The Sighthound Edge Analytics service/application allows you to configure virtual count sensors to report the count of a specific type of object (vehicles, people, etc.) going across a specified line. As objects cross, the direction of the object will be reported and the purpose of this document is to explain how each direction is defined.

As you add a count sensor using the Sighthound Platform configuration tool, you’ll notice that there are configuration options for “Clockwise label” and “Counterclockwise label”:

These labels will be used for objects crossing in the clockwise/counterclockwise direction. The clockwise direction will be determined by the way in which the count line was drawn. Specifically, the start point of the line will be the pivot point of an imaginary clock arm and the direction of clockwise will be dependent on this pivot point.

For example, if we have a diagonal line that is drawn from top-left to bottom-right, as shown below, we know that the top-left is the pivot point (think of an hour clock arm between hour 4 and 5). This means that any object crossing from top-right to bottom-left will be going in the clockwise direction, and vice versa.

However, if we draw the line the other way around, where we draw from bottom-right to top-left, then the pivot point will be at the bottom right (think of an hour clock arm between hour 10 and 11). This means that objects crossing from the top-right to bottom-left are now moving in the counterclockwise direction, and vice versa, as shown below.

Now for a more practical example, the “car count” line in the image below is drawn from top-left to bottom right. This means that the vehicle that is about to cross will be crossing in the counterclockwise direction.