Next up, LiDAR!

(first published in the UK Remote Sensing and Photogrammetry Society (RSPSoc) "Sensed" journal, January 2024: https://www.rspsoc.org.uk/index.php/publications/newsletter.html)

The commercial Earth observation data market gained traction with high resolution (1m) ground resolution optical data. OK, you could purchase commercial imagery at coarser resolution before then, but it wasn’t until higher resolution data came along that commercial EO started to expand as a business. Add some favourable (particularly U.S.) policy and softening regulation as to what can be flown by a private company and several companies focused on optical satellite operations emerged. Next came ways to bring costs down, both in satellite hardware and data storage: more capable smallsat technology and the advent of cloud computing significantly enabled much of the industry. But for a while the commercial industry was still centred on high resolution, high revisit optical imagery.

Over the last five years or so other commercial sensor typologies have started to emerge. As mentioned in a previous column, low-cost SAR has taken big steps forward – three companies have raised over $100 million in capital, and Iceye has over 30 satellite in-orbit. There are now four companies with their first hyperspectral satellites in-orbit. Both SAR and hyperspectral taking advantage of the ability to store and process very large datasets at a much-reduced cost than was possible only a few years ago.

Satellite-based LiDARs, however, are few. Just a handful of government operated research or Earth science satellites, such as ICESAT-2 have been launched. From a commercial perspective, the problem with LiDAR is not just around reducing CAPEX or data storage, but the science bit. LiDAR is “Light Detection And Ranging”, it is “active illumination”. Like radar it pulses a signal to Earth and collects the returned energy. The more energy that can be collected, the more information we can gather from Earth. And like radar data, from LiDAR we can derive information on heights of natural features or main made structures. The challenge of satellite-based LiDAR is that it is a lot easier to illuminate the Earth when closer to it. It is why most LiDAR solutions today are manned aerial, or UAV-based.

Taking further explanation from NOAA, “when a laser is pointed at a targeted area on the ground, the beam of light is reflected by the surface it encounters. A sensor records this reflected light to measure a range. When laser ranges are combined with position and orientation data, scan angles, and calibration data, the result is a dense, detail-rich group of elevation points, called a ‘point cloud’… The point clouds are used to generate products, such as digital elevation models (DEMs), Digital Surface Models (DSMs), canopy models, building models, contours etc.”

Herein is an advantage LiDAR has over elevation data from radar in that SAR-based solutions can only give DEM. To illustrate, LiDAR can give both the heights of the tree canopy, and the surface, whilst SAR can only give the canopy. In theory this means that with LiDAR it would be possible to work out biomass, or crop height etc. LiDAR is also more accurate; vertical heights can be measured to just a couple of centimeters in accuracy. However, the problem with aerial solutions in building commercial services is the inability to scale globally.

Whether a sensor is optical, SAR, hyperspectral or LiDAR, the pros and cons of aerial versus satellite are basically the same: aerial remote sensing will always be able to get to higher resolutions, greater sensor accuracy – but is limited by costs, coverage, revisit, and thus, the ability to scale solutions. Being able to image globally, at high coverage and with relatively low operational costs once in orbit is the satellite advantage. It is why today only about 5% of the Earth’s surface is mapped by aerial LiDAR.

As with any satellite sensor technology, aerial solutions are more complementary rather than competitive, and the experience in usage of aerial LiDAR means that the capability of the technology is relatively well understood. Theoretically, a satellite-based LiDAR would be able to scale the applications developed by aerial solutions. It would mean being able to answer questions on vegetation biomass, for carbon markets, or to work out crop yield. There are plenty of other application areas which would benefit from being able to understand heights or volumetrics at scale; from mining to defense, civil protection to environment and emissions monitoring and so on. For the U.S. Geological Survey, LiDAR is one of the key components to its “National Map” to deliver topographic information for the Nation. “It has many uses ranging from recreation to scientific analysis to emergency response”.? The LiDAR data is collected using aerial solutions, and at a significant cost.

Now enter commercial satellite solutions. At least two companies are currently looking at this problem, how to be able to illuminate the Earth from space and collect this data continuously from a satellite constellation: U.S.-based NUVIEW and Germany-based Airmo. The two companies diverge in their respective applications focus:

NUVIEW aims to build out a constellation of 20 commercial satellites outfitted with its proprietary lidar system.?Reportedly, some parts of its LiDAR system “have finally become commercially available after being the exclusive purview of the U.S. Department of Defense.” The company has raised $15 million to date (including investment from Leonardo di Caprio.) It will start by launching a “proof of concept” satellite called “Mr. Spoc,” followed by the roll-out of its constellation. NUVIEW states that it has over a billion dollars’ worth of “early adopter agreements.” It expects its biggest market will be in national mapping for global civil agencies.

AIRMO plans to launch its first satellite equipped with a spectrometer and a “micro-LiDAR” in late 2024; a full constellation of 12 satellites will follow. It has raised $5.7 million in pre-seed funding to support its constellation development. The company will use LiDAR to support the measurement of atmospheric carbon dioxide and methane, using the data combined with optical imagery.

Both these companies have some way to go in developing technology and raising funds. But scalable, global, satellite-based LiDAR by the end of the decade is a very real possibility.