About the Terrestrial Laser Scanning International Interest Group (TLSIIG)
The Terrestrial Laser Scanning International Interest Group is a group of international researchers exploring the use of portable laser scanning instruments that scan and image natural targets, such as vegetation canopies, from a ground position. The primary objective of the group is to advance the understanding and application of terrestrial laser scanning of vegetation targets for multiple goals, including
- Automated measurement of parameters that describe forest structure, such as mean tree diameter, stem count density, canopy height, canopy cover, and leaf area index;
- Forest management, including silviculture and inventory;
- Calibration and validation of above-ground biomass estimates retrieved from airborne lidar and/or other forms of remotely sensed data;
- Monitoring of vegetation dynamics;
- Developing new scanning instruments, processing algorithms, and structural measurements for new applications.
A key long-term goal of the TLSIIG is to facilitate the development of low-cost, effective lidar scanning instruments for rapid and automated assessment of biomass as needed for global carbon inventory and management according to protocols of REDD+ and FAO.
The activities of the group center on:
- Calibration and Intercomparison
- Modeling Activities
- Software Tools
- Data Standards and Archiving
- New Data Products
- New Scanning Technologies
- Collaborative Activities
The primary objective of communication within the TLSIIG is to facilitate working together to further the science of terrestrial laser scanning for ecological and forestry applications. Communication activity includes:
- Gatherings. Gatherings at meetings of opportunity or local meetings that provide the opportunity to learn about the latest developments and exchange information about individual activities.
- Webinars. Internet-enhanced seminars that provide a focus on specific topics or activities of a particular research group.
- Web site. The TLSIIG web site, tlsiig.bu.edu, which serves as an information resource as well as a mechanism for community conversation.
- E-mail. The TLSIIG email list, email@example.com, which provides a rapid mechanism for communicating to the group in a direct, effective fashion.
Calibration and Intercomparison
Calibration and intercomparison activities provide the ability to compare the performance of instruments of similar or different manufacture as well as to test the suitability of instruments for particular applications, including the retrieval of vegetation structure properties from lidar scans. The TLSIIG promotes these activities, including:
- Lab measurements. Measurement clinics and loans of test instruments to assure the performance of instruments to manufacturers’ specifications, including power, stability, scanning fidelity, noise levels, etc.
- Test sites. Identification of international test sites for lidar scanning that represent a broad range of vegetation covers useful in testing instrument and algorithm performance.
- Field measurements. Field scanning at common test sites, as well as multi-instrument community scanning events.
- Ancillary data. Sharing of ancillary data, such as measurements of vegetation structure made by conventional means at test sites.
- Spectral data. Acquisition, documentation, and distribution of spectral reflectance data of natural scattering surfaces, particularly at wavelengths used by scanning lidars.
Models are an integral part of TLS applications. Physical, probabilistic, and statistical models are all used in the processing of TLS data, and TLS vegetation structure retrievals are used to drive biogeophysical models of Earth systems and cycles. Accordingly, the TLSIIG encourages the development and application of relevant models for TLS development and applications, including:
- Theory. The development and application of necessary theory, for example probabilistic models of occlusion effects used in processing algorithms.
- Radiative transfer models. Structure measurements made by TLS can provide parameters that drive physics-based models of radiative transfer, providing a loop of model development, measurement, and feedback.
- Simulation models. Development and application of computational simulations of light scattering in vegetation canopies to validate TLS data and both refine such models and validate TLS retrieval algorithms.
- Biogeochemical models. Application of TLS data and products to calibrate and support biogeochemical models, for example carbon cycle models and hydrologic models.
TLS data requires software tools to retrieve vegetation structure parameters, and the TLSIIG works to improve and develop new tools:
- Product algorithms. Development and comparison of algorithms to retrieve vegetation canopy structure parameters from TLS data, for example, the automatic measurement of tree diameters and stand mean diameter in forests.
- 3-D Tools. Use of commercial and shareware tools for visualization and analysis of point clouds of scattering events produced by TLS.
Data Standards and Archiving
Developing standardized methods of structuring and storing data and making data easily available broadens horizons and helps advance TLS as a field.
- Standards. Data standards facilitate the development of new tools and algorithms that can be used with data from multiple instrument types.
- Data sharing. Because TLS data are not, in general, widely available, the TLSIIG endeavors to provide ways to share data within the group and the scientific community at large. Sharing data provides new insights and applications and helps to move the field forward into new directions.
- Active archiving. By liaisons with outside organizations, such as the NASA-supported Distributed Active Archive Center for Biogeochemical Dynamics at the Oak Ridge National Laboratory (USA), the TLSIIG promotes the active archiving and distribution of TLS data with the group and to the broader scientific community.
- Supporting measurements. Since tools and algorithms are often validated against ancillary data, the TLSIIG encourages active archiving of these supporting measurements.
New Data Products
The TLSIIG supports the development of new products describing vegetation structure. Possible new products include:
- Clumping. Point clouds of scattering events, provided by TLS data, can place clumps of scattering material in 3D space, providing a new approach to measurements of clumping.
- Allometric equations. By merging multiple scans of single trees, 3D reconstructions could be used to measure woody and leafy volume nondestructively.
- Vegetation moisture content. Dual-wavelength lidars have the potential to measure vegetation moisture content by differential absorption of water at NIR and SWIR wavelengths.
New Scanning Technologies
The TLSIIG promotes and supports the development of new scanning technology, including development of new instruments and the repurposing of lidars designed for other purposes for vegetation applications.
- Dual-wavelength scanning. New noncommercial instruments are now demonstrating dual-wavelength technology, using lasers at wavelengths near 1064 and 1550 nm that exploit enhanced absorption of water in plant tissues at 1550 nm to separate leafy and woody tissue.
- Repurposing. Laser ranging and detection systems developed for industrial applications have the potential to provide effective lidar scanners for vegetation characterization.
- New technologies. White lasers for multispectral applications and 3D flash lidar imaging systems, exploiting very rapid readout of ranging signals as imaged by detector arrays, are examples of new technologies that are of interest to the TLSIIG.
The TLSIIG encourages and supports collaborative activities among its members in order to further its mission of advancement of terrestrial laser scanning. Collaborative activities include:
- Field campaigns. Data acquisition at test sites using multiple instruments, as supported by conventional ground measurements of forest structure and alternative data, such as airborne lidar, provides a rapid and effective way to calibrate and compare instruments and algorithms.
- Group proposals. Proposals for funding can gain added support when incorporating group members with different scanners and algorithms. The TLSIIG benefits from proposals for international cooperation and communication to advance its objectives.
- Lobbying. Making program managers and funding agencies aware of the group’s activities and progress can provide a favorable climate for proposal and funding for both the group and individual research groups.
An important part of the TLSIIG’s mission is to further education of young scientists as undergraduates, post-graduates, and postdoctoral fellows, as well as provide outreach to the broader scientific community.
- Teaching materials. The common development and sharing of teaching materials, such as course outlines, lecture notes, laboratory/practicum exercises, and similar materials, builds a body of common knowledge among TLS researchers and students as well.
- Engagement in research. Learning is enhanced by engaging in research and collaborating with peers and colleagues in finding solutions for common problems.
- Outreach. The TLSIIG endeavors to inform potential data users, including ecosystem modelers, radiative transfer modelers, silviculturalists, forest mensurationists and others, of the capabilities of TLS for their applications.
The TLSIIG promotes exchanges of researchers and equipment loans between groups as a way of enhancing collaboration and communication.
- Researchers. Exchanges of researchers between research groups advances communications and moves the field forward more rapidly. Exchanges may also enhance the understanding of vegetation types and conditions in different areas of the globe, leading to better development of theory and algorithms.
- Calibration equipment. Proper calibration requires laboratory equipment that can be costly and require training to use. The TLSIIG encourages loans and exchanges to facilitate calibration of instruments and development of common standards.
- Instrument cross-training and exchanges. Exchanges of researchers to build familiarity with different instruments can lead to instrument exchanges that contribute to better understanding of TLS theory and applications.