Tillé, Yves

2015-9-3, Vallée, Audrey-Anne, Ferland-Raymond, Bastien, Rivest, Louis-Paul, Tillé, Yves

Goals of forest inventories include understanding the forest temporal evolution and monitoring fragile ecosystems. In the province of Quebec, Canada, their implementation faces challenging methodological problems. The survey area covers a large territory which is hardly accessible and has diverse forest. Main operational goals are to spread the sampled plots throughout the survey area and to well represent all forest types in the sample. They are hard to achieve while keeping the costs within budget. Usually, a two dimensional systematic sampling design is applied and the rich auxiliary information is only used at the estimation stage. We show how to use modern and advanced sampling techniques to improve the planning of forest inventories, considering many requirements. For the Quebec forest inventory, we build a two-stage sampling design that has clusters of plots to optimize field work and predetermined sample sizes for forest types. Constraints of spreading the sample in the whole territory and of balancing according to auxiliary variables are also implemented. To meet these requirements, we use unequal inclusion probabilities, balanced sampling, highly stratified balanced sampling, and sample spreading. The impact of these novel techniques on the implementation of requirements and on the precision of survey estimates is investigated using Quebec inventory data.

2015-7-15, Vallée, Audrey-Anne, Ferland-Raymond, Bastien, Rivest, Louis-Paul, Tillé, Yves

In the province of Quebec, Canada, the forest is examined through regular inventories. Requirements for the spreading and the type of trees and for the cost are difficult to manage. We show that modern and advanced sampling techniques can be used to improve the planning of the forest inventories, even if there are many requirements. Our design includes balanced sampling, highly stratified balanced sampling and sample spreading through a two stage sample. The impact of these techniques on the satisfaction of the requirements and on the precision of survey estimates is investigated using field data from a Quebec inventory.

2015-6-15, Vallée, Audrey-Anne, Ferland-Raymond, Bastien, Rivest, Louis-Paul, Tillé, Yves

In the province of Quebec, Canada, the forest is examined through regular inventories. Requirements for the spreading and the type of trees and for the cost are difficult to manage. We show that modern and advanced sampling techniques can be used to improve the planning of the forest inventories, even if there are many requirements. Our design includes balanced sampling, highly stratified balanced sampling and sample spreading through a two stage sample. The impact of these techniques on the satisfaction of the requirements and on the precision of survey estimates is investigated using field data from a Quebec inventory.