How to make "Sat-nav" work inside a Tesco Store

If you have been reading in the media about my proposal to have a form of in-store "satellite navigation"-style location based awareness for Tesco Finder app users, I thought I would take you on a dive into the sort of research we're doing to see if we can make this work.

Now we don't do 'tech' for its own sake so let's examine the use cases:

1. "As the customer, I wish to be guided to the product I am looking for in the store".
2. "As the customer, I wish to be alerted by my phone whenever I am close to a product I have stored in my shopping list".
3. "As the customer, I wish to be alerted by my phone whenever I am close to products on special offer that are similar to products in my shopping list".
4. "As the customer, I want you to show me a map of the store layout, and on it show where both I am and where all the products in my shopping list are located".

Wow, we need some good data to satisfy these requests! Let's see what we have:

1. We know where all grocery products are in every UK Tesco branch as long as it is bigger than an Express-sized format. This data is already provided to Tesco Finder users.
2. We are already obtaining good aisle and shelf location spatial data from software that is used by Tesco merchandising teams that creates planograms. We haven't made this live yet but it's looking good. Tesco Finder would take this data and draw out all the aisles on the screen. We're making sure we describe the layout using as few characters of data as possible (I hope other app writers think as carefully about your data plan limit and keep the amount of data transferred down as much as all Tesco app authors do).

So we know every product that every Tesco branch stocks, and where it is laid out spatially in that branch. We know what products are on special offer and what the nature of that offer is. We just need to update the Tesco API server interface to make the spatial/map data available in as few characters as we can, and code a version of Tesco Finder to support the store map. That work is in progress, and we have found everything we need to make it work.

So "all" that is left now is to work out where the customer is, on a phone that loses the GPS signal as soon as they enter the Tesco branch. Hmmm...!

As you can imagine, all of our Tesco stores have wifi wireless network access points built into various parts of the building. These provide staff with the ability to enjoy network connectivity from their various handheld devices as they go about their tasks, so this is a critically important part of our in-store infrastructure.

Each access point has a unique identifier - a Media Access Control (MAC) address - which it supplies in every piece of signal data it transmits. We can tune into the wireless data chatter and read the MAC address without actually having to connect the phone to the access point. Indeed the phone doesn't have to transmit anything - just listen.

If we were to:

1. Tell the phone (using the API) where the access points are on the store map and what their unique MAC addresses are, and
2. Get the phone to measure the relative signal strengths of the wireless signals coming from these MAC addresses...

..then we could get the Tesco Finder app to work out where it thinks it is on the map.

Some fairly simple mathematical formulae is all that's required but given that a picture paints a thousand vector symbols, you can see how it would work in this diagram (click image for larger version):

I have colour-coded 6 access points so you can see how the phone might work out where it is in the store. Given that the lower signal strength is most likely to mean a more distant access point, and because the phone knows where all the access points are located, it can work out where it is.

Job done? Not quite... radio waves are a finicky phenomenon (I should know as I am a licensed radio amateur). From a radio point of view, Tesco sells a diabolic mix of products that reflect, refract and absorb signals. As the phone moves around, these three corrupters of signal purity will be in full force wrecking the ability of the app to work out where it is.

For example, walk down the aisle full of bottled waters and it is quite possible that nearer access points will become weaker than more distant ones as these stronger signals are absorbed more by the water. Walk down the baked bean aisle and those tins are reflecting signal like you wouldn't believe. These rarely affect the staff equipment since the system allows staff devices to roam quickly between access points. It's only us who needs to know about each particular access point. 

So now you know why this an R&D project. Tesco Finder needs to work out (probably through some sort of averaging) where it thinks it is in a way that is quick and accurate enough to be credible to the customer. If we crack this, it means that we can provide in-store "satnav" style help with zero change in the infrastructure. We're going to have a damn good go!

P.S. Once again can I point out to journalists that I am Head of R&D for Tesco.com (which just so happens to that part of Tesco pushing apps out in an R&D context). I am not Head of R&D for Tesco. Somebody else is!