I have always assumed the word “impression” was chosen intentionally for OOH measurement. What advertiser wouldn’t want to convey an idea, feeling, or opinion about something or someone, especially one formed without conscious thought? One impression seems like a pretty big deal. Multiply that by thousands and thousands and you begin to understand the power of Outdoor Advertising!

The word “Impression” is the most important next-thing for OOH & DOOH. Potentially – done right – OOH impressions can allow trading alongside digital media and compete for the largest ad budgets. It is also a potential mine-field with the chance for loss of credibility and trust.
Out of home media audience was formerly limited to traffic counts, as a basis of defining potential exposure or as a blunt indication of Opportunity To See (OTS)
Individual site attributes like size, angle and viewing length were used as a classification variables to determined the likelihood of actually being seen (LTS)
More sophisticated attribution tools such as eye-tracking and even neuroscience have allowed us to apply a Visibility Adjusted (VA) factors to OOH & DOOH assets.
We are getting really close to predicting actual audience impressions.
Device-based location data plus VA factors, offer precise audience data and this is where the best OOH measurement tools are currently; Geopath, Route, etc.
The final hurdle is the multiplier and the divider, for DOOH.
As a one to many medium we are justified to multiply one physical showing on a digital board, to represent exposure to many people at one time.
However we also have to divide the exposures result to factor in the time when your ad is not displayed, when sharing the loop with other content.
We have to tackle the share of time issue with professionalism and candour if we are to promote our media with reliable impressions data.

How do you characterize an Out of Home Impression?
Do you have a description other than the clinical one shown above?

These are excellent and relevant questions that Rick Robinson’s “The Intimacy of One-to-Many” essay eloquently brings to life in his terrific description of how we, as consumers, interact with OOH messages of all forms.
For me, I was taught early in my career – back when the DEC was the standard and only measurement – that an impression is “an opportunity to view” – which is true, but, boring and sterile.
Over the course of my career, I have come to think of an impression as so much more. To Rick’s point, when we speak about impressions in OOH there is both the clinical description AND the EMOTIONAL description. OOH is most powerful when the messaging – whether on a spectacular, oversized wallscape or a piece of street furniture – engages the consumer on that emotional level. It is at that point that the brand messaging has succeeded by creating a moment of relevance with the consumer.
I think of it this way: Impression is derived from the word “impress” which is defined as: “To make (someone) feel admiration and respect.” AND/OR “An act of making an impression or MARK.” As such, a “true” impression resonates on a level that transcends the ephemeral a deepens the relationship between the viewer and the brand. Anything less is just “an opportunity to view” which, from a brand perspective, is an opportunity lost.