The main objective of Junttila’s thesis was to investigate the capabilities of multispectral terrestrial lidar in the detection and assessment of tree decline caused by different stressors. This was done by investigating the estimation of a remotely detectable indicator of tree decline, leaf water content (LWC).
The World’s forests are facing novel stress due to climate change. Pest insects and pathogens are shifting towards new latitudes and heat stress is resulting in increased tree mortality and more frequent forest fires globally. Uncertainty in estimating the magnitude of climate change induced forest and tree decline requires new methods for unbiased estimation of tree decline.
The dissertation contributes both to the development of an objective and automatable method for detecting and measuring tree decline in the field, and to the understanding of the relationship between LWC and tree decline with implications to remote sensing.
Due to the extremely high costs of visiting and exploring objects in space, such as the Moon, Mars and other planets, it is crucial to find the right tools and techniques for collecting high-quality data for research. This can be done by making experiments in comparable places on Earth.
Valuable information with LiDAR
The FINESSE scientists have been exploring the Craters of the Moon National Monument and Preserve (CRMO) in the Snake River Plain of Idaho. As a part of the cooperation CoE-LaSR research professor Antero Kukko has been performing technology demonstrations using an FGI originating backpack mobile laser scanning system Akhka-R3.
In a lava field environment the Lidar detects details often more precise than 1 cm point distribution revealing even tiny details of the surface. The collected data enables the producing of high-accuracy topographic maps and provides information on terrain roughness and morphology features of the surveyed area.
The Backpack system developed in FGI has proven to be an efficient tool for fast collection of precise information in lava fields. The findings indicate that in similar conditions, i.e. in Mars, terrestrial and mobile laser scanning are good options for collecting data for further analogy and exploration studies.
The FINESSE program is a consortium of more than 30 research scientists. Their goal is to generate strategic knowledge in preparation for the human and robotic exploration of the Moon, near-Earth asteroids (NEAs) and Phobos & Deimos.
The Finnish Geospatial Research Institute (FGI), Department of Remote Sensing and Photogrammetry invites applications for the position of Tenure track Professor in Disruptive Remote Sensing Technologies.
FGI is the coordinating research institute of The Centre of Excellence in Laser Scanning and has one of the best laser scanning and photogrammetry laboratories in the Europe. The Department of Remote Sensing and Photogrammetry offers an excellent opportunity to personal development and cutting edge research.
Main tasks of the Tenure track Professor include leadership of research, carrying out cutting edge research personally, leadership of demanding international and academic projects, acquisition of outside funding alone or in collaboration with other professors and group leaders and performing other expert and academic tasks in the field of disruptive remote sensing technologies.
The applications should be sent at the latest 28 Feb 2019 16:15 o’clock (Finnish Time) to firstname.lastname@example.org.
The potential of terrestrial laser scanning (TLS) in forest applications, both in industry and in national forest inventories (NFIs), has gained increasing awareness in the last two decades. Boosting this development, there has been tremendous research efforts and progress on the topic.
In 2014, a TLS benchmarking project was launched by the European Spatial Data Research Organization (EuroSDR) and hosted by the Finnish Geospatial Research Institute (FGI). 18 groups from Asia, Europe and North America have successfully processed the data and submitted their results for evaluation. Latest results of the work were published in ISPRS Journal of Photogrammetry and Remote Sensing along with open data on the sample plots.
Achievements and remaining barriers to TLS-based forest investigations
Terrestrial laser scanning is an effective technique for measuring forest plots. A terrestrial laser scanner automatically documents its surrounding environment in three-dimensional (3D) space with millions to billions of 3D points. The technology is anticipated to be practically used in forest in-situ observations, e.g. national forest inventories.
According to the benchmarking results, TLS is great at extracting forest attributes of trees that are recorded in the point cloud data. These attributes, i.e. diameter at breast height and stem curve estimates, can be measured at 1-2 cm accuracy level which is close to what is required in practical applications, e.g. national forest inventories. Remaining barriers are mainly from the occlusion effects that prevail and hard to eliminate in forests; therefore, attributes of trees such as tree heights are difficult to estimate.
Open data on sample plot pointclouds
The single- and multi-TLS data, as well as the reference data, of six sample plots of this benchmarking project can be downloaded from here.
The data is opened to anyone who is interested in TLS based forest investigation for non-commercial use. Since the reference information is also opened, users can evaluate their own feature extraction approaches and results by themselves, and compare their own results with the other results reported in the project publication. When making a publication based on the open data set, please reference the date source of the ISPRS journal paper International benchmarking of terrestrial laser scanning approaches for forest inventories (Liang et al 2018).
Getting ready for operational use
The results of this international benchmarking suggest that TLS as well as sophisticated automated algorithms are ready to be used in practice under easy forest conditions, e.g., forests with good visibility or single trees. The operational use of TLS in forest mensuration is a complex process. The current bottleneck is the lack of practical software and it requires time to develop such software. The emerging mobile and personal laser scanning (MLS/PLS) have the potential to solve the occlusion problems of TLS, but have yet to achieve similar accuracy . It is worth noting that TLS currently provides the best quality terrestrial point clouds in comparison with all other technologies, meaning that all the benchmarks labeled in the benchmarking results can also serve as a reference for other terrestrial point clouds sources.
More information: Research manager Xinlian Liang, firstname.lastname(a)nls.fi
Collaboration between researchers from the Department of Forest Sciences (University of Helsinki) and end users from industry, consulting, and governmental organizations, for example, has been one of the main aims when developing forest applications within the Centre of Excellence in Laser Scanning (CoE-LaSR). Department of Forest Sciences organized a seminar for stakeholders to present the latest research and results using laser scanning for precision forestry. The seminar also reached students and other faculty members from the Department of Forest Sciences apart from the researchers of the CoE-LaSR.
During the afternoon seminar, recent research related to especially TLS and its application in forest mapping and monitoring were presented. The topics included, among others, identifying dead wood, measuring and modelling tree structure and growth as well as health status and wood quality. Furthermore, presentations included experiences from tree species detection and use of augmented reality for harvester drivers.
Intriguing discussion between participants and presenters emerged especially towards the end of the seminar which continued with a panel discussion. The panelists represented Natural Resources Institute, the City of Helsinki, Metsähallitus, Tapio, Metsäteho, Stora Enso and Finnish Forestry Center, all utilizing either laser scanning or products based on laser scanning such as forest resource information. The panelists described how they see laser scanning in the field of forestry and forest sciences, and also pointed out where research efforts are still needed. These included improving accuracy of estimates for species-specific forest inventory attributes and tree-size distributions as well as logging recovery. In addition, measuring quality attributes such as branchiness from standing trees was seen as important research topic by forest industry.
Laser scanning research got recognition among the international media in 2016. Our “sleeping trees” findings and advances in mobile laser scanning gained international audiences both in scientific journals and popular news. Two articles by CoE -LaSR researchers were in the top 10 of GIM International magazine’s most read articles 2016, and a Coe – LaSR cooperation article on birch tree’s day-night cycles was listed as one of the 12 best science stories of the year by The New Scientist.
The articles in GIM International brought insight into topics of personal laser scanners (PLS) and unmanned aerial systems (UAS). The main interest and focus was on the development of new scanning systems and potential applications utilizing them in 3D data collection.
First high performance backpack system Akhka in spotlight
To our knowledge, the Akhka PLS system has been the first backpack system with such high data acquisition capability. After the publication of this article, an updated revision, AkhkaR3, has been released with even higher performance sensors.
New research fields for laser scanning for plant dynamics
The New Scientist story ’Trees seen resting branches while ‘asleep’ for the first time‘ illustrated a novel application of using the high potential of terrestrial laser scanning measurements in the field of chronobiology. The study, a joint international research collaboration with Dr. Eetu Puttonen from NLS FGI and TU Wien, clearly demonstrated circadian movements of silver birch branches and showed for the first time that lidar measurements can detect nocturnal physical changes in trees that resemble a resting or a sleeping pattern.
Above: Overnight movement of a small tree acquired with three different terrestrial laser scanners. Each frame represents the point clouds measured at the shown time with color. The point coloring shows the reflectance of each measured point that were calibrated using an external calibration target. The black point cloud shows the tree’s original posture at sunset.
The results were exciting as they support the use of high resolution terrestrial laser scanning in monitoring plant dynamics with short time intervals and in a non-destructive manner. Additionally, the laser scanning measurements can be scaled up to cover for example several full-grown trees of different species simultaneously with short preparation times.
Our novel Hyperspectral Terrestrial Laser Scanning (TLS) dataset has been published as open data.
The laser scanning point cloud dataset consists of 30 individual scans collected as a time series covering a 26 hour time frame. Each point in the laser scanning point cloud contains colour information from several different wavelengths. Ordinary laser scanning data has colour information from one wavelength.
Compared to traditional laser scanning data, hyperspectral data has advantages in for example target recognition and change detection, where it is possible to track changes of color of tree leaves, as in the data published. Also 3D RGB presentations can be produced from data without using separate camera. All laser scanners enable collecting data without external light source, also in the dark.
The data has been utilised in recent research on movement of a birch during a 26 hour period, where it was found out that trees ”sleep” during night. Click the picture below to see an animation on the movement of a tree:
More information: Dr. Eetu Puttonen, eetu.puttonen(a)nls.fi
Personal mobile mapping on a backpack (PLS) is a novel innovation from FGI. The application uses various technologies: GNSS-IMU positioning, laser scanning, digital photography and data driven algorithms for improving the positioning in often GNSS denied urban space. PLS allows rapid data collection of complex environment without compromising the data coverage, precision and accuracy of data. The approach is a flexible solution for varied situations and mapping tasks in urban space, and applicable to e.g. building façade reconstruction, street mapping, urban arboculture and change detection.
The research aims at development of modern surveying practices, investigates alternative system and sensor layouts and performance related issues as well as formulates automated data processes for 3D modeling and seeks for methods for improving geometric quality of data and data fusion.
More information: Dr. Antero Kukko, Antero.Kukko(a)nls.fi
Above: 3D geometry and imagery are collected simultaneously using backpack PLS providing an efficient tool for urban mapping.
Above: Point cloud data collected with backpack PLS captures building geometry fast in high details and accuracy.
Personal laser scanners (PLS) lead the way towards compact, agile and flexible solutions for mapping complex environments and challenging locations, such as rugged terrain and complicated urban structures. Our Akhka R2 backpack laser scanning system allows the operator to move in and around the scene while capturing the environment with millimetre precision. Read more about the latest development in the GIM International article Laser Scanner in a Backpack – The Evolution towards All-terrain Personal Laser Scanners.
Picture above: Preparing to collect terrestrial laser scanning data from old Norway spruce forest.
High detail remote sensing technologies, especially laser scanning, and their ability to measure 3D structure of the forest have revolutionized forest mapping and monitoring applications.
“For example in Finland, forest management practices have been based on intensive small-scale forestry because the forests are mainly privately-owned and the size of an average forest holding is relatively small. This creates demanding surroundings for the used remote sensing systems.” New CoE-doctor Ville Kankare says.
The main objective of Kankare’s Ph.D. thesis at the Department of forest sciences, University of Helsinki, was to develop high density laser scanning methodologies for individual tree-level forest mapping. The thesis was accepted in June 2015.
The results of this thesis indicate that high density laser scanning is a vital option for measuring the required individual tree-level attributes, such as tree biomass, timber assortments, quality and stem curve. This type of information will play an important role in the next generation’s forest resource mapping systems especially where the added value for the information is the highest.
The main goal in forest resource mapping is to produce accurate information about forest structure and resources for forest owners, managers and forest industry. The precise knowledge of the biomass (bioenergy potential), logging recoveries and the quality of the available timber plays an essential role for example
when forest owner request tenders for the planned forest management procedures or
when forest industry is optimizing the flow of raw material from forest to the final product.
“The economic value and profitability of forest holding rely on detailed and up-to-date information of forest structure and attributes.“ Kankare concludes.
Picture: Representation of the Scots pine forest measured with terrestrial laser scanning.
More information: Ph.D. Ville Kankare, ville.kankare( at )helsinki.fi