How Altimeters are Taking to the Sky—Satellites, Aircrafts, and Even SkydivingDecember 03, 2020 by Tyler Charboneau
One rewarding aspect of engineering is seeing where designs end up in applications. Electronic altimeters are such devices that have found their way into a number of interesting airborne use cases.
In a recent article, we discussed how altimeter technology—pressure, radar, and optical—has developed drastically in the past century, especially as piezoelectric ICs and LiDAR technology has taken off.
Diagram of a piezoresistive IC-based barometric altimeter. Image used courtesy of Halit Eren
One of the best illustrations of these advancements can be found in common altimeter use cases today. This follow-up article will assess how the altimeters engineers design are critical components in safe flights, skydiving, aerospace systems, and other aerial devices.
How are Altimeters Commonly Used?
Altimeters have a critical role in devices operating at extreme altitudes. Some of these include:
- Flight (personal, commercial, and military)
- Spaceflight and satellite positioning
As you’d imagine, knowing one’s location in the air while plummeting toward earth is quite important. Altimeters are critical for determining when to deploy chutes and land safely. Unfortunately, these setups don’t always excel at making information clear to users.
SmartAlti, a body-worn altimeter that incorporates ublox's Global Navigation Satellite System (GNSS) chip, works alongside a new digitized altimeter design to provide clearer altimetry with greater detail. Readouts are more accurate and indicative of what pilots might see within their cockpits.
Sample of ublox's GNSS chips, some of which were used in SmartAlti's "smart altimeter." Image used courtesy of ublox
Dekunu Technologies’ product receives updates like any software-driven device. It leverages Wi-Fi to send freefall data to cloud services. Bluetooth is also essential in creating a group dive "mesh" to share positioning data. A USB port allows for charging and diagnostics.
Space and Satellites
NASA’s Sentinel-6 satellite uses GNSS-POD (precise orbit determination) and radar pulses to determine its altitude above the Earth. This occurs particularly with respect to our planet’s oceans.
By measuring frequency pulses and their behaviors, travelers can ascertain their cosmic positioning. Even small variations in oceanic sea levels can arm astronauts (and controllers) with altimetric data. This altimeter setup makes ocean surveillance easier. Altimetry can help measure the ongoing impacts of climate change on Earth’s oceans.
Similarly, laser altimeters aboard the TOPEX/Poseidon satellite are used to create topographical maps at land and sea. Despite being beamed from space, these signals are incredibly accurate. The TOPEX altimeter can measure accurately to within two centimeters.
Many aircraft and spacecraft use laser altimeters, which beam a laser or radio signal to the ground and measure the time it takes for the signal to return, thus determining the altitude. Image used courtesy of NASA/JPL and National Geographic
Sometimes, interstellar objects are of particular interest to researchers. Asteroids travel great distances throughout space and are thus potential treasure troves for both surveyors and sample collectors. NASA and the Canadian Space Agency launched the OSIRIS-REx mission in 2018. The spacecraft is equipped with the OSIRIS-REx Laser Altimeter—which has played a key role in examining the asteroid Bennu from afar.
In fact, it constructed a 3D mapping of the asteroid based on laser imagery. The Canadian Space Agency’s altimetric technology could help us ascertain Bennu’s surface characteristics.
Safety is critical on all flights and one of the metrics pilots rely on is altitude data from altimeters. Aside from crash avoidance, altimetry can aid pilots when an emergency landing is inevitable. All collected information is crucial for flight planning and routing. Pilots can inspect the geography around them. They may also ascertain whether certain obstacles might be problematic while airborne. Instrument landing systems (ILS) also rely on altimeters to work properly.
When combined with ground proximity warning systems (GPWS) and terrain awareness warning systems (TAWS), altimeters help pilots avoid costly mistakes. Programming certain decision heights—thresholds where the plane performs an action based on altitude—at different intervals can help pilots land or abort.
Diagram of a typical altimeter used in an aircraft. Image used courtesy of Boldmethod
Militarily, altimeters integrate with a fighter pilot’s electronic flight display. An air-data computer collects altimetry information and visually displays it before the pilot’s eyes. These systems forego the popular tubular pressure design. Reducing moving parts cuts down on complexity and errors. Operators must adjust these setups for non-standard pressures, which is common when traversing great distances.
It’s also said that omitting a pitot tube (or any open chamber) can aid stealth operations.
The Future of Electronic Altimeters
Electronic altimeters are supplanting their predecessors, and in doing so, are becoming more integrated with computerized systems in numerous applications. The growing use of ICs and smaller components suggests they’ll become more capable over time—yet less intrusive.