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Estimating storm damage with the help of low-altitude photographs and different sampling designs and estimators / Pekka Hyvönen in Silva fennica, vol 52 n° 3 ([01/08/2018])  

Public [article]  inSilva fennica > vol 52 n° 3 [01/08/2018] Titre : Estimating storm damage with the help of low-altitude photographs and different sampling designs and estimators Type de document : Article/Communication Auteurs : Pekka Hyvönen, Auteur ; Jaakko Heinonen, Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] analyse diachronique [Termes IGN] dommage matériel [Termes IGN] estimateur [Termes IGN] Finlande [Termes IGN] forêt [Termes IGN] image aérienne [Termes IGN] inventaire forestier étranger (données) [Termes IGN] modèle de simulation [Termes IGN] plan de vol Mots-clés libres : Théorème central limite Résumé : (Auteur) Climate change has been estimated to increase the risk of storm damage in forests in Finland. There is a growing need for methods to obtain information on the extent and severity of storm damage after a storm occurrence. The first objective of this study was to test whether digital photographs taken from aircrafts flying at low-altitude can be utilized in locating storm-damaged areas and estimating the need for harvesting of wind-thrown trees. The second objective was to test the performance of selected estimators. Depending on distances between flight lines, plots on lines and the used estimator, the relative standard errors of storm area estimates varied between 7.7 and 48.7%. For the area for harvesting and volume of wind-thrown trees, the relative standard errors of estimates varied between 16.8 and 167.3%. Using forest area information from Multisource National Forest Inventory data improved the accuracy of the estimates. However, performance of a simple random sampling estimator and ratio estimator were quite similar. Lindeberg’s method for variance estimation based on adjacent lines was sensitive to line directions in relation to possible trends in storm-damaged area locations. Our results showed that the tested method could be used in estimating storm-damaged area provided that the network of flight lines and photographs on lines are sufficiently dense. The developed model for simulations can be utilized also with forthcoming storms as model’s parameters can be freely adjusted to meet, e.g., the intensity and extent of the storm. Numéro de notice : A2018-508 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE/MATHEMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.14214/sf.7710 Date de publication en ligne : 05/06/2018 En ligne : https://doi.org/10.14214/sf.7710 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91189 [article]

Incorporating tree- and stand-level information on crown base height into multivariate forest management inventories based on airborne laser scanning / Matti Maltamo in Silva fennica, vol 52 n° 3 ([01/08/2018])  

Public [article]  inSilva fennica > vol 52 n° 3 [01/08/2018] Titre : Incorporating tree- and stand-level information on crown base height into multivariate forest management inventories based on airborne laser scanning Type de document : Article/Communication Auteurs : Matti Maltamo, Auteur ; Tomi Karjalainen, Auteur ; Jaakko Repola, Auteur ; Jari Vauhkonen, Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] classification barycentrique [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] hauteur à la base du houppier [Termes IGN] hauteur des arbres [Termes IGN] houppier [Termes IGN] inventaire forestier (techniques et méthodes) [Termes IGN] modèle de simulation [Termes IGN] Pinus (genre) [Termes IGN] placette d'échantillonnage [Termes IGN] régression [Vedettes matières IGN] Inventaire forestier Résumé : (Auteur) This study examines the alternatives to include crown base height (CBH) predictions in operational forest inventories based on airborne laser scanning (ALS) data. We studied 265 field sample plots in a strongly pine-dominated area in northeastern Finland. The CBH prediction alternatives used area-based metrics of sparse ALS data to produce this attribute by means of: 1) Tree-level imputation based on the k-nearest neighbor (k-nn) method and full field-measured tree lists including CBH observations as reference data; 2) Tree-level mixed-effects model (LME) prediction based on tree diameter (DBH) and height and ALS metrics as predictors of the models; 3) Plot-level prediction based on analyzing the computational geometry and topology of the ALS point clouds; and 4) Plot-level regression analysis using average CBH observations of the plots for model fitting. The results showed that all of the methods predicted CBH with an accuracy of 1–1.5 m. The plot-level regression model was the most accurate alternative, although alternatives producing tree-level information may be more interesting for inventories aiming at forest management planning. For this purpose, k-nn approach is promising and it only requires that field measurements of CBH is added to the tree lists used as reference data. Alternatively, the LME-approach produced good results especially in the case of dominant trees. Numéro de notice : A2018-509 Affiliation des auteurs : non IGN Thématique : FORET/MATHEMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.14214/sf.10006 Date de publication en ligne : 27/07/2018 En ligne : https://doi.org/10.14214/sf.10006 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91190 [article]