Online, an impression is an ad served on a page. In store, an impression is a shopper passing within the visibility radius of a screen, end cap or display while the creative is on air. It is verified when it is counted from real shopper positions instead of being estimated from store traffic.
The difference matters because two screens in the same store can reach very different audiences depending on where they hang. Shoppermotion counts the trips that entered the area from which each placement can be seen, using the positions of tagged trolleys and baskets, so every placement gets its own audience figure.
Impressions are the first step. A view is counted when the trip stays in the visibility area below 45 cm/s for at least the minimum time set for the format, typically one to three seconds, and view rate (views divided by impressions) is the best indicator of whether a placement is noticed. A click is a viewer who then walks into the promoted bay, and click-through rate is clicks divided by views.
Opportunity to see (OTS), the share of store trips with an impression, makes inventory comparable across stores: a screen with 43% OTS in a small store may be worth more to an advertiser than one with 12% in a hypermarket. For digital signage, the same paths measure each screen's impacts, stops, visits to the advertised category and purchases of the advertised product.