How to Calculate Impressions for OOH Advertising

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Out-of-home (OOH) media has been largely blossoming over the past years.

There are various reasons behind this, including the simple fact that OOH campaigns are renowned for being easy to measure in terms of engagement, impression and ROI. 

Historically, the same could not have been said for most offline marketing channels, particularly out-of-home (OOH) media and billboards.

This is no longer the case, however, with the OOH advertising industry having developed several innovative ways of calculating impressions and measuring the effectiveness of campaigns. 

We’ll break these down below, whilst asking how you can determine whether your campaign has been successful.

Getting Started – Measuring Your Audience

OOH measurement is underpinned by the so-called ‘opportunity to contact’ (OTC) principle, which is essentially a metric that estimates how many people will walk past your advert and see its content. 

To help achieve this objective, this metric will factor in both survey data and mobility modelling, and it’s fair to surmise that accurate measurements and estimations rely on information being drawn from a number of different sources.

In the case of mobility modelling, this draws data from a detailed global travel survey, which is actually based on a representative population and helps to identify patterns pertaining to the movement of your target audience.

Historically, these surveys were almost always based on memory, but they’re becoming increasingly detail-oriented and capable of drawing information in real-time. 

More specifically, real-time consumer mobility data can now be recorded and shared in real-time, largely through mobile devices and the measurement of detailed GPS and Wi-Fi signals. 

With the increased sophistication and exponential growth of smartphone technology (mobile penetration rates are now in excess of 90% for most demographics in the UK), modern travel surveys can even incorporate accelerometers, barometres and compasses to establish the modes of transport used by target consumers and the precise outlets that they visit.

Of course, the motorists amongst you will often notice 48 or 96-sheet billboards positioned at roadsides and along busy commuter routes, with this type of advert ideal in a society where 36% of the UK population continue to drive to and from work on a daily basis.

So, another key OOH measurement tool is provided by vehicular data, which incorporates wider travel survey information with big data sets of traffic flows from targeted geographical regions.

This broad data set is extremely beneficial for OOH marketers, as it can help to collate information on every conceivable mode of traffic and simultaneously draw statistics from several different sources.

These include official government traffic counts, transport authority data and GPS signals, while the continued integration of real-time sensors on ad panels is also helping to create a deeper level of insight and deliver more accurate information.

As an extension of this technology, digital billboards are increasingly using in-built sensors and cameras to observe consumer behaviour and measure engagement in real-time.

Interestingly, this practice has come under fire in some instances, with the Dutch Data Protection Authority AP in the Netherlands introducing a regulation that compels advertisers to secure permission from passing customers to ensure compliance with current GDPR laws.

Regardless, there’s little doubt that this technology is here to stay in the UK, as advertisers look to increase the accuracy and efficacy of their OOH measurement techniques and access more detailed insights in the process.

How do I measure OOH impressions?

The number of impressions (or views) generated by outdoor ads is central to the success or failure of any campaign, and this is the single most coveted metric amongst marketers and business owners.

There are several different methods used by brands to calculate ad impressions, depending on the location of your billboards and the resources available to your firm. These include:

Travel surveys

We start with the industry standard for calculating OOH impressions, with travel surveys having being used successfully throughout the digital age.

Ipsos Connect is one of the leaders in the field, with the group having conducted travel survey fieldwork that has seen more than 50,000 respondents participate since its inception. 

These surveys use digital ‘MobiTest’ devices to track respondent’s movement, whilst garnering highly granular and sophisticated data sets that offer huge value to marketers.

This includes the real-time location of participants, their speed and direction of travel, along with their altitude and the temperature of the surrounding environment.

From an OOH advertiser perspective, selected data sets can be overlaid with a comprehensive map of outdoor advert locations, offering an insight into the traffic flows that pass individual billboards.

Incredibly, this data will also tell you how many people faced your advert and how long they stood in front of it, and this can offer a unique insight into the level of engagement that exists between a brand and its customers.

By being able to track a respondent’s movements after they’ve engaged with an outdoor advert, brands can also determine the effectiveness of their communications and additional conversion metrics.

Local Government Data and Traffic Levels

Whilst travel surveys remain the most effective and technologically advanced way of garnering data and calculating impressions, there are other methods and data sets that can be leveraged by brands (particularly those who have installed large-form roadside billboards).

One option is to access data from local government that details the traffic levels in targeted areas, which can then be cross-referenced and mapped against OOH post sites.

The Department of Transport in the UK is known to keep maps that details traffic flows and levels on Britain’s comprehensive A-road and motorway networks, for example, and brands can search any area in the UK before pulling up a series of selected “count points”.

From here, you can download specific traffic data that pertain to your ad sites, affording you an insight into how many impressions you’re likely to have achieved in each location.

You can also seek out further data relating to traffic flows and the speed of vehicles as they pass, helping you to understand potential engagement levels and how much exposure your message has benefitted from in a host of different locations.

3D maps and visibility adjustment indices

Some brands may also use three-dimensional digital maps of outdoor space and interior locations such as tube and train stations (which remain popular outlets for smaller billboards and OOH messaging).

These accurate maps are also used to replicate the type of 3D interiors found in shopping centres, making it possible to measure the flow of traffic and views in OOH environments that have been historically hard to measure.

These maps can also be combined with so-called ‘Visibility Adjustment Indices (VAIs), which essentially factor in the physical characteristics of an outdoor structure or ad location to provide more accurate impression calculations.

These include everything from the precise placement of the unit to the distance at which an ad is typically viewed and its size, and this detail-oriented approach creates a far greater level of insight whilst identifying any potential issues that may impact on engagement.

This is an important consideration, as whilst these methods of measuring impressions are becoming increasingly effective it remains hard to determine how many people have actually absorbed a message.

To compensate for this, some of the more advanced OOH measurement systems incorporate algorithms that have been built on in-depth eye-movement research and accepted psychological theories.

By leveraging these principles in conjunction with travel surveys and local government data, it’s far easier to gauge and analyse audience behaviour in the most effective manner.

These measurement systems can also be used to convert viewable impressions (OTCs) into actual viewed impressions (VACs), providing the final frontier for brands in the field of cost-effective outdoor advertising.

Alternative methods of measuring OOH campaign effectiveness

At this stage, you should have a broad understanding of the key metrics that can be used to measure the reach and effectiveness of your OOH campaign.

But what does all of this mean in practical terms?

Below, we’ve looked at some corporeal examples and steps that you can take to actively measure your OOH campaigns. These include:

Creating a dedicated landing page or microsite

In addition to creating a dedicated slogan for your OOH ad campaign, you should consider directing online traffic to a microsite that’s specific to your advert and messaging.

This works particularly well if you’re launching a new product and wish to advertise this exclusively through your OOH campaign, while best practice should also encourage you to display the microsite’s URL clearly on the billboard or poster.

From here, you can leverage Google Analytics to measure the number of people who visited the microsite directly online, with this capable of providing an incredibly accurate gauge regarding the effectiveness and reach of your message.

When using this marketing technique, you should also link the microsite to your main website and sales portal, as this creates an opportunity for cross-selling without compromising on your ability to measure the campaign.

Track your promo codes

Let’s say that you want to sell a brand new product at a discounted rate, with this promotion available solely through your OOH campaign and for a limited period of time.

In simple terms, you need to create a unique promo code for your OOH campaign or an individual billboard, ensuring that this cannot be accessed through any other channel.

Ideally, customers should be directed to your site and purchase the promoted product using the dedicated promo code, with this providing a quick and simple way of determining how many sales were driven by your campaign.

The execution of this technique is also important, especially in terms of how you articulate the offer. 

Most importantly, you’ll need to use concise messaging and minimise the amount of text used on your billboard, while promoting the extent of the discount and the requisite promo code. 

Consider the merits of social media and hashtags

We’ve already touched on the growing link between OOH and social media marketing, with the former increasingly likely to drive activations through sites such as Twitter and Instagram in particular.

With this in mind, one of the best ways of measuring billboard or OOH effectiveness is to create a unique hashtag to engage potential customers offline.

Make no mistake, hashtags have become increasingly prominent in the field of social media marketing, while there are also numerous tools that help you to understand which hashtags are most likely to resonate with your audience.

By heavily promoting your hashtag through your ad, you’ll have an accurate and insightful way of measuring any social media engagement that follows the publication of your ad.

Social media channels also enable you to understand more about the individuals who are searching for your brand online, and this can deliver far greater insights going forward.

The Last Word

As we can see, it has never been easier to measure the effectiveness of your OOH campaigns, with innovation and the emergence of integrated marketing campaigns helping this drive enormously.

It’s also important to remember that whilst calculating ad impressions is central to any successful OOH advertising campaigns, you must apply the same level of analysis and insight across every single stage of the customer journey.

In fact, there are numerous ways through which you can measure both the impressions generated by an OOH ad and its subsequent impact on sales, so the key is to select those that are most relevant to your budget, content and core marketing objectives.

Remember, execution is also key here, so be sure to keep your messaging concise and to the point when designing billboard ads!

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