Department of Statistics Seminar
North Carolina State University

presents

Dr. Pamela Abbitt

North Carolina State University

"A Hierarchical Model for Soil Profile Data"

ABSTRACT

The National Cooperative Soil Survey (NCSS) program is charged with constructing county soil survey reports which contain soil maps and descriptions of all soils found within each county in the United States. Like most soil mapping projects, NCSS relies on field-collected core samples. On a given core sample, many characteristics (horizon type, pH, etc.) are recorded for each horizon of soil, and these horizon-specific observations make up an observed profile (horizon profile, pH profile, etc.) . We propose hierarchical models for profile data. Soil horizon profiles are modeled as categorical stochastic processes indexed by depth. The probability of occurrence of each category is the product of a factor which models the horizon thickness and a factor which models the horizon type. Profiles of other soil characteristics can be modeled conditional on the horizon profile. The posterior distribution of unknown model parameters is numerically approximated using MCMC techniques. The hierarchical model provides a comprehensive framework for estimation objectives, and can handle many soil characteristics of interest.

Friday, February 25, 2000

3:35 - 4:35 pm

206 Cox Hall

Refreshments will be served on the second floor of Dabney Hall (left of Room 222) at 3:00 pm.