--- title: "Health, explained | Nexus Observatory" description: "Interactive explainer: health and environmental exposure in 3D, chapter by chapter: low-cost sensors earn trust by co-location…" url: https://observatory.global/industries/health/explainer/ publisher: Nexus Observatory Inc. updated: 2026-11-02 --- Intro 00 01 02 03 04 05 Cities. Reference analyser; Low-cost node; Counter · aggregates only; Edge · city record Sector explainer · Cities # The street, measured block by block. Air quality, noise, traffic, urban heat and street flooding, with open data as a procurement credential. **Scenarios**: 4 **Sensing layers**: 4 **Templates**: 4 **Open projects**: 6 **01** Hybrid air quality **02** Heat and flood poles **03** Counts, not people **04** Radio layer **05** What buyers ask **01** · Air quality Co-location ## Low-cost sensors earn trust by co-location. Reference analysers plus calibrated low-cost nodes; low-cost sensors alone do not meet regulatory requirements. The method is a co-location: a low-cost node sits beside a reference analyser for weeks, a correction is fitted, and the corrected node is checked on days it has not seen. The correction here is a least-squares fit, reference = a + b·raw + c·max(0, RH − 70)², which also removes the humidity swelling optical counters read as particles. Trained on the opening days; tested on the 14 days that follow. **Error before correction**: — **Error after correction**: — **Variance explained (R²)**: — **Fitted gain and offset**: — Errors are root-mean-square, in µg/m³, on the held-out days. A corrected node densifies the network; the reference analyser still carries compliance. **02** · Heat and street flooding Microclimate ## Heat plans need a node every few blocks. Depth sensors combined with temperature, humidity and radiation nodes on poles for heat-action plans. Spacing sets the node count, n = ⌈A ÷ s²⌉, and the count sets the maintenance load: every node is a battery, a calibration and a bracket to inspect. **Nodes**: — **Nodes per km²**: — **Site visits a year, two per node**: — **03** · Noise, traffic and mobility Privacy by design ## Count the street. Never the person. Sound-level nodes, radar or video counters and probe sensing over low-power radio or 5G; privacy assessment required. The design rule: counters keep counts, never images or identifiers, and small counts are suppressed at the edge before anything is published. **Bins suppressed**: — **Share of all passages still published**: — One counter, one day, 15-minute bins with a morning and an evening peak. The threshold is set by the city's privacy impact assessment; the edge applies it. **04** · City-wide radio layer Radio planning ## One radio layer, shared by every sensor. A city-wide connectivity layer as digital public infrastructure. Low-power wide-area gateways on rooftops, or private 5G small cells where bandwidth matters: either way the count follows from the planned cell radius: hexagonal cells of (3√3 ÷ 2)·r², so n = ⌈A ÷ 2.6 r²⌉. Dense-urban LoRaWAN is usually planned at 1 to 3 km; mid-band small cells at a few hundred metres. Radio **Sites on a hexagonal grid**: — **Area per site**: — **05** · Proof Evidence ## What a city asks to see. Cities buy open, accountable data. Each item below is produced by the grid as a record while it runs. - **01** Co-location calibration reports against reference monitors - **02** Data-completeness service levels - **03** An open-data API - **04** A privacy impact assessment for video and probe sensing - **05** Accessible dashboards air quality sensor network low-cost sensor calibration hyperlocal air quality urban heat island sensors flood sensors smart city LoRaWAN open data portal integration Open work in the field: Sensor.Community, OpenAQ, FloodNet, Smart Citizen Kit, Telraam, openSenseMap. [Plan with us](https://observatory.global/contact/) [Sector overview](https://observatory.global/sectors/cities/) **06** · More sectors ## Every sector, one grid. [Sector explainer **Government and public safety** Warning starts with a measurement.](https://observatory.global/industries/public-safety/explainer/) [Sector explainer **Communities and rural** Locally owned connectivity and sensing.](https://observatory.global/industries/communities/explainer/) [Sector explainer **Industrial** Sites, ground and air on one record.](https://observatory.global/industries/infrastructure/explainer/) [Sector explainer **Sector overview** Scenarios, proof and the lines that serve it.](https://observatory.global/sectors/cities/) [Nexus Observatory](https://observatory.global/)**Health and environmental exposure** . 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