7 research outputs found
ESTIMATION OF TREE POSITION AND STEM DIAMETER USING SIMULTANEOUS LOCALIZATION AND MAPPING WITH DATA FROM A BACKPACK-MOUNTED LASER SCANNER
A system was developed for automatic estimations of tree positions and stem diameters. The sensor trajectory was first estimated
using a positioning system that consists of a low precision inertial measurement unit supported by image matching with data from a
stereo-camera. The initial estimation of the sensor trajectory was then calibrated by adjustments of the sensor pose using the laser
scanner data. Special features suitable for forest environments were used to solve the correspondence and matching problems. Tree
stem diameters were estimated for stem sections using laser data from individual scanner rotations and were then used for calibration
of the sensor pose. A segmentation algorithm was used to associate stem sections to individual tree stems. The stem diameter estimates
of all stem sections associated to the same tree stem were then combined for estimation of stem diameter at breast height (DBH). The
system was validated on four 20 m radius circular plots and manual measured trees were automatically linked to trees detected in laser
data. The DBH could be estimated with a RMSE of 19 mm (6 %) and a bias of 8 mm (3 %). The calibrated sensor trajectory and the
combined use of circle fits from individual scanner rotations made it possible to obtain reliable DBH estimates also with a low precision
positioning system
Long-term trends in PBDEs in sparrowhawk (Accipiter nisus) eggs indicate sustained contamination of UK terrestrial ecosystems
PBDE contamination in terrestrial biota is poorly characterized, and robust data on temporal trends are scarce. We measured temporal (1985â2007) and spatial trends in PBDE contamination in the eggs of the sparrowhawk (Accipiter nisus), a sentinel for the terrestrial environment. Five BDEs were the most abundant (BDE 99
> 47 > 153 > 100 > 154). Their concentrations, and that of the sum PBDEs (ÎŁPBDE), increased from the mid-1980s, peaking in the midlate 1990s at levels that were sustained until the end of the study. This and the predominance of BDE99 contrast with patterns in piscivorous species and suggest sparrowhawks, and perhaps terrestrial species more widely, may be relatively poor metabolizers of penta-BDEs. BDE 196, 197, 201, and 203 concentrations increased linearly through the study, indicating increasing contamination possibly from the presence of these congeners in, and/or debromination of, deca-BDE formulations. Variation in egg ÎŁPBDE concentration was not explained by % urban land cover, human population density or % of arable land in proximity to the nest site, or by land use. Overall, egg ÎŁPBDE concentrations (34â2281 ng/g wet weight) were some of the highest reported in birds from Europe. We found no relationship between ÎŁPBDE concentrations and eggshell thickness