So what is Single-Photon / Geiger-mode Lidar all about?

During ILMF 2017 in Denver, Co, Leica Geosystems announced the SPL100 single-photon scanner. With this news we wanted to get to the bottom of what really separates conventional lidar systems with this new wave of scanners.

Single-Photon and Geiger-mode Lidar, two names for (essentially) the same thing. Leica’s new SPL100 Single-Photon lidar is joins the ranks of a new generation of Lidar systems designed to detect and count individual photons. This technology, initially led by Sigma Space Corporation (Sigma Terra), promises around 6 million points per section with up to 30 points per square metre. Leica argue that the sensor offers the lowest cost per data point for state and country-wide collection.

Single-Photon/Geiger-mode Lidar is predicted to take the 3D-mapping market by storm in the coming years,  disrupting many of the industries that are currently served by conventional lidar systems. This technology dramatically increases the number of points a single flight can collect, giving a serious increase in 3D-mapping productivity. They are designed to split a single laser pulse into multiple sub-pulses, received using segmented detectors.  The ground reflects photons from a larger area, and at a higher effective pulse rate compared to linear-mode lidar, meaning they can can capture data at nominal point densities up to about 20-30 points per square metre.

SP/GM Lidar technology could be very powerful if applied correctly to the right application, making it more suitable than conventional technologies in some cases. These new sensors have picked up interest from organisations that work in flood plain management, transportation, civil government, and more.

However this new technology doesn’t completely over rule older lidar systems as the older systems still have advantages over the new sensors. Experts have said conventional technologies like discrete-return and waveform-based lidar will always have their place on the market.  Linear-mode and waveform lidar have been improved through decades of use and development to offer low ranging errors, which enables them to promise accuracy in the range of 3-6cm, whereas the new technologies are closer to 5-10cm. This means, for jobs that require the highest accuracy, intensity information, and waveform analysis, conventional Lidar still comes out on top.

In addition, the price-tag of Single-Photon/Geiger-mode Lidars is currently prohibitive for many users, and have forced manufacturers to explore new business models, where users don’t have to own the sensors outright. The greater expense means that many companies will continue to use conventional technologies, until the price tag drops.

For forest mapping applications, Carbomap’s top interest, there are other factors which come into play. Single-Photon/Geiger-mode Lidars are unable to provide intensity data or waveform analysis. And therefore, as explained by the CTO of our partner Riegl, Dr. Andreas Ullrich, conventional lidar will provide the edge for forest mapping, where the ability of full-waveform Lidar to penetrate through the forest canopy is one of its key strengths. Carbomap believe that the ability to map not only the top surface of a forest sets waveform Lidar in a league of its own.

Full-waveform analysis is also still an ever evolving and improving technology, a recent example is our own contributions to the ability to process this data through Pulsewaves (you can find out more about this on our website). Therefore, whilst we watch these new developments of Single-Photon and Geiger-mode Lidars with excitement, we feel that Forest mapping in particular still favours the use full-waveform Lidar.

If you want to read some more about the latest developments at ILMF regarding Single-Photon and Geiger-mode Lidar you can download their free report here.

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