GNSS reflectometry · lakes · reservoirs · rivers
BREVA reflexa measures water level from the satellite signals the surface reflects. A solar unit, an hour to install, nothing in the water, and the level delivered by satellite from anywhere on Earth.
Test session on a lake: the unit on the wall measured 2.276 m to the water and reported it over Iridium in 40 bytes.
No pressure tube, no float, no radar over the stream. Nothing for floods or debris to destroy.
Fix it to a wall, a pole or a bridge, aim it at the water on a map, verify it live, leave.
Iridium reports from places with no mobile network and no mains power.
Computed on board from every satellite pass, with a quality check on each one.
Who needs it
Dam and reservoir operator
A reservoir level every session from a unit on the crest or the shore, independent of the existing gauge, with no part in the water and no cables to the lake.
Then: watch how the dam itself responds to the level with GeoGuard units, which add continuous millimetre displacement monitoring.
Regional flood monitoring
Many low-cost gauges along a basin, installed in an hour on a bridge or a bank, powered by a small panel and reporting over satellite where there is no mobile coverage. A survey run tells you on day one whether a site works.
Then: GeoGuard units at the critical points, monitored continuously for warnings in real time.
Networks and research
Weather and hydrological station networks add a dedicated water-level gauge next to their stations. A reflexa unit does one job, reflectometry, and reports a few bytes per session; arcs and diagnostics download over USB.
Then: full BREVA processing of the data for long, validated water-level series.
How it works · GNSS interferometric reflectometry
The signal
A GNSS antenna near water hears every satellite twice. The reflected copy travels an extra distance that grows with the antenna height and the satellite elevation.
The measurement
Seen against sin(elevation), the signal strength oscillates at a constant rate. A Lomb–Scargle periodogram finds it; the wavelength λ of the L1 signal turns it into metres.
The footprint
Low satellites reflect far away, high ones close by. For a 3 m antenna, reflections at 5° come from about 50 m out, so waves average out and nothing touches the water.
The field console
Normal mode guides an installation in five pages. Advanced mode exposes every setting and diagnostic. macOS, Windows and Linux.
Field results
A 32-minute session on Lake Lugano. The unit computed the water distance on board and sent a 40-byte report over Iridium.
Iridium report · format C3 · 40 B
c3 74 18 5e 18 46 d0 35 d6 03 62 01 1c 8d c0 e8 2e 20 b3 e0 f0 15 40 a9 10 e0 01 fc a4 40 da 07 ea d0 d2 17 c0 d0 9b 10
Technical datasheet
Downloads
Manual
The full manual lives in the documentation. The same pages open from the "?" button inside the app.
Chapter 1
Before you start: a charged unit, a data-capable USB-C cable, the field console, and a tape measure for the antenna height.
Chapter 2
The Station page shows the map, your sectors and where the reflections land.
Chapter 3
Choose how often and how long to record, and when to send.
Chapter 4
Live shows the satellites, the arcs and the first water distances while you are still there.
Chapter 5
Every session and arc the unit reported, with exports.
Chapter 6
A compact report of about 22 bytes after each session, anywhere on Earth.
Chapter 7
Keep the unit healthy and up to date.
From one unit to continuous monitoring
A reflexa unit does one thing, water level by reflectometry, where a small self-powered gauge is enough: it measures in sessions and reports a few bytes a day. Where water and structures must be watched continuously, GReD runs reflectometry as a service together with GeoGuard GNSS displacement monitoring, on larger units built for harsh environments that support up to two antennas each.
| reflexa unit | GeoGuard + GReD reflectometry | |
|---|---|---|
| Best for | Remote lakes, rivers, surveys; places without power or network | Dams, reservoirs, bridges, coastal and critical infrastructure |
| Measurement | Sessions; a summary per session | Continuous, every satellite pass, multi-receiver |
| Hardware | Compact single-antenna unit, solar | Larger units for harsh environments, up to 2 antennas per unit |
| Data link | Iridium, a few bytes per day | Continuous upload, full raw data |
| Processing | On the unit | BREVA processing chain, validated time series |
| Measures | Water level only (reflectometry) | Millimetre 3D displacement, water level by reflectometry, other integrated sensors, correlations, alerts, dashboard and API |
Start with a reflexa unit, scale to continuous monitoring on the same site and the same signals. More on continuous monitoring at geoguard.eu.
Open the 3D viewinfo@gred.eu
