Measuring an entire countries forest is no easy feat.
The forests of Europe are among the most closely monitored ecosystems on the planet. Yet, as the need for more accurate, detailed, and repeatable forest data grows, traditional methods of inventorying trees, tapes, callipers, and clinometers, are reaching their limits. Laser scanning technologies, particularly Terrestrial Laser Scanning (TLS) and Mobile Laser Scanning (MLS), are now redefining what forest measurement can mean.
In their 2025 paper published in Remote Sensing of Environment, Holvoet et al. explore how TLS and MLS can move from research experiments to operational tools within National Forest Inventories (NFIs), the backbone of forest resource monitoring across Europe. Drawing on three case studies in France, Finland, and Switzerland, the authors outline both the promise and the practical challenges of integrating 3D laser scanning into national-scale forest assessments.
National Forest Inventories are designed to take the pulse of a nation’s forests, monitoring tree growth, species composition, health, and carbon storage. Traditionally, these inventories have relied on field teams measuring a set of standard variables: tree height, diameter at breast height (DBH), and timber volume. But as NFIs expand to track biodiversity, ecosystem services, and climate-related variables, their data needs have become more complex.
Laser scanning offers a way to meet those demands. By emitting millions of laser pulses per second, TLS and MLS systems capture highly detailed 3D point clouds of trees, branches, and understory vegetation. These dense datasets can then be transformed into quantitative models of tree structure, biomass, and even crown architecture, all with sub-centimetre precision. TLS instruments, typically mounted on tripods, provide stable, high-resolution scans from fixed positions. MLS systems, in contrast, are mounted on backpacks or handheld devices, enabling fast and flexible data collection through forests. Together, they promise to revolutionize forest monitoring, not by replacing field crews, but by augmenting traditional surveys with richer, reproducible, and scalable information.
To understand what operational implementation looks like, Holvoet and colleagues examined three pioneering NFIs.
In France, TLS was first tested between 2010 and 2019 as part of the national inventory. Using portable FARO scanners, researchers scanned more than 1,500 plots across the country, capturing 20,000 individual trees from nearly 200 species. The goal was to improve species-specific volume equations and develop a database of 3D tree models. Early experiments revealed inconsistencies in data quality, mainly due to occlusion, where trees or branches blocked the scanner’s line of sight. To read more about the problem of occlusion, check out another article on this site. A revised protocol in 2016 improved results by focusing on leaf-off conditions and increasing the number of scan positions. The effort demonstrated that TLS could achieve DBH accuracies within 6% of manual measurements and precise tree volume estimates when combined with advanced modelling algorithms.
In Finland, TLS was deployed to refine tree volume and taper curve models used in national reporting. Between 2017 and 2018, 568 plots were scanned with Leica P40 instruments, producing detailed 3D models of Scots pine, Norway spruce, and birch. The Finnish team achieved stem volume accuracies within 5% of destructive reference measurements, a remarkable level of precision. However, field operations proved time-intensive, and dense canopies increased occlusion, particularly for tall trees. Despite these challenges, the project yielded updated volume models that better captured the form and variability of Finnish tree species.
Switzerland, meanwhile, is moving one step further. The Swiss NFI has been testing handheld MLS systems since 2019, aiming for full implementation in its next inventory cycle in 2027. Using GeoSLAM ZEB Horizon scanners, operators walk a regular grid path across 50 m × 50 m plots, collecting data in just 10 to 15 minutes. These MLS datasets allow the Swiss team to expand measurements beyond small circular plots, capturing entire stand structures, deadwood, and regeneration patterns. Early trials have shown that MLS can provide analysis-ready point clouds even in steep or dense terrain, offering a practical compromise between speed and accuracy.
As the case studies show, turning laser scanning from theory into practice is no small feat. Holvoet et al. identify four categories of barriers: logistical, data quality, economic, and perceptual.
Logistics come first. Field teams already carry heavy gear into remote plots, and scanners add both weight and setup time. Weather also matters, rain, wind, or snow can distort scans, yet NFIs must keep tight schedules. Data processing poses another bottleneck: a single plot’s scans can produce gigabytes of data requiring powerful computers and skilled analysts.
Data quality introduces further complexity. Occlusion remains unavoidable, especially in dense or uneven terrain. Random gaps in coverage can be corrected statistically, but systematic bias, such as under-scanning certain forest types, risks distorting national estimates. Changing scanner models mid-inventory also raises concerns about data continuity over time.
Economics is another challenge. Equipping multiple field crews with high-end scanners, training personnel, and maintaining large data servers requires substantial investment. As the authors note, “The budget to keep a TLS and MLS campaign running must be assured in the long term to prevent acquisitions from being abandoned partway through.”
Finally, perception plays a role. Many foresters still trust traditional instruments and methods refined over decades. The shift to automated 3D measurements demands not only new workflows but also a cultural change, one that values digital precision alongside field expertise.
Despite these hurdles, Holvoet and colleagues argue that TLS and MLS should be viewed not as replacements for traditional NFIs but as enhancements. Their value lies in expanding what inventories can measure, from basic structure to crown morphology, habitat features, and even microhabitats for biodiversity assessment.
The authors recommend a gradual implementation strategy: first, conduct pilot campaigns to test workflows and train crews; next, run TLS or MLS surveys alongside traditional methods for at least one full inventory cycle to ensure continuity and calibration. Over time, hybrid inventories will build confidence and establish best practices.
Text is a summarization of a following paper:
Holvoet, J., Eichhorn, M.P., Giannetti, F., Kükenbrink, D., Liang, X., Mokroš, M., Novotný, J., Pitkänen, T.P., Puliti, S., Skudnik, M. and Stereńczak, K., 2025. Terrestrial and mobile laser scanning for national forest inventories: From theory to implementation. Remote Sensing of Environment, 329, p.114947. https://doi.org/10.1016/j.rse.2025.114947
Text is authored by Henry Cerbone – Department of Biology – University of Oxford