High-resolution airborne laser scanner data offer the possibility to detect and measure individual trees. In this study an algorithm which estimated position, height, and crown diameter of individu ...

Detecting and measuring individual trees using an airborne laser scanner

This paper reviews LiDAR ground filtering algorithms used in the process of creating Digital Elevation Models. We discuss critical issues for the development and application of LiDAR ground filtering algorithms, including filtering procedures for different feature types, and criteria for study site selection, accuracy assessment, and algorithm classification. This review highlights three feature types for which current ground filtering algorithms are suboptimal, and which can be improved upon in future studies: surfaces with rough terrain or discontinuous slope, dense forest areas that laser beams cannot penetrate, and regions with low vegetation that is often ignored by ground filters.

https://www.mdpi.com/2072-4292/2/3/833/pdf

Ground Filtering Algorithms for Airborne LiDAR Data: A Review of Critical Issues

This article reviews the research and application of airborne laser scanning for forest inventory in Finland, Norway and Sweden. The first experiments with scanning lasers for forest inventory were conducted in 1991 using the FLASH system, a full-waveform experimental laser developed by the Swedish Defence Research Institute. In Finland at the same time, the HUTSCAT profiling radar provided experiences that inspired the following laser scanning research. Since 1995, data from commercially operated time-of-flight scanning lasers (e.g. TopEye, Optech ALTM and TopoSys) have been used. Especially in Norway, the main objective has been to develop methods that are directly suited for practical forest inventory at the stand level. Mean tree height, stand volume and basal area have been the most important forest mensurational parameters of interest. Laser data have been related to field training plot measurements using regression techniques, and these relationships have been used to predict corresponding properti...

Laser scanning of forest resources: the nordic experience

Laser scanning provides a good means to collect information on forest stands. This paper presents an approach to delineate single trees automatically in small footprint light detection and ranging (lidar) data in deciduous and mixed temperate forests. In rasterized laser data possible tree tops are detected with a local maximum filter. Afterwards the crowns are delineated with a combination of a pouring algorithm, knowledge-based assumptions on the shape of trees, and a final detection of the crown-edges by searching vectors starting from the trees’ tops. The segmentation results are assessed by comparison with terrestrial measured crown projections and with photogrammetrically delineated trees. The segmentation algorithm works well for coniferous stands. However, the implemented method tends to merge crowns in dense stands of deciduous trees.

Detection of individual tree crowns in airborne lidar data

Estimating tree height and tree crown properties using airborne scanning laser in a boreal nature reserve

This paper evaluates and discusses the accuracy of laser scanner in DTM (digital terrain model) generation and digital 3-D height model generation in forested areas. High-pulse-rate laser scanners are capable of detecting single trees in a boreal forest zone, since a significant amount of the laser pulses reflect directly from the ground without any interaction with the canopy. This allows for a detailed investigation of forest areas and the creation of a 3-dimensional tree height model. Special emphasis is laid on the optimisation of the selection of ground hits used for the creation of the DTM of future high-pulse-rate laser scanners. A novel DTM algorithm is depicted in detail. In order to develop the algorithm, five phases were created: 1) Calculation of the original reference surface, 2) removal of the vegetation from the reference surface, 3) classificatio n of the original cloud of points, 4) calculation of the DTM based on the classified ground hits, and 5) interpolation of the missing points. A standard error of 15 cm was obtained for flat forest areas and the error increased with increasing terrain slope to the value of approximately 40 cm at the slope of 40 %. The average standard error for forest area was about 22 cm. The laser-derived DTM of the forest road deviated from the true height by 8.5 cm only. An optimum performance for the DTM generation was obtained by averaging the ground hits which were located, at the maximum, 60 cm above the minimum terrain values. It was also shown that tree heights of individual trees in the dominating storey can be obtained with less than 1 m standard error.

http://www.lidar.com.br/arquivos/targetmodelsforestenviroment.pdf

Elevation accuracy of laser scanning-derived digital terrain and target models in forest environment

The laser scanning technology has become de-facto as a successful measuring mean in numerous applications of remote sensing and mapping. A development of hardware has been followed by a development of a new data file format standard know as the American society for Photogrammetry and Remote Sensing (ASPRS) Lidar Exchange Format (LAS). This data format standard has been designed in order to make the exchange of lidar data, (pre-/post-) processing, analysis, and storing less time consuming and more convenient. There are three versions of the ASPRS LAS standard: 1.0, 1.1, and 2.0 (draft). A number of the manufacturers of hardware and software, laser scanning service providers and end users have already accepted a concept of ASPRS LAS as an industry standard. However, a less experienced end user might be confused by the different definitions of the term LAS that appear in literature and are used by various software vendors. The following main LAS definitions in remote sensing and geomatics exist: Land Analysis System by USGS, Log ASCII Standard by the Canadian Well Logging Society, LAS image format by ER Mapper, and ASPRS LAS by the ASPRS Lidar Committee. This paper explains the different common meanings of those terms. Several popular software products used for lidar data processing are also reviewed and the terminology associated with the file format defined. At this time there is no common tool available for converting from one ASPRS LAS format to another, and this can be a challenge when working with multiple formats. Only in one study case a version number of ASPRS LAS was clearly identified in the Import/Export tool. This paper also provides a comparison feature matrix of the different versions of ASPRS LAS.

/pdf/an-implementation-of-the-asprs-las-standard-6enbxlep8x.pdf

An implementation of the asprs las standard

The increasing demand on accurately monitoring various pollutions, especially, oil in seawater and in ice, requires the employment of advanced remote sensing means. These techniques must be real-time and suitable for multiple tasks. One of very promising oil remote sensing techniques is a hyperspectral analyze of a laser light reflected by oil film. There is some development work going on in the world. This activity focuses on a modern lidar system, which is called a multi-wavelength hyperspectral lidar system. Our paper provides an overview of state-of-art of hyperspectral lidar technology up-to-date.

Advanced oil pollution detection using an airborne hyperspectral lidar technology

The stem volume, basal area and mean height of Norway spruce and Scots pine stands and individual trees were derived using canopy height metrics by means of a laser scanner TopoSys-1. Due to the high pulse rate of the laser scanner, individual tree statistics could be obtained. Methods to generate DTM and tree crown map from laser data were reported. Stand-wise and tree-wise field inventory data was regressed against laser-derived features. The coefficients of determination were in the range between 0.84 and 0.88 for the stem volume, basal area and mean height. The obtained accuracy was equivalent to conventional stand-wise forest inventory implying that the described approach can be used operationally. Further, it was shown that the tree height estimation accuracy of single and dominant trees was 1.5 m using the laser scanner. The accuracy of conventional clinometer measurements is typically better than 0.5 m but the time spent for height measurements is enormous. With the laser, the height of all dominant trees could be assessed within a fraction of time.

Assessing forest stand attributes by laser scanner

Since the beginning of the 21st century, there has been an increasing interest in merging data acquired simultaneously by lidar and hyperspectral sensors. There are two major reasons for this interest. First, a laser works as an artificial light source that expands the operating range of optical remote sensing systems. Second, a hyperspectral detector is adjusted to specific spectral feature(s) of the scene due to the operating wavelength(s) of the laser light source. This simplified approach allows us to ignore extra information coming from a passive hyperspectral sensor and therefore greatly speeds up the decision-making process. This study was motivated by the absence of sufficient information about active optical remote sensing means in the literature, which is widely used in remote sensing education and image interpretation. This paper provides an overview of the state-of-the-art of airborne laser systems for oil mapping. Resume. Depuis le debut du 21 e siecle, i lyau n interet accru pour la fusion des donnees acquises simultanement par des capteurs lidar et hyperspectraux. Cet interet peut s'expliquer par deux motifs principaux. Premierement, un laser agit comme source de lumiere artificielle, ce qui accroit le champ d'exploitation des systemes de teledetection optique. Deuxiemement, un detecteur hyperspectral s'ajuste aux caracteristiques spectrales specifiques de l'image grâce aux longueurs d'onde d'exploitation de la source de lumiere laser. Cette approche simplifiee permet d'ignorer l'information additionnelle provenant d'un capteur hyperspectral passif accelerant ainsi le processus de prise de decision. Notre etude a ete motivee par l'absence d'information suffisante concernant les methodes de teledetection optique active dans la litterature couramment utilisee pour la formation en teledetection et en interpretation des images. Cet article donne un apercu de l'etat de l'art dans le domaine des systemes laser aeroportes pour la cartographie des hydrocarbures. (Traduit par la Redaction) Samberg 149

Andre Samberg

Papers

Elevation accuracy of laser scanning-derived digital terrain and target models in forest environment

An implementation of the asprs las standard

Advanced oil pollution detection using an airborne hyperspectral lidar technology

Assessing forest stand attributes by laser scanner

The state-of-the-art of airborne laser systems for oil mapping