Interactive publication
Back to the catalogueMeasurementCase 04 of 05
Shared-vendor crosswalk correlation
Most platforms resolve IP to location through the same few vendors, so location reports from different platforms are correlated, not independent: cross-platform agreement is not corroboration, and every party can be wrong in the same direction at once. Requested-vs-executed provenance verifies the platform's own conversion step and passes the shared upstream lookup error through untouched.
Class
Case to account for
Affects
1 conversion
01
Detection
Ask each reporting platform which geolocation vendor and database vintage produced its location field; matching vendors means correlated errors.
02
Mitigation
01
Never treat multi-platform geographic agreement as independent confirmation when platforms share a lookup vendor
02
Scope provenance claims explicitly: conversion verified, upstream lookup not
03
Calibrate against a location signal that does not pass through the shared vendor (GPS-declared impressions, physical delivery points)
03
Affected conversions
IP lookupH3 (probabilistic crosswalk)
OPEN