Cellular Mapping Limitations

This page logs known limitations in Broadband Map's cell coverage data. Limitations in internet availability data are covered separately on the ISP Metrics & Limitations page.

Signal Strength

• Maps show estimates of outdoor signal strength. Coverage quality can be much weaker indoors and varies dramatically based on buildings' construction characteristics.
• Maps only show signal strength from the native network. Roaming coverage is not accounted for and may vary between different plans on the same native network.
• For the moment, Broadband Map primarily relies on measures of signal strength. While signal strength generally serves as a good proxy for connection quality, it doesn't account for everything that can affect users' experiences. For example, congestion levels often have a dramatic effect on the speeds experienced by network users. Congestion can be severe despite strong cell signals.

FCC Data

• Broadband Map relies primarily on data that network operators report to the FCC through the Broadband Data Collection (BDC) program. Network operators estimate coverage areas and signal strength using statistical and geospatial models. While the estimates are informative, they're imperfect.
• While parts of the FCC's coverage-modeling process are standardized, network operators' approaches still differ materially. Because the FCC uses this data to inform telecom policy and subsidy decisions, network operators may have incentives to understate or overstate coverage. Broadband Map's supplementation of BDC data with real-world data partially, and imperfectly, mitigates these issues.

Crowdsourced Data

• Much of Broadband Map's crowdsourced data comes from devices designed to collect data about vehicles. The devices' hardware and the way they're used won't perfectly match typical phone hardware or the behavior of normal consumers.
• Broadband Map's crowdsourced data from consumer handsets mixes a variety of contexts: indoor, outdoor, stationary, and in-motion. The mix of contexts represents how real consumers use their phones, but it complicates using and interpreting the data.

Granularity

• BDC data is at the level of resolution 9 H3 cells. These cells are typically about 0.11 km² (0.04 mi²). Cell signals can vary between points within a cell, especially in places with buildings and other significant obstructions.
• GPS information associated with crowdsourced data isn't perfectly accurate. While devices typically report measures of GPS precision, allowing some filtering of dubious data points, some imprecision about location remains.