Browsing by Subject "forest mensuration"

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  • Luoma, Ville; Saarinen, Ninni; Wulder, Michael A.; White, Joanne C.; Vastaranta, Mikko; Holopainen, Markus; Hyyppä, Juha (2017)
    Forest resource information has a hierarchical structure: individual tree attributes are summed at the plot level and then in turn, plot-level estimates are used to derive stand or large-area estimates of forest resources. Due to this hierarchy, it is imperative that individual tree attributes are measured with accuracy and precision. With the widespread use of different measurement tools, it is also important to understand the expected degree of precision associated with these measurements. The most prevalent tree attributes measured in the field are tree species, stem diameter-at-breast-height (dbh), and tree height. For dbh and height, the most commonly used measuring devices are calipers and clinometers, respectively. The aim of our study was to characterize the precision of individual tree dbh and height measurements in boreal forest conditions when using calipers and clinometers. The data consisted of 319 sample trees at a study area in Evo, southern Finland. The sample trees were measured independently by four trained mensurationists. The standard deviation in tree dbh and height measurements was 0.3 cm (1.5%) and 0.5 m (2.9%), respectively. Precision was also assessed by tree species and tree size classes; however, there were no statistically significant differences between the mensurationists for dbh or height measurements. Our study offers insights into the expected precision of tree dbh and height as measured with the most commonly used devices. These results are important when using sample plot data in forest inventory applications, especially now, at a time when new tree attribute measurement techniques based on remote sensing are being developed and compared to the conventional caliper and clinometer measurements.
  • Nyyssönen, Aarne (Suomen metsätieteellinen seura, 1979)
  • Mozgeris, Gintautas (The Finnish Society of Forest Science and The Finnish Forest Research Institute, 1996)
    This paper deals with the testing of dynamic stratification for estimating stand level forest characteristics (basal area, mean diameter, mean height and mean age) for a 117 ha study area in Finland. The results do not show possibilities to achieve more accurate estimates using only Landsat TM principal components as auxiliary data opposed to static stratification. It was found that in dynamic stratification non-measured observations should be assigned the mean characteristics of the measured observations that belong to the same cube (class) instead of randomly selected ones. Stratification errors tend to decrease with the lessening of stratification variable classes until a certain limit. If only one principal component is used the number of classes has however little influence. Low field values are overestimated and high values underestimated. The only successful results were obtained using two variables of different origin – the qualitative development stage class and the quantitative 1st principal compund. The lowest root mean square error in estimating basal area was 6.40 m2/ha, mean diameter 3.34 cm, mean height 2.65 m and mean age 14.06 years. This increase of stratification accuracy is mainly resulted by the use of development stage class as an auxiliary variable.
  • Junttila, Oula Samuli; Vastaranta, Mikko Antero; Hämäläinen, Jarno; Latva-käyrä, Petri; Holopainen, Markus Edvard; Hernandez-Clemente, Rocio; Hyyppä, Hannu; Navarro-Cerrillo, Rafael (2017)
    The effect of forest structure and health on the relative surface temperature captured by airborne thermal imagery was investigated in Norway Spruce-dominated stands in Southern Finland. Airborne thermal imagery, airborne scanning light detection and ranging (LiDAR) data and 92 field-measured sample plots were acquired at the area of interest. The surface temperature correlated most negatively with the logarithm of stem volume, Lorey’s height and the logarithm of basal area at a resolution of 254 m2 (9-m radius). LiDAR-derived metrics: the standard deviations of the canopy heights, canopy height (upper percentiles and maximum height) and canopy cover percentage were most strongly negatively correlated with the surface temperature. Although forest structure has an effect on the detected surface temperature, higher temperatures were detected in severely defoliated canopies and the difference was statistically significant. We also found that the surface temperature differences between the segmented canopy and the entire plot were greater in the defoliated plots, indicating that thermal images may also provide some additional information for classifying forests health status. Based on our results, the effects of forest structure on the surface temperature captured by airborne thermal imagery should be taken into account when developing forest health mapping applications using thermal imagery.
  • Nyyssönen, Aarne; Kilkki, Pekka (Suomen metsätieteellinen seura, 1966)
  • Tanhuanpää, Topi; Saarinen, Ninni; Kankare, Ville; Nurminen, Kimmo; Vastaranta, Mikko; Honkavaara, Eija; Karjalainen, Mika; Yu, Xiaowei; Holopainen, Markus; Hyyppä, Juha (2016)
    Height models based on high-altitude aerial images provide a low-cost means of generating detailed 3D models of the forest canopy. In this study, the performance of these height models in the detection of individual trees was evaluated in a commercially managed boreal forest. Airborne digital stereo imagery (DSI) was captured from a flight altitude of 5 km with a ground sample distance of 50 cm and corresponds to regular national topographic airborne data capture programs operated in many countries. Tree tops were detected from smoothed canopy height models (CHM) using watershed segmentation. The relative amount of detected trees varied between 26% and 140%, and the RMSE of plot-level arithmetic mean height between 2.2 m and 3.1 m. Both the dominant tree species and the filter used for smoothing affected the results. Even though the spatial resolution of DSI-based CHM was sufficient, detecting individual trees from the data proved to be demanding because of the shading effect of the dominant trees and the limited amount of data from lower canopy levels and near the ground.
  • Nyyssönen, Aarne (Suomen metsätieteellinen seura, 1959)
  • Kuusela, Kullervo (Suomen metsätieteellinen seura, 1964)
  • Kuusela, Kullervo; Kilkki, Pekka (Suomen metsätieteellinen seura, 1963)
  • Nyyssönen, Aarne; Kilkki, Pekka; Mikkola, Erkki (Suomen metsätieteellinen seura, 1967)
  • Kilkki, Pekka (Suomen metsätieteellinen seura, 1979)
  • Kilkki, Pekka (Suomen metsätieteellinen seura, 1983)
  • Nyyssönen, Aarne; Kilkki, Pekka (Suomen metsätieteellinen seura, 1965)
  • Nyyssönen, Aarne; Roiko-Jokela, Pentti; Kilkki, Pekka (Suomen metsätieteellinen seura, 1971)
  • Wilde, S. A. (Suomen metsätieteellinen seura, 1965)
  • Saarinen, Ninni Pauliina; Vastaranta, Mikko Antero; Näsi, Roope; Rosnell, Tomi; Hakala, Teemu; Honkavaara, Eija; Wulder, Michael A.; Luoma, Ville Valtteri; Tommaselli, Antonio; Imai, Nilton; Werneck, Eduardo; Guimaraes, Raul; Holopainen, Markus Edvard; Hyyppä, Juha (2017)
  • Kuusela, Kullervo (Suomen metsätieteellinen seura, 1960)