How GPS-Verified Ad Delivery Works

How GPS works on a consumer phone

Every modern smartphone runs a multi-constellation GNSS receiver (GPS, GLONASS, Galileo, BeiDou) paired with a sensor fusion stack: accelerometer, gyroscope, magnetometer, barometer. The receiver locks onto satellite signals, computes pseudoranges, and resolves a 3-D position fix.

On its own, raw satellite acquisition is slow. A cold start takes minutes to first fix. Smartphones short-circuit this with Assisted GPS (A-GPS): the cellular network downloads ephemeris and almanac data to the phone over the radio link, so the receiver knows where to look in the sky and locks in seconds rather than minutes.

A-GPS plus Wi-Fi BSSID lookup is what gets a phone to its quoted accuracy floor. The figure to anchor on comes from the people who run the constellation: GPS.gov states that GPS-enabled smartphones are typically accurate to within a 4.9 metre radius under open sky, and that accuracy worsens near buildings, bridges and trees. That last clause is the one that matters for advertising geometry, and the limitations section below takes it seriously.

Smartphone under open sky

4.9 m

GPS.gov: smartphones are 'typically accurate to within a 4.9 m (16 ft.) radius under open sky'

GPS.gov (US government), GPS Accuracy

Government commitment on the signal itself

2.0 m

Daily global average user range error, the error budget before any receiver or environment effect

GPS.gov (US government), GPS Accuracy

Urban canyon (peer-reviewed)

7-13 m

Measured iPhone horizontal accuracy in a dense city grid

Smartphone GPS accuracy in urban environment, PLOS One

WilDi's own app vs. bid-stream-inferred location

There are two ways an ad platform can know where a phone is. They produce wildly different accuracy and economics.

Bid-stream-inferred location. The ad platform never touches the device. It listens to OpenRTB bid requests flowing through ad exchanges. Each request may carry a coarse lat/lon attached by the publisher's SDK, plus a mobile advertising ID. The platform decides whether the device is “near” a billboard or geofence and bids accordingly. The whole auction has to clear before the page or app finishes loading, which leaves the bidder a fraction of a second to decide, so the location call is necessarily a fast inference rather than a measurement.

WilDi's own app. Members install WilDi Maps on their own phones and opt in to location sharing. As they move around the cities WilDi serves, the app reports the phone's GPS position directly to WilDi's delivery system: no exchange, no bidder, no SDK rake. When a member enters a road or area a business chose, WilDi's server selects a matching active message and sends it to that member's phone. The location signal comes straight from WilDi's app instead of being purchased downstream of three intermediaries.

The verification step: from GPS fix to billable acknowledgment

“Verified” is a load-bearing word in the model. It covers four separate steps, listed below: location qualification, sending the message, the member's acknowledgment, and billing. A delivery record is only written when the phone's reported GPS position falls inside the road or area the business chose when the message is sent.

Stated in full: a WilDi verified delivery is not an estimated impression. It is a qualifying acknowledgment: an auditable app event in which an opted-in member receives the business's message at the required location, acknowledges it by tapping the WilDi button, and the acknowledgment passes WilDi's billing rules. That definition is deliberately narrow. Most advertising currencies charge for modeled exposure, qualified impressions, or inferred attention, and several of them measure well: Geopath adjusts circulation by a Visibility Adjustment Index built from eye-tracking research, the UK's Route publishes a Likelihood to See figure, Place Exchange PerView establishes device presence deterministically, GroundTruth ties exposure to a later visit, and Quividi reads head direction on camera-equipped screens. Out-of-home has had an accreditation-grade standard since the MRC finalized its Out-of-Home Measurement Standards on December 4, 2025. What separates this model is the unit, an explicit acknowledgment by the recipient, and an acknowledgment proves an intentional human interaction rather than cognitive attention.

1. The phone reports its position while the member drives. With the member's permission, the WilDi app reads the phone's own location service (Core Location on iOS, FusedLocationProvider on Android) at a configured cadence. The fix is A-GPS-assisted with Wi-Fi BSSID and inertial sensor fusion.
2. Location qualification. The server runs a point-in-polygon test against the geometry of each active road or area. If the point is inside, the phone is eligible for that business's message.
3. Message selection. WilDi's server picks an active message for that road or area. There is no auction: the rate is fixed by the business's deposit tier. A zone hexagon is held by one business at a time; more than one business can run a tunnel on the same road.
4. Send and record. The message appears in the WilDi app on the member's phone. The server writes a delivery record stamped with the device ID, the GPS fix that qualified it, the road or area ID, and the timestamp. A delivered message on its own is not billed.
5. Acknowledge, then bill. If the member taps the WilDi button and the acknowledgment passes the billing rules, it is a verified delivery and the rate is debited from the business's prepaid balance. No acknowledgment, no charge; no qualifying location, no charge. Opening the business's website, calling it, or getting directions are separate actions; none of them is the acknowledgment.

Privacy and data handling

The privacy posture is structurally different from consumer SDK location collection because the location comes from WilDi's own app, which the member chose to install. The member opts in to location sharing when joining, and the GPS stream is used to run WilDi's delivery service, not sold downstream to data brokers.

On the advertiser side, the only signals leaving WilDi infrastructure are aggregate delivery counts and (if the advertiser opts in) attribution joins via the lead-capture pipeline. Individual member coordinates do not leave WilDi's systems, are not joined to consumer identifiers, and are not exposed in the OpenRTB ecosystem.

On the member side: members chose to receive messages in WilDi's app and earn a share of the advertising spend for qualifying acknowledgments; they are not followed across other apps or sites. The model does not require Apple App Tracking Transparency consent for cross-app tracking, because there is no cross-app tracking. The message is shown inside WilDi's own app. iOS ATT governs IDFA access for cross-property advertising; that question doesn't arise here.

For OS-level context, see Apple's App Tracking Transparency documentation and Android's location permissions developer guide. Both frameworks distinguish between an app using location for its own service (what WilDi does) and cross-property tracking for advertising (what bid-stream targeting does).

Limitations: urban canyon, indoors, edge cases

The model inherits the same physics every other GPS system inherits. Pretending otherwise would be dishonest.

• Urban canyon multipath. In dense downtown grids, satellite signals reflect off glass towers before reaching the phone. GPS.gov says as much in one line, that accuracy worsens near buildings, bridges and trees, and peer-reviewed iPhone measurements published in PLOS One put the horizontal error at 7 to 13 metres in a dense city grid, against 4.9 metres under open sky. WilDi roads and areas are drawn to allow for that: a tunnel isn't a 5-metre line, it's a street-aligned polygon.
• Indoor delivery. GPS effectively does not work indoors. People parked in covered garages, tunnels, or warehouse loading docks will not produce location fixes inside a road or area during those windows. The model does not pretend to deliver impressions to phones whose GPS is dead.
• Cold start. First fix after a phone reboot or extended power-off can take seconds; A-GPS shortens this dramatically but does not eliminate it. Deliveries during the cold-start window are not counted.
• Spoofing. A bad actor running a mock-location app could try to fake being inside a road or area. WilDi uses the phone's own motion and GPS to check for a real trip, and flagged activity is never billed.
• Coverage geography. A road or area only delivers when a participating member is inside it. Off-peak hours and low-density areas deliver less. Pricing is per verified delivery, not per hour, so the business is never paying for empty roads.

The CPVD pricing model

Cost Per Verified Delivery (CPVD) prices the verified delivery defined above. A message shown on one member's phone, with a server-checked GPS fix inside the road or area the business chose, is not billed on its own; it becomes a verified, billable delivery only when the member taps the WilDi button and the acknowledgment passes the billing rules. The rate is set by the account's monthly deposit tier rather than by an auction: $0.25 per verified background delivery at Enterprise ($3,000 a month and up), $0.32 at Pro ($1,000 and up), $0.40 at Local ($250 and up), $0.50 at Starter below that. Tunnels and zones cost more than background, so 'from $0.25' is a floor, not a flat price.

There is no CPM. There is no bid. There is no exchange fee, SSP fee, DSP fee, ad-server fee, or verification-vendor fee. The advertiser is billed the tier rate for the delivery and nothing is skimmed on the way, because there is no middleman stack between them.

For the full pillar treatment of how this compares to standard programmatic OOH, see Cost Per Verified Delivery. For why the model matters financially, see What is the Middleman Tax?