0000000000594645
AUTHOR
Lauri Mehtätalo
Modeling Forest Tree Data Using Sequential Spatial Point Processes
AbstractThe spatial structure of a forest stand is typically modeled by spatial point process models. Motivated by aerial forest inventories and forest dynamics in general, we propose a sequential spatial approach for modeling forest data. Such an approach is better justified than a static point process model in describing the long-term dependence among the spatial location of trees in a forest and the locations of detected trees in aerial forest inventories. Tree size can be used as a surrogate for the unknown tree age when determining the order in which trees have emerged or are observed on an aerial image. Sequential spatial point processes differ from spatial point processes in that the…
A Model-Based Approach for the Recovery of Forest Attributes Using Airborne Laser Scanning Data
As three-dimensional wall-to-wall information on forest structure, ALS echoes provide information on the growing stock and canopy structure. Even though the ALS echo heights are associated with the dimensions of trees, a theoretical model to relate ALS data with interesting forest attributes is missing. The recorded observation of echo height can be viewed as an outcome of a complex process mixing several random sub-processes related to the forest and the atmosphere in a non-trivial way. The forest-related processes include those generating stand density, tree heights, tree locations, tree crown shapes, and the internal structure of tree crowns. This chapter presents our recent work on deve…
Estimation of forest stand characteristics using individual tree detection, stochastic geometry and a sequential spatial point process model
Airborne Laser Scanning (ALS) results in point-wise measurements of canopy height, which can further be used for Individual Tree Detection (ITD). However, ITD cannot find all trees because small trees can hide below larger tree crowns. Here we discuss methods where the plot totals and means of tree-level characteristics are estimated in such context. The starting point is a previously presented Horvitz–Thompson-like (HT-like) estimator, where the detectability is based on the larger tree crowns and a tuning parameter that models the detection condition. We propose a new method which is based on modeling the spatial pattern of hidden tree locations using a sequential spatial point process mo…
A nonlinear mixed model approach to predict energy expenditure from heart rate.
Abstract Objective. Heart rate (HR) monitoring provides a convenient and inexpensive way to predict energy expenditure (EE) during physical activity. However, there is a lot of variation among individuals in the EE-HR relationship, which should be taken into account in predictions. The objective is to develop a model that allows the prediction of EE based on HR as accurately as possible and allows an improvement of the prediction using calibration measurements from the target individual. Approach. We propose a nonlinear (logistic) mixed model for EE and HR measurements and an approach to calibrate the model for a new person who does not belong to the dataset used to estimate the model. The …