unit, which is unusual. Video motion detection systems are normally integrated into other video surveillance devices, such as multiplexers and recorders. This one is housed in a slim rack mountable case, and one of the first things you notice is the absence of any controls and just a handful of LED indicators on the front panel.
There is not a lot to see around the back either, just a bank of BNC sockets for video input, loop-through and monitor displays, each with a simple jumper/shorting link for setting termination. There is a screw-terminal for alarm connections, a nine-pin D-Sub serial port and a standard DC supply socket. A 12 volt mains adaptor module is supplied. Two versions are available with two and four camera inputs; our test sample was the four-channel model.
Needless to say all is not as it seems and there is plenty going on behind the scenes. Key features include variable sensitivity, zone masking using a 32 x 32 target grid, visible target overlay, camera sequencer/alarm display, separate relay alarm outputs for each channel, and the unit can be set to temporarily ignore ‘movement’ when using PTZ cameras. The front panel indicators show power on, connected cameras and alarm triggers.
Set-up & operation
As the lack of controls suggests, Pathfinder can be used straight out of the box without any configuration, though it is unlikely many installations can operate reliably on the default settings, in which case it is necessary to access the unit’s configuration settings. That is where the serial port comes in: access to Pathfinder’s inner workings requires a PC, typically any Windows PC, but it must have a standard serial port connection which is becoming increasingly rare on laptops these days.
The access software, called Pathfinder Terminal, is supplied as a compressed Zip file on a 3.5-inch floppy disk (so make sure you have an unzip utility like WinZip on your control PC). Once the file has been extracted Pathfinder Terminal can be launched. The first thing it does is attempt to communicate with the Pathfinder, which may entail editing the Com Port settings.
Once the link has been established the current settings stored in the unit are read and displayed on a simple dialogue box display with five function buttons. From left to right they are: Read Settings, Write Settings, Load Defaults, Connection and Mask Editor.
Read Settings is divided into two areas: the top half of the screen shows each of the camera channels, with the facility to change the name or title for each camera (only shown on the PC display). To the right of each camera there is an enable/disable tick box, and two value adjustments for setting Minimum Object Size in pixels (from 1 to 4096, default 15), and Consecutive Frames (0 to 32767, default 3). The latter specifies how many frames of video a moving object must appear in before it is deemed to be a genuine target.
Between them, Minimum Object Size and Consecutive Frames can be used to accurately eliminate many predictable and naturally occurring false targets. The lower half of the Read Settings box is called Hold Times and is used to adjust various alarm timing parameters, including video on, relay on, alarm LED on and target box display.
The Write Settings button sends the revised data back to the unit, Load Defaults restores factory settings and the Connection button brings up dialogue boxes for changing Com settings, rebooting the Pathfinder and disconnecting the PC. The Mask Editor button launches a simple graphics utility that allows the user or installer to mask selected areas of the image.
However, the Editor box is initially blank and a low definition still is loaded into the frame by clicking the Read Mask button. Clicking New Mask on the drop-down menu changes the cursor into a pen icon and areas of the screen can be defined. The utility also contains a small selection of drawing tools, for defining square and circular shapes and for filling them in.
When the masking is complete all that remains is to click the Write Mask button to update the Pathfinder. The well-written instructions helpfully point out that zone masks should not be set for PTZ cameras, along with lots of other useful tips for camera positioning and configuration.
Performance
Video passes more or less straight through the Pathfinder. The only significant change occurs on the Overlay output, which superimposes a white ‘target’ square on a moving object, and tracks with it as it travels around the screen. The system can only cope with one moving object per channel, which could be an advantage or a drawback.
Target acquisition and tracking are generally fast and accurate but ultimately it depends on the quality of the image and the care taken in setting it up. Nevertheless, for simple situations – detecting movement in normally unoccupied areas, corridors and perimeters etc – it may indeed require little or no configuration.
What the manufacturer says …
Pathfinder is an intelligent video motion sensor system for CCTV installations, providing reliable detection of people and vehicles moving within the camera scenes. Unlike traditional video motion detectors with their complex set-up procedures, Pathfinder simply requires the cameras to be connected to complete the installation. Pathfinder automatically ignores most environ-mental movement such as moving foliage backgrounds and lighting changes caused by rain and clouds.
Pathfinder provides alarm signals which are used to alert guards, start recording or switch to video displays.
A video loop-through is provided for each video channel, allowing Path-finder to be connected in series with monitors, switchers, recorders etc.
Each channel also has a separate video output with graphic overlay for displaying the position of objects detected in the scene.
A further benefit is the provision of a 4:1 switched video output channel. This displays either a fixed camera sequence (1, 2, 3, 4) or a blank screen and automatically switches to display any channel where motion is detected. Multiple alarms are displayed in sequence.
Pathfinder can even be used with pan/tilt/zoom cameras. It ignores the apparent movement due to PTZ actions, and resumes detection in the new scene after the camera comes to rest.
