The introductory article explains the concept of trajectories and operators. Now it’s time to see how you can actually work with them. FLOW comes with a complete client application FLOW Insights that make managing your analytics and getting your results easy.

You can easily download a demo kit that contains a sandbox environment for FLOW Insights so you can try everything described in this article yourself.

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After launching the application, you’ll be greeted by the welcome screen. Select "DEMO: simulated live stream" for a quick start. 

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Below you can see what a camera view’s interface looks like. Note that the simulated camera feed may take up to a minute to initialize. We’ll start by describing the elements of the interface.

The left panel lets you switch what you can see in the rest of the UI. This article focuses on the View part. 

The View interface comprises three main parts: Video view, Programming Elements Menu, and Canvas. 

The video view on the left shows images from the currently viewed camera or recording. The simulated live stream is actually a video file on a looped playback together with trajectory data. The video view enables you to create spatial filters: zones, gates, and movements. They filter trajectories passing through a certain place. In the picture below the buttons used for creating them are highlighted.

There are also elements for zooming in and out (which can also be done with your mouse wheel) and switching to the full-screen view.

The rolling menus in the lower-left corner let you choose what you want to see in the video view: 

The Programming elements menu in the middle offers you motion filters, property filters, and set operations. You can drag any operator onto the grey canvas on the right. The picture below illustrates this process with a Speed filter.

The number under the operator shows how many trajectories are currently passed further by it. Representation of spatial filters can also be dropped onto the canvas. Let's create a Zone filter in the middle of the intersection and drop it there. 

1. Select Create zones/gates

2. Draw a freehand shape on the road

3. When you’re done, the shape will automatically be closed. Select the Create zones/gates button again to exit the creation mode. Then select the zone.

4. And finally, drag it onto the canvas.

The canvas on the right lets you freely rearrange and connect pipelines of operators (called analytics). The operators’ input connector is on the top of its box and its output is on the bottom. 

You can double-click any operator to open a dialog window that lets you change its name and other parameters specific to it. E.g. the Speed Filter lets you set conditions regarding objects' speed—the interval in which the object's speed value needs to fall into and whether the value in question is the object's maximum speed up to the current moment, minimum speed, average or current.

Let's set the Zone Filter to select only trajectories that are currently present within it, and the Speed Filter to select trajectories whose current speed is more than 50 km/h.

And that's it! Creating a system that monitors speed limits is that easy!

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