Introduction: A barometer gives a long range FPV pilot a pressure-based height reference, and understanding that input explains why altitude hold feels locked in one day and wanders the next.
Long range flying pushes a quad far enough that the pilot spends most of the flight managing height by eye through a video feed, and small throttle mistakes add up over a ten or fifteen minute cruise. Altitude hold takes some of that load off, but it behaves differently from the way many pilots expect: it is not a hard floor or a fixed number the drone snaps to. It is a pressure reading, turned into an estimate, turned into small throttle corrections. Once that chain is clear, the odd windy-day behaviour makes sense, and the choice of a board with a real barometer on it becomes easier to judge.
What the DPS368 barometer measures before altitude hold begins
The DPS368 is a small digital pressure sensor on the flight controller board. It measures the ambient air pressure around the frame and passes a digital value to the flight controller, and it tracks temperature alongside pressure so the reading can be compensated as the board warms up during a flight. Axisflying lists a DPS368 barometer on the H743 PRO, a board aimed at 5–10 inch builds with 30.5×30.5mm M3 mounting and seven UART ports for peripherals. That sensor is the start of the whole chain: no pressure change, no altitude estimate, no correction. Air pressure falls as a drone climbs, but the change per metre near sea level is tiny, so the sensor has to resolve very small differences to be useful at the 20–100 m heights that matter on a long range cruise. Where the sensor sits also matters. It lives inside a frame, on a board, under a canopy, close to spinning props, so the pressure it samples is not quite the free-air pressure at the drone's altitude. Prop wash, canopy openings and frame turbulence create small pressure pulses that arrive as altitude noise.
How pressure data becomes an altitude estimate for the flight controller
Turning one pressure sample into a throttle correction is a short chain, but each step shapes how the quad feels in the air. A pilot expecting the machine to lock onto a number the way a GPS coordinate locks will be surprised, because the flight controller keeps rebuilding a moving estimate and nudging the machine toward it.
- Pressure sampling and temperature compensation: the sensor reads ambient pressure continuously and pairs each value with a temperature measurement, converting raw counts into a pressure figure the controller can use. Errors at this stage rarely show up as a jump; they creep in as slow drift across a long flight as the board and the outside air change temperature.
- Filtering and smoothing: raw pressure data is noisy, especially with props churning air around the frame, so the controller averages and filters the stream before trusting it. Heavy filtering gives a calm, slow response that lags behind real climbs; light filtering reacts fast but twitches with every gust and every throttle punch.
- Correction against a target: the filtered estimate is compared with the height the pilot has asked the controller to hold, and the difference becomes a small collective adjustment. How hard that correction pushes is set by tuning. Too aggressive and the quad hunts up and down; too soft and it sags below the target under load.
Because this is a loop, the result is always a compromise between calm and responsive, and the pilot feels that compromise directly through the throttle stick and the video feed. On a steady two kilometre cruise leg, the quiet, boring behaviour of altitude hold is the filtering and gain work happening invisibly in the background.
Where barometer altitude hold helps and where it reaches its limits in long range FPV
The benefit shows up most on the dull parts of a long flight. Holding a safe cruise height while the pilot checks a map, adjusts a camera, or lines up a return leg removes a constant low-level task from the goggles. A steady filming pass at a fixed height over ground that keeps changing is easier when the controller is managing small throttle corrections. GPS tells the pilot where the quad is; the barometer tells it how high it is relative to where the flight started, and it updates fast enough to feel connected to the aircraft rather than lagging behind it. The limits are environmental as much as electronic. Weather systems move pressure around, so the reference the controller started with can shift during a long flight, and the quad may climb or sink slightly while still believing it is holding. Wind and fast forward flight change the pressure at the sensor, which reads as height change. Terrain is invisible to a barometer: holding altitude over a rising hillside means the quad gets closer to the ground even though the number stays constant. And a badly tuned altitude loop turns a mild pressure wobble into visible porpoising. A useful way to read this in practice is to compare two flights in the same week. On a calm morning with stable air, altitude hold looks impressively solid, and a pilot can leave it running for long stretches. On a gusty afternoon ahead of a weather change, the same quad on the same tune will ride up and down, and the pilot should expect to keep a thumb near the throttle. Neither flight is a fault; they are the same sensor working through different air.
Conclusion
The DPS368 contributes one thing to a long range build: a fast, local pressure reading that the flight controller turns into a height estimate and then into small throttle corrections. Knowing the chain from pressure to estimate to correction explains both the calm cruise and the wandering afternoon. A barometer makes a good height reference for long range work, and it is one input among several rather than a replacement for position data. Pilots who expect it to behave like a fixed altitude setting will keep being surprised; pilots who treat it as a pressure-fed assistant will get the most out of it. Anyone weighing boards can look at the listed specifications of the Axisflying H743 PRO to see where this sensor sits in a 5–10 inch long range build.
FAQ
Q: What does a DPS368 barometer contribute to altitude hold in FPV?
A: It supplies the pressure measurement that the flight controller converts into a height estimate. Without it, the controller has no independent sense of climb or descent and altitude hold cannot function. With it, the controller can compare the current estimate against the target height and apply small collective corrections, which is what keeps a long cruise leg steady.
Q: Can a barometer replace GPS for return-to-home on long range FPV drones?
A: No. A barometer measures pressure and derives height; it has no idea where the drone is over the ground, which way it is pointing, or where home is. Return-to-home needs position information from GPS, and the barometer supports that job by giving the controller a height reference while the navigation side handles direction and distance.
Q: Why does altitude hold drift in changing weather or air pressure?
A: The controller holds height relative to the pressure it recorded, not against a fixed global standard. When a weather system or a temperature change shifts ambient pressure during a flight, the same physical height produces a different reading, so the quad slowly climbs or sinks to keep the number it expects. Wind and prop wash add fast pressure noise on top of that slow shift.
Sources / References
Remote Identification of Drones - Federal Aviation Administration
Open Category Low Risk Civil Drones - EASA
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