GPS / GNSS — como funciona o posicionamento por satélite.

GPS (Global Positioning System) is the United States satellite constellation that began civilian operation in the 1990s — 31 satellites broadcasting timing signals from medium Earth orbit.

GNSS (Global Navigation Satellite Systems) is the umbrella term covering GPS plus Galileo (EU), GLONASS (Russia), BeiDou (China), and regional systems like QZSS (Japan) and NavIC (India).

Modern receiver chips listen to all of them at once — multi-constellation GNSS — which dramatically improves availability in urban canyons and dense foliage.

Consumer-grade GNSS accuracy is 3–5 m in clear sky-view conditions; multi-band GNSS (L1 + L5 dual-band) brings that to 1–2 m with the same antenna. For sub-metre or centimetre accuracy, see /insights/gnss-rtk-explained.

Each satellite broadcasts its precise position and the exact time.

A receiver listens to at least four satellites, measures the time each signal took to arrive (which, multiplied by the speed of light, is the distance to that satellite), and solves the geometry to compute its own 3D position and time.

The receiver doesn't transmit anything back — GNSS is a one-way broadcast.

Cold-start time (first fix from a powered-off receiver) is typically 30–90 seconds for ephemeris download; A-GPS (Assisted GPS) over cellular or Wi-Fi delivers ephemeris and almanac data in seconds, cutting cold-start to under 5 seconds.

Multi-band receivers compare L1 (1575 MHz) and L5 (1176 MHz) signals to cancel ionospheric error, the largest source of standard-GNSS inaccuracy.

Five categories are mature. Vehicle and fleet telematics: every truck, van, delivery vehicle, taxi and shared scooter on the road today carries standard GNSS — accuracy is sufficient for route auditing, geofencing, ETAs, driver behaviour and asset recovery.

Outdoor asset tracking: shipping containers, returnable assets, plant equipment, livestock — standard GNSS combined with cellular (LTE-M / NB-IoT) or LoRaWAN backhaul.

Construction and field-service equipment: yellow-iron telemetry, run-hours, theft recovery, geozone enforcement.

Mobile workforce and last-mile delivery: courier proof-of-delivery, route compliance, on-time arrival evidence. Consumer wearables and sports: GPS watches, fitness trackers, recreational cycling computers.

GNSS vs RTK-GNSS: standard GNSS gives 3–5 m; RTK gives 1–3 cm. Same satellites, different receiver and correction pipeline. RTK is required for precision agriculture, construction machine control, autonomous outdoor vehicles and survey.

GNSS vs cellular positioning: cellular triangulation gives 50–500 m and only works in coverage; GNSS is independent of any network. Many devices use both with cellular as fallback indoors.

GNSS vs Wi-Fi positioning: Wi-Fi gives 10–50 m indoors where GNSS fails. GNSS vs UWB / BLE / RFID: completely different categories — GNSS for outdoors with sky-view, the rest for indoors and dense environments.

GNSS vs hybrid GNSS-LPWAN: newer chips (Semtech LR1110 / LR2021) integrate GNSS sniffing into LoRaWAN devices for ultra-low-power outdoor tracking — GNSS for position, LoRaWAN for backhaul, weeks-to-years on a battery.

Five constraints are real. Sky-view required: GNSS fails indoors, in tunnels, under heavy tree canopy and in urban canyons ("multipath cities" — Manhattan, Hong Kong, central London). Accuracy is consumer-grade: 3–5 m typical, 1–2 m with multi-band.

Not sufficient for surveying, machine control, or precision agriculture. Power consumption: continuous-fix GNSS draws 20–50 mA — battery-powered trackers need duty-cycle scheduling, sleep modes, or hybrid GNSS-LPWAN to last weeks or years.

Spoofing and jamming: GNSS is unauthenticated and trivially spoofable by anyone with a software-defined radio; defence, critical-infrastructure and ride-hail applications increasingly need anti-spoofing measures.

Cold-start latency without A-GPS: 30–90 seconds is too slow for many use cases — A-GPS over cellular is now table-stakes for asset trackers.

Silicon and modules: u-blox dominates enterprise-grade GNSS modules — MAX-M10 (low-power multi-constellation), NEO-M9N (multi-band consumer), ZED-F9P (precision RTK).

Quectel (L76, L80, LC76G), Telit (SE150, SL871), MediaTek (MT3333, MT5933), Broadcom (BCM4775) and STMicroelectronics (Teseo) compete across price points. Application processors: Qualcomm, MediaTek and Samsung integrate GNSS into smartphone SoCs.

Cellular-GNSS combo: Quectel BG95-M3 and u-blox SARA-R510 combine LTE-M / NB-IoT cellular with multi-constellation GNSS for asset trackers. Hybrid GNSS-LPWAN: Semtech LR1110 / LR2021 integrate GNSS sniffing into LoRaWAN.

Service ecosystem: Skyhook, Combain and Google Geolocation API for cellular and Wi-Fi positioning fallback. A-GPS: SUPL servers from u-blox AssistNow, Broadcom and major MNOs.

Use cases requiring outdoor position where 3–5 m (or 1–2 m with multi-band) is sufficient: vehicle and fleet telematics;

outdoor asset and returnable-asset tracking with cellular or LoRaWAN backhaul; field-service equipment telematics; courier and last-mile delivery; construction yellow-iron monitoring.

We recommend stepping up to GNSS-RTK (/insights/gnss-rtk-explained) for autonomous outdoor vehicles, precision agriculture, construction machine control and survey-grade applications.

We recommend hybrid GNSS-LPWAN (Semtech LR1110 / LR2021) when battery-powered asset trackers need years of life with periodic outdoor position. For indoor or building-canyon environments, GNSS isn't the right tool — UWB, BLE-AoA, Wi-Fi RTLS or visual SLAM are.