Thursday, 10 April 2008

PIR-based Marauders Map

When we tell technically-minded people about Alertme, often their first question is "where are the cameras?" Well, there aren't any! For most situations, we think motion sensors do a better job.

There's a great illustration of the ways motion sensors are actually better than CCTV in this article on New Scientist's website. Its about how engineers at Mitsubishi's research labs in Cambridge, MA, used a network of simple Zigbee motion sensors to make a Marauder's Map, letting them monitor how people use and move around their building.

In the video, you can see how the PIRs let a single researcher monitor the whole building, with no need to intrude on everyone's privacy by blanketing the whole place with CCTV. In the locations where there is a CCTV record, the PIR data lets them search it much more effectively than they could otherwise.

CCTV often seems like the obvious choice for this sort of thing, but the problem with video is that machines find it difficult to understand and search, and it needs lots of costly equipment. PIRs on the other hand give an easy to understand 'someone's here' / 'nobody's here' message, are able to monitor a wider area, are very small and far more cost effective.

Of course, there are times when a picture is worth a thousand words, and being able to see whats going on in your home is exactly what you want. If you participated in our video survey, you'll already know we've been thinking about this. The consensus so far seems to be that you want a camera that works at night, doesn't have any wires, is easy to use, and is nice to look at. That's a tough specification, but we'll see what we can do!