scholarly journals HEIGHT, DIAMETER AND TREE CANOPY COVER ESTIMATION BASED ON UNMANNED AERIAL VEHICLE (UAV) IMAGERY WITH VARIOUS ACQUISITION HEIGHT

2021 ◽  
Vol 26 (1) ◽  
pp. 17-27
Author(s):  
Muflihatul Maghfiroh Islami ◽  
Teddy Rusolono ◽  
Yudi Setiawan ◽  
Aswin Rahadian ◽  
Sahid Agustian Hudjimartsu ◽  
...  
Keyword(s):  
Forest Inventory ◽  
Canopy Cover ◽  
Tree Height ◽  
Tree Canopy ◽  
Flying Height ◽  
Stand Age ◽  
Digital Terrain ◽  
Terrain Models ◽  
Surface Models ◽  
Aerial Vehicle

The forest inventory technique by applying remote sensing technology has become a new breakthrough in technological developments in forest inventory activities. Unmanned Aerial Vehicle (UAV) imagery with camera sensor is one of the inventory tools that produce data with high spatial resolution. The level of spatial resolution of the image is strongly influenced by the flying height of the UAV for a certain camera’s focus. In addition, flight height also affects the acquisition time and accuracy of inventory results, although there is still little research on this matter. The study aims to (a)evaluate the effect of various flying heights on the accuracy of tree height measurements through UAV imagery for every stand age class, (b).estimate the trees diameter and canopy cover for every stand age class. Stand height was estimated using Digital Surface Models (DSM), Digital Terrain Models (DTM) and Orthophoto. DSM and DTM were built by converting orthophoto to pointclouds using the PIX4Dmapper based on Structure From Motion (SFM) on the photogrammetric method to reconstruct topography automatically. Meanwhile, the tree cover canopy was estimated using the All Return Canopy Index (ARCI) formula. The results show that the flight height of 100 meters produces a stronger correlation than the flying height of 80 meters and 120 meters in estimating tree height, based on the high coefficient of determination (R2) and the low root mean square error (RMSE) value. In addition, tree canopy estimation analysis using ARCI has a maximum difference of 9.8% with orthophoto visual delineation.  Key words: canopy height model (CHM), digital surface models (DSM), digital terrain models (DTM), forest inventory, UAV image

scholarly journals Development and Performance Evaluation of a Very Low-Cost UAV-Lidar System for Forestry Applications

2020 ◽  
Vol 13 (1) ◽  
pp. 77
Author(s):  
Tianyu Hu ◽  
Xiliang Sun ◽  
Yanjun Su ◽  
Hongcan Guan ◽  
Qianhui Sun ◽  
...  
Keyword(s):  
Forest Inventory ◽  
Low Cost ◽  
Canopy Cover ◽  
Tree Height ◽  
Flying Height ◽  
Tree Level ◽  
Forest Site ◽  
Lidar System ◽  
Individual Tree ◽  
Gap Fraction

Accurate and repeated forest inventory data are critical to understand forest ecosystem processes and manage forest resources. In recent years, unmanned aerial vehicle (UAV)-borne light detection and ranging (lidar) systems have demonstrated effectiveness at deriving forest inventory attributes. However, their high cost has largely prevented them from being used in large-scale forest applications. Here, we developed a very low-cost UAV lidar system that integrates a recently emerged DJI Livox MID40 laser scanner (~$600 USD) and evaluated its capability in estimating both individual tree-level (i.e., tree height) and plot-level forest inventory attributes (i.e., canopy cover, gap fraction, and leaf area index (LAI)). Moreover, a comprehensive comparison was conducted between the developed DJI Livox system and four other UAV lidar systems equipped with high-end laser scanners (i.e., RIEGL VUX-1 UAV, RIEGL miniVUX-1 UAV, HESAI Pandar40, and Velodyne Puck LITE). Using these instruments, we surveyed a coniferous forest site and a broadleaved forest site, with tree densities ranging from 500 trees/ha to 3000 trees/ha, with 52 UAV flights at different flying height and speed combinations. The developed DJI Livox MID40 system effectively captured the upper canopy structure and terrain surface information at both forest sites. The estimated individual tree height was highly correlated with field measurements (coniferous site: R2 = 0.96, root mean squared error/RMSE = 0.59 m; broadleaved site: R2 = 0.70, RMSE = 1.63 m). The plot-level estimates of canopy cover, gap fraction, and LAI corresponded well with those derived from the high-end RIEGL VUX-1 UAV system but tended to have systematic biases in areas with medium to high canopy densities. Overall, the DJI Livox MID40 system performed comparably to the RIEGL miniVUX-1 UAV, HESAI Pandar40, and Velodyne Puck LITE systems in the coniferous site and to the Velodyne Puck LITE system in the broadleaved forest. Despite its apparent weaknesses of limited sensitivity to low-intensity returns and narrow field of view, we believe that the very low-cost system developed by this study can largely broaden the potential use of UAV lidar in forest inventory applications. This study also provides guidance for the selection of the appropriate UAV lidar system and flight specifications for forest research and management.

scholarly journals ASSESSING FLOOD IMPACTS IN RURAL COASTAL COMMUNITIES USING LIDAR

2016 ◽  
Vol XLI-B8 ◽  
pp. 1135-1139
Author(s):  
E. S. Johnson
Keyword(s):  
Storm Surges ◽  
Coastal Communities ◽  
Lidar Data ◽  
Storm Events ◽  
Flood Events ◽  
Flood Impacts ◽  
Digital Terrain ◽  
Terrain Models ◽  
Surface Models ◽  
Coastal Residents

Coastal communities are vulnerable to floods from storm events which are further exacerbated by storm surges. Additionally, coastal towns provide specific challenges during flood events as many coastal communities are peninsular and vulnerable to inundation of road access points. Publicly available lidar data has been used to model areas of inundation and resulting flood impacts on road networks. However, these models may overestimate areas that are inaccessible as they rely on publicly available Digital Terrain Models. Through incorporation of Digital Surface Models to estimate bridge height, a more accurate model of flood impacts on rural coastal residents can be estimated.

Impact of Eidolon helvum on roost trees on UENR campus

2018 ◽  
Vol 2 (2) ◽  
pp. 44-50
Author(s):  
E. Danquah
Keyword(s):  
Tree Species ◽  
Diversity Index ◽  
Canopy Cover ◽  
Basal Area ◽  
Tree Height ◽  
Tectona Grandis ◽  
Tree Canopy ◽  
Species Diversity Index ◽  
Tree Canopy Cover ◽  
Occupied Zone

Four sample plots, each of size 20m by 20m were systematically distributed in two strata (i.e. two plots in bat-occupied zone andthe remaining two plots in bat-unoccupied zone, to serve as control units). Using six (20m × 20m) sample plots each, basal area,canopy, and heights of trees with DBH 1m were measured. Fourteen individual trees were recorded in the bat-unoccupied zone,resulting in only seven tree species. On the other hand, 16 tree species, corresponding to a total of 25 trees were recorded in thebat occupied zone. Albizia zygia, Antiaris toxicaria, Azadiractha indicia, Holarrhena floribunda, Morinda lucinda, and Sterculiatragacantha were common to both zones. The Shannon Wiener species diversity index was found to be higher (H1=1.92) in batoccupied zones and lower (H1=1.45) in bat-unoccupied zone. Estimates of tree basal area and tree height were much higherin bat occupied zones compared to bat-unoccupied zones. (Mann-Whitney U test: U = 573.0, p < 0.05), tree basal area (U= 674.0, p < 0.05), tree height (U = 632.0, p < 0.05) and tree canopy cover (U = 329.0, p < 0.05). Holarrhena floribunda(0.34 m2/h) and Ceiba pentandra (0.22m2/ha) contributed the largest basal area (32.94% of the total basal area) whilst Sennasiamea (0.01m2/ha) and Tectona grandis (0.01m2/ha) yielded the smallest basal area (1.17%). In general, bats seem to greatlypatronize areas with higher densities of tall trees than relatively open areas with shorter trees.

Countrywide surface models from historical panchromatic and true color stereo imagery – a retrospective analysis of forest structures in Switzerland

2020 ◽  
Author(s):  
Christian Ginzler ◽  
Mauro Marty ◽  
Lars T. Waser
Keyword(s):  
Forest Inventory ◽  
Digital Terrain Model ◽  
National Forest Inventory ◽  
Aerial Images ◽  
National Forest ◽  
Terrain Model ◽  
Digital Terrain ◽  
Surface Models ◽  
Stereo Imagery ◽  
True Color

&lt;p&gt;&lt;strong&gt;Countrywide surface models from historical panchromatic and true color stereo imagery &amp;#8211; a retrospective analysis of forest structures in Switzerland&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Mauro Marty&lt;sup&gt;1&lt;/sup&gt;, Lars T. Waser&lt;sup&gt;1&lt;/sup&gt;, Christian Ginzler&lt;sup&gt;1&lt;/sup&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&lt;/sup&gt; Swiss Federal Institute for Forest, Snow and Landscape Research WSL, &lt;br&gt;Z&amp;#252;rcherstrasse 111, CH - 8903 Birmensdorf, Switzerland&lt;/p&gt;&lt;p&gt;Remote sensing methods allow the acquisition of 3D structures of forests over large areas. Active systems, such as Airborne Laser Scanning (ALS) and Synthetic Aperture Radar (SAR) and passive systems, such as multispectral sensors, have been established to acquire 3D and 2.5D data of the earth's surface. Nationwide calculations of surface models with photogrammetric methods from digital stereo aerial images or ALS data are already in operation in some countries (e.g. Switzerland, Austria, some German states).&lt;/p&gt;&lt;p&gt;The availability of historical stereo aerial images allows the calculation of digital surface models from the past using photogrammetric methods. We present a workflow with which we have calculated nationwide surface models for Switzerland for the 1980s, 1990s and 2000s. Current surface models are available from the National Forest Inventory (LFI) Switzerland.&lt;/p&gt;&lt;p&gt;In the context of the Swiss land use and land cover statistics, the Federal Office of Topography (swisstopo) scanned and oriented the analogue black and white stereo aerial photographs with a mean scale of ~1:30'000 of the nationwide flights of 1979 - 84 and1993 - 1997 with 14 &amp;#181;m. The true colour image data from 1998 &amp;#8211; 2007 were scanned for the production of the orthoimages swissimage by swisstopo. All these data &amp;#8211; the scanned images and the orientation parameters - are also available to the National Forest Inventory (NFI). Within the framework of the NFI, we developed a highly automated workflow to generate digital surface models (DSMs) from many thousands of overlapping frame images covering the whole country. In total, more than 25'000 individual stereo models were processed to nationwide surface models. For their normalization, the digital terrain model of Switzerland 'swissAlti3D' was used. As the image orientation in some areas showed high vertical inaccuracies, corrections had to be made. Data from the Swiss land use and land cover statistics were used for this purpose. At places with constant surface cover since the 1980s (e.g. grassland), correction grids were calculated using the digital terrain model and applied to the surface models.&lt;/p&gt;&lt;p&gt;The results are new data sets on the 2.5D surface of Switzerland from the 1980s, 1990s and 2000s with a high spatial resolution of 1 m. It can be stated that the completeness of the image correlation in forested areas was quite satisfactory. In open areas with agricultural land, however, the matching points were often reduced to the road network, as the meadows and fields in the scanned SW stereo aerial images had very little texture.&lt;/p&gt;&lt;p&gt;This new historical, nationwide data on the horizontal and vertical structure in forests now allows their analysis of changes over the last 40 years.&lt;/p&gt;

scholarly journals Determining the Variability of the Territorial Sea Baseline on the Example of Waterbody Adjacent to the Municipal Beach in Gdynia

2019 ◽  
Vol 9 (18) ◽  
pp. 3867 ◽  
Author(s):  
Specht ◽  
Specht ◽  
Wąż ◽  
Dąbrowski ◽  
Skóra ◽  
...  
Keyword(s):  
Temporal Variability ◽  
Satellite System ◽  
Spatial And Temporal Variability ◽  
Position Change ◽  
Digital Terrain ◽  
Terrain Models ◽  
Sea Bottom ◽  
Surface Models ◽  
Global Navigation Satellite ◽  
Sand Bottom

The purpose of this publication is to analyze the spatial and temporal variability of the territorial sea baseline in sand bottom waterbodies, which were determined twice, in 2016 and 2018, by the Real Time Kinematic (RTK) method. This involves direct measurement of sea bottom coordinates on planned hydrographic sounding profiles using a Global Navigation Satellite System (GNSS) receiver mounted on a pole. The data were the basis for creating Digital Terrain Models (DTM), which were then used to determine the baseline for both measurement campaigns. Subsequently, terrain surface models were compared to determine bathymetry changes in the area under analysis, and an assessment was made of the baseline spatial position change over the previous two years. The measurements have shown considerable spatial and temporal variability of the baseline course along a short section of sandy beach. The territorial sea baseline was very unstable; in some places, it moved by even 20–25 m, landwards and seawards. Therefore, one can suppose that these changes are periodic, and one can conclude that the reliability of the baseline measurements can decrease quite quickly.

scholarly journals Photogrammetric 3D Model via Smartphone GNSS Sensor: Workflow, Error Estimate, and Best Practices

2020 ◽  
Vol 12 (21) ◽  
pp. 3616
Author(s):  
Stefano Tavani ◽  
Antonio Pignalosa ◽  
Amerigo Corradetti ◽  
Marco Mercuri ◽  
Luca Smeraglia ◽  
...  
Keyword(s):  
3D Model ◽  
Model Building ◽  
Satellite System ◽  
Test Case ◽  
Digital Terrain ◽  
Ground Control Points ◽  
Terrain Models ◽  
Aerial Vehicle ◽  
Global Navigation Satellite ◽  
The Impact

Geotagged smartphone photos can be employed to build digital terrain models using structure from motion-multiview stereo (SfM-MVS) photogrammetry. Accelerometer, magnetometer, and gyroscope sensors integrated within consumer-grade smartphones can be used to record the orientation of images, which can be combined with location information provided by inbuilt global navigation satellite system (GNSS) sensors to geo-register the SfM-MVS model. The accuracy of these sensors is, however, highly variable. In this work, we use a 200 m-wide natural rocky cliff as a test case to evaluate the impact of consumer-grade smartphone GNSS sensor accuracy on the registration of SfM-MVS models. We built a high-resolution 3D model of the cliff, using an unmanned aerial vehicle (UAV) for image acquisition and ground control points (GCPs) located using a differential GNSS survey for georeferencing. This 3D model provides the benchmark against which terrestrial SfM-MVS photogrammetry models, built using smartphone images and registered using built-in accelerometer/gyroscope and GNSS sensors, are compared. Results show that satisfactory post-processing registrations of the smartphone models can be attained, requiring: (1) wide acquisition areas (scaling with GNSS error) and (2) the progressive removal of misaligned images, via an iterative process of model building and error estimation.

scholarly journals Wiederholungsaufnahmen als Instrument zur Qualitätssicherung im Schweizerischen Landesforstinventar

2016 ◽  
Vol 167 (3) ◽  
pp. 118-127 ◽  
Author(s):  
Berthold Traub ◽  
Fabrizio Cioldi ◽  
Christoph Düggelin
Keyword(s):  
Forest Inventory ◽  
Stand Structure ◽  
Tree Height ◽  
National Forest Inventory ◽  
Stand Age ◽  
National Forest ◽  
Stage Of Development ◽  
Statistical Measures ◽  
Expected Values ◽  
Stand Attributes

Repeat surveys as a quality assurance tool in the Swiss National Forest Inventory The Swiss National Forest Inventory (NFI) repeats surveys to guarantee the quality of fieldwork. To this end, approximately 10% of sample plots are completely surveyed a second time over a field season. Based on the results of the repeat survey, the current investigation focuses on the assessment precision, i.e. the reproducibility of various tree and stand attributes in NFI4. It also investigates whether the change from periodic (NFI1–NFI3) to continuous (NFI4) fieldwork has had a positive effect on the reproducibility of the attributes. The current results of the repeat surveys for NFI4 (2009/2017) are compared with those for NFI3 (2004/2006) to this end. We used statistical measures as well as measurement quality objectives (MQO) set by the NFI instructor team as a reference for evaluating reproducibility. The results vary for tree attributes which are vital for estimating stock. The result for the diameter at breast height (dbh) corresponds to the expected values, while that for upper stem diameter at seven meters height and tree height were approximately 5% below the expected values. With regard to the seven stand attributes also analyzed, four of them exceeded the quality goals (stand age, stand stability, the degree of cover of secured regeneration, and stage of development). The results for the mixture proportion, the stand structure and crown closure were between 5 and 18% below MQO. The result for presence of woody species shows that the recording of larger plants (above 130 cm) is clearly more reproducible than for smaller plants (40–130 cm). In NFI4, the reproducibility for almost all studied attributes was improved. The results suggest that the modified structure of fieldwork (with only three field teams and continuous fieldwork in NFI4) has a positive influence on the reproducibility of the included attributes.

scholarly journals Drone Laser Scanning for Modeling Riverscape Topography and Vegetation: Comparison with Traditional Aerial Lidar

Drones ◽  
2019 ◽  
Vol 3 (2) ◽  
pp. 35 ◽  
Author(s):  
Jonathan P. Resop ◽  
Laura Lehmann ◽  
W. Cully Hession
Keyword(s):  
Laser Scanning ◽  
Point Clouds ◽  
Lidar Data ◽  
Lower Altitude ◽  
Aerial Laser Scanning ◽  
Digital Terrain ◽  
Terrain Models ◽  
Data Points ◽  
Aerial Vehicle ◽  
Complete Survey

Lidar remote sensing has been used to survey stream channel and floodplain topography for decades. However, traditional platforms, such as aerial laser scanning (ALS) from an airplane, have limitations including flight altitude and scan angle that prevent the scanner from collecting a complete survey of the riverscape. Drone laser scanning (DLS) or unmanned aerial vehicle (UAV)-based lidar offer ways to scan riverscapes with many potential advantages over ALS. We compared point clouds and lidar data products generated with both DLS and ALS for a small gravel-bed stream, Stroubles Creek, located in Blacksburg, VA. Lidar data points were classified as ground and vegetation, and then rasterized to produce digital terrain models (DTMs) representing the topography and canopy height models (CHMs) representing the vegetation. The results highlighted that the lower-altitude, higher-resolution DLS data were more capable than ALS of providing details of the channel profile as well as detecting small vegetation on the floodplain. The greater detail gained with DLS will provide fluvial researchers with better estimates of the physical properties of riverscape topography and vegetation.

scholarly journals Assessment of Individual Tree Detection and Canopy Cover Estimation using Unmanned Aerial Vehicle based Light Detection and Ranging (UAV-LiDAR) Data in Planted Forests

2019 ◽  
Vol 11 (8) ◽  
pp. 908 ◽  
Author(s):  
Xiangqian Wu ◽  
Xin Shen ◽  
Lin Cao ◽  
Guibin Wang ◽  
Fuliang Cao
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Forest Inventory ◽  
Canopy Cover ◽  
Light Detection And Ranging ◽  
Estimation Methods ◽  
Lidar Data ◽  
Tree Crown ◽  
Polynomial Fitting ◽  
Individual Tree ◽  
Aerial Vehicle

Canopy cover is a key forest structural parameter that is commonly used in forest inventory, sustainable forest management and maintaining ecosystem services. Recently, much attention has been paid to the use of unmanned aerial vehicle (UAV)-based light detection and ranging (LiDAR) due to the flexibility, convenience, and high point density advantages of this method. In this study, we used UAV-based LiDAR data with individual tree segmentation-based method (ITSM), canopy height model-based method (CHMM), and a statistical model method (SMM) with LiDAR metrics to estimate the canopy cover of a pure ginkgo (Ginkgo biloba L.) planted forest in China. First, each individual tree within the plot was segmented using watershed, polynomial fitting, individual tree crown segmentation (ITCS) and point cloud segmentation (PCS) algorithms, and the canopy cover was calculated using the segmented individual tree crown (ITSM). Second, the CHM-based method, which was based on the CHM height threshold, was used to estimate the canopy cover in each plot. Third, the canopy cover was estimated using the multiple linear regression (MLR) model and assessed by leave-one-out cross validation. Finally, the performance of three canopy cover estimation methods was evaluated and compared by the canopy cover from the field data. The results demonstrated that, the PCS algorithm had the highest accuracy (F = 0.83), followed by the ITCS (F = 0.82) and watershed (F = 0.79) algorithms; the polynomial fitting algorithm had the lowest accuracy (F = 0.77). In the sensitivity analysis, the three CHM-based algorithms (i.e., watershed, polynomial fitting and ITCS) had the highest accuracy when the CHM resolution was 0.5 m, and the PCS algorithm had the highest accuracy when the distance threshold was 2 m. In addition, the ITSM had the highest accuracy in estimation of canopy cover (R2 = 0.92, rRMSE = 3.5%), followed by the CHMM (R2 = 0.94, rRMSE = 5.4%), and the SMM had a relative low accuracy (R2 = 0.80, rRMSE = 5.9%).The UAV-based LiDAR data can be effectively used in individual tree crown segmentation and canopy cover estimation at plot-level, and CC estimation methods can provide references for forest inventory, sustainable management and ecosystem assessment.

Aerial thermography from low-cost UAV for the generation of thermographic digital terrain models

2015 ◽  
Vol 23 (1) ◽  
Author(s):  
S. Lagüela ◽  
L. Díaz−Vilariño ◽  
D. Roca ◽  
H. Lorenzo
Keyword(s):  
Low Cost ◽  
Digital Terrain Model ◽  
Thermal Response ◽  
Energy Performance ◽  
Medium Size ◽  
Heat Islands ◽  
Terrain Model ◽  
Digital Terrain ◽  
Terrain Models ◽  
Aerial Vehicle

AbstractAerial thermography is performed from a low−cost aerial vehicle, copter type, for the acquisition of data of medium−size areas, such as neighbourhoods, districts or small villages. Thermographic images are registered in a mosaic subsequently used for the generation of a thermographic digital terrain model (DTM). The thermographic DTM can be used with several purposes, from classification of land uses according to their thermal response to the evaluation of the building prints as a function of their energy performance, land and water management. In the particular case of buildings, apart from their individual evaluation and roof inspection, the availability of thermographic information on a DTM allows for the spatial contextualization of the buildings themselves and the general study of the surrounding area for the detection of global effects such as heat islands.

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