Bathymetry: Estimation of Coastal Water Depths and Expression of Unceqrtainty Using the NIST Standardized Approach
Courtney Sykes
Master's Candidate
Department of Statistics
Colorado State University
Friday, April 28, 2006
3:10 p.m.
E106 Engineering Building


Bathymetry is the “science of measuring water depths (usually in the ocean) in order to determine bottom topography”. Bathymetric data for areas of Maryland's Chesapeake Bay are obtained by a research vessel using a sonar sounder. The vessel surveys the designated site via transects. During the course of the survey process, the tide changes thereby affecting the depth estimates. A depth recorder submerged near the survey site monitors the change in tide. This depth recorder data will be used to remove the tidal effect from the bathymetric data. Like elevation, bathymetric data needs to be measured relative to a benchmark. For elevation, the standard benchmark is sea level. For bathymetric data, the standard is Mean Lower Low Water (MLLW). The Chesapeake Bay has two low tides and two high tides each day. The lower of the two low tides is called the lower low water (LLW) while the higher of the two low tides is called the higher low water (HLW) . MLLW is the average height of the daily lower low waters (LLW) over a 19 year period. MLLW is only known for tidal stations administered by the National Oceanic & Atmospheric Administration (NOAA). The tidal data relative to MLLW at the closest NOAA tidal station will be used to adjust the bathymetric data at the survey site such that, it too, is relative to MLLW. An attempt is made to identify all sources of bias and error in the measurement process. The resulting measurement biases and errors will be expressed using NIST standards outlined in “Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results” by Barry N. Taylor and Chris E. Kuyatt. The NIST standards are compliant with the International Organization for Standardization's Guide to the Expression of Uncertainty in Measurement (ISO GUM). A brief synopsis of the NIST guidelines will be given.



  home for studentspeoplecoursesdistance degreeresearchconsulting seminars resources
PRIMESSTARMAPemail us equal opportunitydisclaimerweb master • last modified: August 11 2003