What makes it unique
| BREVA reflexa micro | Typical GNSS-IR station | Radar / pressure gauge | |
|---|---|---|---|
| Hardware | Low-cost board with an integrated patch antenna; solar + LiFePO4 | Geodetic receiver and antenna, mains or large solar | Dedicated sensor, often in or over the water |
| Processing | On the unit: results, not raw data | Raw data uploaded, processed on a server | On the sensor |
| Telemetry | ~22-byte Iridium message per session, global coverage | Mobile/Internet link, megabytes per day | Mobile link or logger |
| Contact with water | None | None | Pressure: in the water; radar: over the water |
| Footprint | Tens of metres of water surface (averages waves) | Same | A point |
| Set-up | Field console: map, terrain, live verification on site | Expert configuration | Survey and mounting |
The unit is a reflectometry gauge cheap enough for dense networks, that processes on the board and needs only a few bytes per day of satellite airtime: hardware by TU Delft and TAHMO, developed with GReD in the TEMBO Africa project (see Hardware). reflexa micro is GReD’s software for it: on-board processing with a quality check on every arc and a self-correcting search range, a field console that plans the site on a map with terrain and verifies it live before you leave, compact versioned Iridium reports, and a path to continuous, redundant monitoring with reflexa on GeoGuard.
A flexible measurement window
Section titled “A flexible measurement window”The same TAHMO WLM board can also run TAHMO’s own firmware. reflexa micro sets where and how the unit measures with wider, more flexible limits:
| reflexa micro | TAHMO WLM firmware | |
|---|---|---|
| Azimuth | 1 to 8 separate sectors, each with its own start and end, drawn toward the water on a map | One window, between a minimum and a maximum azimuth |
| Elevation | Any minimum below the maximum, up to 90°; 5°–45° recommended with this antenna; the Station page can suggest it from the mapped water | One window, between a minimum and a maximum elevation |
| Water-distance search | Auto (around the antenna-height estimate, or the widest range the elevation window resolves), widened by the unit when reflections land on its edge; or set by hand within 0.05–50 m | Reports heights in 0–20 m |
| Antenna height | Optional estimate, 0.05–250 m, or left empty: the unit measures it | — |
Several sectors follow an irregular shoreline, skip a jetty or a building, and use every stretch of open water around the unit (site requirements).
reflexa micro and continuous monitoring
Section titled “reflexa micro and continuous monitoring”A reflexa micro unit measures water level only, by reflectometry. It works in sessions and reports a summary; it is not a real-time alarm and it does not measure displacement. Where water and structures must be watched continuously, GReD runs reflexa, its reflectometry service, together with GeoGuard GNSS displacement monitoring, on larger units built for harsh environments that support up to two antennas each and carry other integrated sensors.
On a monitored site, every GeoGuard antenna that sees the water also measures its level. A dam with several stations on the crest or the shore gets several independent level series, each from its own point of view and its own stretch of water, with no extra hardware: they cross-check each other, a station that drifts or is obstructed stands out, and the level keeps coming when one station is down. Level and displacement come from the same receivers, in the same reference frame and on the same timeline.
| reflexa micro unit | reflexa on GeoGuard | |
|---|---|---|
| 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 |
| Redundancy | One point of view per unit; add units for more | Every station that sees the water measures it: several independent, cross-checked level series |
| 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 micro unit, scale to continuous monitoring on the same site. The home page shows a year of reservoir level and dam displacement from a monitored dam (anonymised), and an interactive 3D view.