Accuracy of smartphone applications in the field measurements of tree height

Abstract As tree height is one of the important variables measured in forestry, much effort is made to provide its fast, easy and accurate determination. We analysed precision of two widely available smartphone applications (Smart Measure and Measure Height) during the field measurements of tree height. The data was collected in three Scots pine stands in central Poland. We found negative systematic error of both tested applications regardless the distance of the measurement (15 or 20 m). RMSE values of the height estimates varied from 1.01 to 2.46 m depending on the application used and the distance of the measurement. Value of the calculated absolute and relative errors significantly (p < 0.015) positively depended on the actual height of the measured trees and was more diverse for higher trees. Smartphone applications seem to be promising measurement tool for tree height determination, however as for the time being they require improvement before wider introduction into the forest practice.

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Typology of the natural regeneration in a middle-aged Scots pine forest

Silva Gandavensis ◽

10.21825/sg.v53i0.913 ◽

1988 ◽

Vol 53 ◽

Author(s):

C. De Schepper

Keyword(s):

Scots Pine ◽

Natural Regeneration ◽

Free Field ◽

Sandy Soils ◽

Structural Basis ◽

Pedunculate Oak ◽

Pine Stands ◽

Scots Pine Forest ◽

Forest Practice ◽

Scots Pine Stands

The study describes the natural regeneration state of a forest on coarse sandy soils. The natural regeneration was studied in three different ecological conditions: in 30 to 60 year old Scots pine stands, in a 62 year old mixed stand of pedunculate oak and red oak, and on the free field. The analysis of the regeneration groups revealed that the first settler maintained a dominant social position during the following years after the settlement. The structural basis is consequently laid out early. This means that the forest practice has to consider the very first phase of the regeneration as determining for the following evolution of the regeneration groups.

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Measurements of sea-ice flexural stiffness by pressure characteristics of flexural-gravity waves

Annals of Glaciology ◽

10.3189/2013aog64a075 ◽

2013 ◽

Vol 54 (64) ◽

pp. 51-60 ◽

Cited By ~ 9

Author(s):

Aleksey Marchenko ◽

Eugene Morozov ◽

Sergey Muzylev

Keyword(s):

Elastic Modulus ◽

Gravity Waves ◽

Water Depth ◽

Water Pressure ◽

Field Measurements ◽

Effective Elastic Modulus ◽

Flexural Stiffness ◽

Flexural Gravity Waves ◽

Using Data ◽

Relative Errors

Abstract A method to estimate the flexural stiffness and effective elastic modulus of floating ice is described and analysed. The method is based on the analysis of water pressure records at two or three locations below the bottom of floating ice when flexural-gravity waves propagate through the ice. The relative errors in the calculations of the ice flexural stiffness and the water depth are analysed. The method is tested using data from field measurements in Tempelfjorden, Svalbard, where flexural-gravity waves were excited by an icefall at the front of the outflow glacier Tunabreen in February 2011.

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Development and Testing of a New Ground Measurement Tool to Assist in Forest GIS Surveys

Forests ◽

10.3390/f10080643 ◽

2019 ◽

Vol 10 (8) ◽

pp. 643 ◽

Cited By ~ 2

Author(s):

Guangpeng Fan ◽

Feixiang Chen ◽

Yan Li ◽

Binbin Liu ◽

Xu Fan

Keyword(s):

Root Mean Square Error ◽

Mobile Phone ◽

Mean Square Error ◽

Tree Species ◽

Tree Height ◽

Measurement Tool ◽

Mean Square ◽

Height Measurement ◽

Test Dataset ◽

Ground Measurement

In present forest surveys, some problems occur because of the cost and time required when using external tools to acquire tree measurement. Therefore, it is of great importance to develop a new cost-saving and time-saving ground measurement method implemented in a forest geographic information system (GIS) survey. To obtain a better solution, this paper presents the design and implementation of a new ground measurement tool in which mobile devices play a very important role. Based on terrestrial photogrammetry, location-based services (LBS), and computer vision, the tool assists forest GIS surveys in obtaining important forest structure factors such as tree position, diameter at breast height (DBH), tree height, and tree species. This paper selected two plots to verify the accuracy of the ground measurement tool. Experiments show that the root mean square error (RMSE) of the position coordinates of the trees was 0.222 m and 0.229 m, respectively, and the relative root mean square error (rRMSE) was close to 0. The rRMSE of the DBH measurement was 10.17% and 13.38%, and the relative Bias (rBias) of the DBH measurement was −0.88% and −2.41%. The rRMSE of tree height measurement was 6.74% and 6.69%, and the rBias of tree height measurement was −1.69% and −1.27%, which conforms to the forest investigation requirements. In addition, workers usually make visual observations of trees and then combine their personal knowledge or experience to identify tree species, which may lead to the situations when they cannot distinguish tree species due to insufficient knowledge or experience. Based on MobileNets, a lightweight convolutional neural network designed for mobile phone, a model was trained to assist workers in identifying tree species. The dataset was collected from some forest parks in Beijing. The accuracy of the tree species recognition model was 94.02% on a test dataset and 93.21% on a test dataset in the mobile phone. This provides an effective reference for workers to identify tree species and can assist in artificial identification of tree species. Experiments show that this solution using the ground measurement tool saves time and cost for forest resources GIS surveys.

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The use of forest maps for the description of wildlife habitats: limits and recommendations

Canadian Journal of Forest Research ◽

10.1139/x01-038 ◽

2001 ◽

Vol 31 (7) ◽

pp. 1227-1234 ◽

Cited By ~ 32

Author(s):

Christian Dussault ◽

Réhaume Courtois ◽

Jean Huot ◽

Jean-Pierre Ouellet

Keyword(s):

Dominant Species ◽

Basal Area ◽

Tree Height ◽

Field Measurements ◽

Wildlife Habitat ◽

Habitat Characteristics ◽

Tree Age ◽

Habitat Features ◽

Forest Maps ◽

Crown Closure

We evaluated the reliability of forest maps for describing wildlife habitats. During the summer of 1997, we sampled 186 boreal forest stands located in Jacques-Cartier Park, Quebec. In each stand, we measured slope, crown closure, basal area, as well as tree height and age. We determined if map classifications, with regard to dominant species composition, density, tree height, tree age, and slope, correlated with field observations. We also measured lateral cover and deciduous browse availability, variables that are considered useful for the characterization of wildlife habitats, to examine how these habitat features were related to map classification. Age (57% of the sites correctly classified) and density (34%) were the variables for which map classification had the best and worst correspondence with field measurements, respectively. Dominant species on maps were correctly identified in <74, <55, and <40% of the sites in coniferous, mixed, and deciduous stands, respectively. The use of a simple classification method based on cover type alone resulted in improved correlations, since 94, 60, and 29% of the coniferous, mixed, and deciduous stands, respectively, were properly identified on maps. We related lateral cover and food availability to stand categories using the most reliable map variables. We conclude that forest maps are useful for describing major habitats at the stand level. When forest resource maps are to be used for studying habitat suitability, we recommend sampling a subset of stands to assess if important wildlife habitat features, which reflect species requirements, can be related to habitat characteristics as determined by the maps.

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ALGORITHM FOR THE AUTOMATIC ESTIMATION OF AGRICULTURAL TREE GEOMETRIC PARAMETERS USING AIRBORNE LASER SCANNING DATA

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xli-b8-629-2016 ◽

2016 ◽

Vol XLI-B8 ◽

pp. 629-632 ◽

Cited By ~ 1

Author(s):

E. Hadaś ◽

A. Borkowski ◽

J. Estornell

Keyword(s):

Laser Scanning ◽

Tree Height ◽

Field Measurements ◽

Point Clouds ◽

Average Density ◽

Geometric Parameters ◽

Airborne Laser Scanning ◽

Maximum Height ◽

Airborne Laser ◽

Crown Base Height

The estimation of dendrometric parameters has become an important issue for the agricultural planning and management. Since the classical field measurements are time consuming and inefficient, Airborne Laser Scanning (ALS) data can be used for this purpose. Point clouds acquired for orchard areas allow to determine orchard structures and geometric parameters of individual trees. In this research we propose an automatic method that allows to determine geometric parameters of individual olive trees using ALS data. The method is based on the α-shape algorithm applied for normalized point clouds. The algorithm returns polygons representing crown shapes. For points located inside each polygon, we select the maximum height and the minimum height and then we estimate the tree height and the crown base height. We use the first two components of the Principal Component Analysis (PCA) as the estimators for crown diameters. The α-shape algorithm requires to define the radius parameter R. In this study we investigated how sensitive are the results to the radius size, by comparing the results obtained with various settings of the R with reference values of estimated parameters from field measurements. Our study area was the olive orchard located in the Castellon Province, Spain. We used a set of ALS data with an average density of 4 points m<sip>−2. We noticed, that there was a narrow range of the R parameter, from 0.48 m to 0.80 m, for which all trees were detected and for which we obtained a high correlation coefficient (> 0.9) between estimated and measured values. We compared our estimates with field measurements. The RMSE of differences was 0.8 m for the tree height, 0.5 m for the crown base height, 0.6 m and 0.4 m for the longest and shorter crown diameter, respectively. The accuracy obtained with the method is thus sufficient for agricultural applications.

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Simultaneous PIV and DIC Measurements in a Towing Tank Environment with a Flexible Hydrofoil

14th International Symposium on Particle Image Velocimetry ◽

10.18409/ispiv.v1i1.30 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Gunnar Jacobi ◽

Alex Nila

Keyword(s):

Flow Field ◽

Accurate Determination ◽

Measurement Techniques ◽

Weight Ratio ◽

Field Measurements ◽

Tip Vortex ◽

Vortex Center ◽

Phase Lag ◽

Maritime Industry ◽

Wing Tip

Due to their good mechanical properties composite materials are increasingly applied for the construction of lifting surfaces in the maritime industry. However, besides improving the strength to weight ratio of a structure, the anisotropic material properties can also exhibit bend-twist coupling, when exposed to higher loads. In order to experimentally measure the fluid structure interaction, the object of investigation needs to exposed to the same fluid loadings, as it would experience during operation. To investigate the possibility to obtain simultaneous deformation and flow field measurements in a large hydrodynamic testing facility simultaneous PIV and DIC measurements are performed to obtain the deformation of a flexible NACA 0008 hydrofoil and to measure the flow field in the wing tip region. For the assessment of the performance of the methods two scenarios are presented including tests in stationary conditions with constant angles of attack and forced plunging oscillations. The calibration of both measurement systems is done independently and the wing tip, visible in the PIV images, is used for triangulation to find the position of the wing within the PIV coordinate system. The combination of both measurement techniques allows for an accurate determination of tip vortex center positions with respect to the deformed wing and their evolution downstream of the wing. During forced plunging motions, the phase lag of the wing tip and the influence on the wing tip vortex is observed.

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Effects of Photographic Distance on Tree Crown Attributes Calculated Using UrbanCrowns Image Analysis Software

Arboriculture & Urban Forestry ◽

10.48044/jauf.2011.023 ◽

2011 ◽

Vol 37 (4) ◽

pp. 173-179

Author(s):

Mason Patterson ◽

P. Eric Wiseman ◽

Matthew Winn ◽

Sang-mook Lee ◽

Philip Araman

Keyword(s):

Acer Saccharum ◽

Urban Forest ◽

Tree Height ◽

Field Measurements ◽

Tree Crown ◽

Impact Measurement ◽

Basic Field ◽

Trunk Diameter ◽

Crown Volume ◽

Software Utility

UrbanCrowns is a software program developed by the USDA Forest Service that computes crown attributes using a side-view digital photograph and a few basic field measurements. From an operational standpoint, it is not known how well the software performs under varying photographic conditions for trees of diverse size, which could impact measurement reproducibility and therefore software utility. Researchers evaluated the robustness of crown dimension computations made with UrbanCrowns for open-grown sugar maples (Acer saccharum) across a range of sizes from recently transplanted to full maturity. It was found that computations of both crown volume and density were highly repeatable across varying photographic distances. For the majority of tree size classes, crown volume and density varied less than 5% on average over distances ranging from 1.5× to 3.0× tree height; however, crown volume errors of 5%–10% were common for larger trees (>46 cm trunk diameter). UrbanCrowns calculations of crown volume showed strong agreement with calculations derived from equations for geometric solids, both in terms of precision (R2 = 0.9783) and accuracy (B1 = 1.0033). These findings suggest that UrbanCrowns has potential as an objective, reliable method for measuring tree crown attributes that are commonly assessed during urban forest inventories.

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Reliable Estimates of Merchantable Timber Volume from Terrestrial Laser Scanning

Remote Sensing ◽

10.3390/rs13183610 ◽

2021 ◽

Vol 13 (18) ◽

pp. 3610

Author(s):

Dimitrios Panagiotidis ◽

Azadeh Abdollahnejad

Keyword(s):

Laser Scanning ◽

Accurate Determination ◽

Laser Scanner ◽

Terrestrial Laser Scanning ◽

Tree Height ◽

Tree Level ◽

Consensus Method ◽

Field Methods ◽

Forest Inventories ◽

Random Sampling Consensus

Simple and accurate determination of merchantable tree height is needed for accurate estimations of merchantable volume. Conventional field methods of forest inventory can lead to biased estimates of tree height and diameter, especially in complex forest structures. Terrestrial laser scanner (TLS) data can be used to determine merchantable height and diameter at different heights with high accuracy and detail. This study focuses on the use of the random sampling consensus method (RANSAC) for generating the length and diameter of logs to estimate merchantable volume at the tree level using Huber’s formula. For this study, we used two plots; plot A contained deciduous trees and plot B consisted of conifers. Our results demonstrated that the TLS-based outputs for stem modelling using the RANSAC method performed very well with low bias (0.02 for deciduous and 0.01 for conifers) and a high degree of accuracy (97.73% for deciduous and 96.14% for conifers). We also found a high correlation between the proposed method and log length (−0.814 for plot A and −0.698 for plot B), which is an important finding because this information can be used to determine the optimum log properties required for analyzing stem curvature changes at different heights. Furthermore, the results of this study provide insight into the applicability and ergonomics during data collection from forest inventories solely from terrestrial laser scanning, thus reducing the need for field reference data.

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An Improved Tree Height Measurement Technique Tested on Mature Southern Pines

Southern Journal of Applied Forestry ◽

10.1093/sjaf/32.1.38 ◽

2008 ◽

Vol 32 (1) ◽

pp. 38-43 ◽

Cited By ~ 18

Author(s):

Don C. Bragg

Keyword(s):

Tree Height ◽

Real Point ◽

Horizontal Distance ◽

Height Measurement ◽

Similar Triangle ◽

Height Determination ◽

Southern Pines ◽

Crown Shape ◽

Tangent Method ◽

Similar Triangles

Abstract Virtually all techniques for tree height determination follow one of two principles: similar triangles or the tangent method. Most people apply the latter approach, which uses the tangents of the angles to the top and bottom and a true horizontal distance to the subject tree. However, few adjust this method for ground slope, tree lean, crown shape, and crown configuration, making errors commonplace. Given documented discrepancies exceeding 30% with current methods, a reevaluation of height measurement is in order. The sine method is an alternative that measures a real point in the crown. Hence, it is not subject to the same assumptions as the similar triangle and tangent approaches. In addition, the sine method is insensitive to distance from tree or observer position and can not overestimate tree height. The advantages of the sine approach are shown with mature southern pines from Arkansas.

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Magnetopause current as seen by Cluster

Annales Geophysicae ◽

10.5194/angeo-23-901-2005 ◽

2005 ◽

Vol 23 (3) ◽

pp. 901-907 ◽

Cited By ~ 27

Author(s):

M. W. Dunlop ◽

A. Balogh

Keyword(s):

Magnetic Field ◽

Electric Current ◽

Large Scale ◽

Field Component ◽

Accurate Determination ◽

Field Measurements ◽

Magnetic Field Component ◽

Boundary Crossing ◽

Current Layer

Abstract. The four-spacecraft, magnetic field measurements on Cluster can be combined to produce an accurate determination of the electric current in the magnetopause boundary during stable magnetopause crossings. For events that are planar on the scale of the spacecraft configuration, the thickness of the current layer can be accurately estimated from its magnetic profile at each spacecraft and the corresponding boundary crossing times. The latter, give a determination of boundary motion relative to the Cluster array. We use the estimates of all these properties, for a range of spacecraft separation distances, to show, firstly, that the estimate of electric current density is representative even when the spatial scale of the configuration of Cluster spacecraft approaches the thickness of the current layer. Secondly, we show that the estimated current lies in the plane of the boundary and demonstrate this for crossings occurring during large-scale ripples on the magnetopause. Thirdly, we show that the magnitude of the current is accurately represented, averaged over the extent of the current layer, by comparing to the change in the boundary-parallel magnetic field component divided by the estimated current layer thickness. We demonstrate this last point using a range of crossings each having a different thickness and crossing speed, different changes in the magnetic field component and different current densities.

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