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.
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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 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
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.
The public examination of the doctoral dissertation of Lingli Zhu will be held on 18 June 2015 at 12.00 at the Aalto University School of Engineering, Lecture hall M1, Otakaari 1, Espoo. The title of the dissertation is A Pipeline for 3D Scene Reconstruction from Point Clouds (Rakennetun ympäristön kolmiulotteinen mallintaminen pistepilvistä). Read more
A novel low-cost multi-sensor mobile laser scanning system has been developed at FGI CoE-LaSR by Anttoni Jaakkola. This work is the focus of his Dr. Sc. thesis, presented in the public examination on 5th June 2015 (Press release in Finnish).
“The results show that mobile laser scanning is a feasible method for various applications of mapping the environment and that even a low-cost system can perform sufficiently in these measurements” Anttoni Jaakkola concludes.
The developed system has been demonstrated on car and UAV (umanned aerial vehicle) platforms. It allows recognizing and classifying different features in the scanned environment, i.e. those of trees, roads and snow depth more accurately compared to the formerly used systems.
With future advances of laser scanning and positioning technologies, it can be expected that price of these systems will further decrease. Widespread adoption of laser scanners, especially in the automotive industry and the new global navigation satellite systems, will significantly reduce the cost of mobile laser scanning components. Nowadays expensive mobile laser scanning systems are almost exclusively owned by mapping companies as benefits of using them requires high rates of utilization and applications with high added-value.
“With future cost reduction, mobile laser scanning will expand to new fields, as also other companies can afford to acquire such systems and utilize them in various applications.” Jaakkola foresees.
Mobile laser scanning is a measurement technology that combines accurate positioning and attitude information from navigation satellites and inertial sensors with distance measurements from a laser scanner into a point cloud that represents the geometry of the environment surrounding the measurement platform. This geometrical information can be utilized in a variety of applications ranging from 3D city modelling and infrastructure maintenance to forestry and environmental monitoring.
Picture: Anttoni Jaakkola (left) demonstrating the UAV mobile laser scanning system
More information: Senior Research Scientist Anttoni Jaakkola, anttoni.jaakkola(at)nls.fi, tel 358 50 3498 108
A publication by Dr. Harri Kaartinen and his team is the top cited paper in the Remote Sensing journal in years 2012-2014. The article An International Comparison of Individual Tree Detection and Extraction Using Airborne Laser Scanning is based on the work the project “Tree Extraction” coordinated by CoE-LaSR researchers and organized by EuroSDR (European Spatial data Research) and ISPRS (International Society of Photogrammetry and Remote Sensing). The purpose of the project was to evaluate the quality, accuracy, and feasibility of automatic tree extraction methods, mainly based on laser scanner data.