Forestry and Arboriculture Applications Using High-Resolution Imagery from Unmanned Aerial Vehicles (UAV)

Forests cover over one-third of the planet and provide unmeasurable benefits to the ecosystem. Forest managers have collected and processed countless amounts of data for use in studying, planning, and management of these forests. Data collection has evolved from completely manual operations to the incorporation of technology that has increased the efficiency of data collection and decreased overall costs. Many technological advances have been made that can be incorporated into natural resources disciplines. Laser measuring devices, handheld data collectors and more recently, unmanned aerial vehicles, are just a few items that are playing a major role in the way data is managed and collected. Field hardware has also been aided with new and improved mobile and computer software. Over the course of this study, field technology along with computer advancements have been utilized to aid in forestry and arboricultural applications. Three-dimensional point cloud data that represent tree shape and height were extracted and examined for accuracy. Traditional fieldwork collection (tree height, tree diameter and canopy metrics) was derived from remotely sensed data by using new modeling techniques which will result in time and cost savings. Using high resolution aerial photography, individual tree species are classified to support tree inventory development. Point clouds were used to create digital elevation models (DEM) which can further be used in hydrology analysis, slope, aspect, and hillshades. Digital terrain models (DTM) are in geographic information system (GIS), and along with DEMs, used to create canopy height models (CHM). The results of this study can enhance how the data are utilized and prompt further research and new initiatives that will improve and garner new insight for the use of remotely sensed data in forest management

Prediction of Forest Structural Parameters Using Airborne Full-Waveform LiDAR and Hyperspectral Data in Subtropical Forests

Accurate acquisition of forest structural parameters, which is essential for the parameterization of forest growth models and understanding forest ecosystems, is also crucial for forest inventories and sustainable forest management. In this study, simultaneously acquired airborne full-waveform (FWF) LiDAR and hyperspectral data were used to predict forest structural parameters in subtropical forests of southeast China. The pulse amplitude and waveform shape of airborne FWF LiDAR data were calibrated using a physical process-driven and a voxel-based approach, respectively. Different suites of FWF LiDAR and hyperspectral metrics, i.e., point cloud (derived from LiDAR-waveforms) metrics (DPC), full-waveform (geometric and radiometric features) metrics (FW) and hyperspectral (original reflectance bands, vegetation indices and statistical indices) metrics (HS), were extracted and assessed using correlation analysis and principal component analysis (PCA). The selected metrics of DPC, FW and HS were used to fit regression models individually and in combination to predict diameter at breast height (DBH), Lorey’s mean height (HL), stem number (N), basal area (G), volume (V) and above ground biomass (AGB), and the capability of the predictive models and synergetic effects of metrics were assessed using leave-one-out cross validation. The results showed that: among the metrics selected from three groups divided by the PCA analysis, twelve DPC, eight FW and ten HS were highly correlated with the first and second principal component (r > 0.7); most of the metrics selected from DPC, FW and HS had weak relationships between each other (r < 0.7); the prediction of HL had a relatively higher accuracy (Adjusted-R2 = 0.88, relative RMSE = 10.68%), followed by the prediction of AGB (Adjusted-R2 = 0.84, relative RMSE = 15.14%), and the prediction of V had a relatively lower accuracy (Adjusted-R2 = 0.81, relative RMSE = 16.37%); and the models including only DPC had the capability to predict forest structural parameters with relatively high accuracies (Adjusted-R2 = 0.52⁻0.81, relative RMSE = 15.70⁻40.87%) whereas the usage of DPC and FW resulted in higher accuracies (Adjusted-R2 = 0.62⁻0.87, relative RMSE = 11.01⁻31.30%). Moreover, the integration of DPC, FW and HS can further improve the accuracies of forest structural parameters prediction (Adjusted-R2 = 0.68⁻0.88, relative RMSE = 10.68⁻28.67%)

Aplicación de imágenes de satélites y datos LiDAR en la modelización e inventario de Eucalyptus spp en Uruguay

La integración de información de inventarios de campo, con datos procedentes de sensores remotos y su alta correlación con la estructura de la vegetación, permite ajustar modelos precisos para la estimación de la producción forestal. Esto impacta reduciendo costos, tiempos y sesgos, generando productos que son insumos para procesos como la segmentación y la optimización de la cosecha. En este trabajo se presenta una alternativa a los inventarios forestales y al procesamiento de datos, mediante el uso de sensores LiDAR e imágenes multiespectrales. El objetivo general fue evaluar el uso de LiDAR y datos multiespectrales, en plantaciones de Eucalyptus grandis y Eucalyptus dunnii en Uruguay; para mejorar la calidad y la cantidad de información brindada para optimizar los procesos de gestión forestal con respecto a los sistemas de inventario tradicionales. Los resultados obtenidos demuestran la mejora en la precisión y en la calidad de los datos frente a los inventarios tradicionales. Se proporcionan herramientas que permiten mejorar la precisión en cuatro aspectos para la cuantificación y el manejo de la producción forestal: i) el uso de modelos compatibles y aditivos; ii) el modelado de las variables del rodal a gran escala empleando datos de teledetección; iii) la delimitación de zonas homogéneas dentro del rodal basada en una evaluación no supervisada; y iv) un método de programación lineal que optimiza los planes de corta basado en la disponibilidad de madera, el secuestro de carbono y el Valor Actual Neto. Se concluye que la aplicación de herramientas de geomática en el sector forestal supone un cambio fundamental en las prácticas de inventarios, desde su planificación, ejecución y resolución, así como de la capacidad para generar modelos predictivos y de algoritmos de segmentación con mayor precisión. Se comprobó que el uso de datos procedentes de sensores activos y pasivos incrementa las posibilidades de automatización de inventarios forestales, aumentando la resolución espacial y la temporal de la cartografía forestal. Esto, junto con el uso de técnicas estadísticas paramétricas y no paramétricas, constituyen un avance en el campo del manejo forestal en Uruguay.The integration of information from field inventories, with data from remote sensors, and its high correlation with the structure of the vegetation, allows to adjust precise models for the estimation of forest production. This allows for a reduction in costs, time and bias, producing valuable inputs for processes such as segmentation and optimizing the harvest. Here we present an alternative to forest inventories and data processing through the use of LiDAR and multispectral images. The main objective was to evaluate the use of LiDAR information and high-resolution multispectral data in Eucalyptus plantations in Uruguay, to improve the quality and quantity of information provided to optimize forest management processes with respect to traditional inventory systems. The results obtained demonstrate the improvement in precision and quality of the data compared to traditional inventories. Tools that improve precision in four fundamental aspects for the quantification and management of forest production are provided: i) the use of compatible and additives models; ii) modeling of stand variables on a large scale using remote sensing data; iii) delimitation of homogeneous areas within the stand based on an unsupervised assessment; and iv) a method for optimizing felling plans based on timber availability, carbon prices, and harvest age. The main conclusion is that the application of geomatic tools in the forestry sector represent a fundamental change in inventory practices, from planning, execution and resolution, as well as the ability to generate predictive models and segmentation algorithms with greater precision than those obtained with field inventories. Throughout the thesis, it is shown that the use of data from different active and passive sensors increases the possibilities for automating forest inventories, increasing the spatial and temporal resolution of forest cartography. This, together with the use of parametric and non-parametric statistical techniques, constitutes an advance in the field of forest management in Uruguay