GPS Buoy Campaigns for Vertical Datum Improvement and Radar Altimeter Calibration
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Date
2004-01
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Ohio State University. Division of Geodetic Science
Abstract
This report summarized three Global Positioning System (GPS) buoy campaigns in the
Great Lakes from 1999 to 2003 that were carried out by the Laboratory of Space Geodesy and
Remote Sensing Research in the Department of Civil and Environmental Engineering and
Geodetic Science (CEEGS), at the Ohio State University. The report focuses on the field
work procedure of GPS buoy operation in these past campaigns and is intended to provide
experience for similar applications in the future.
The campaigns in this report include the Holland Campaign in Lake Michigan in 1999,
the Marblehead Campaign in Lake Erie in 2001, and the Cleveland Campaign in Lake Erie in
2003. The major objective of these campaigns is to establish a calibration site for multiple
satellite altimeters by using the GPS buoy to and the existing tide gauges provided by the
Center for Operational Oceanographic Products and Services (CO-OPS) in the National
Oceanic and Atmospheric Administration (NOAA). The campaigns provide useful information
to the applications including radar altimeter absolute calibration, the establishment of the safe
navigation in the Great Lakes, and the development of an integrated shoreline information in a
spatial information database for coastal management and decision making. Since the report
focuses primarily on the field work procedure, only limited results are presented. The published
calibration results using the data from these campaigns are cited in this report.
Generally, the GPS buoy is defined by putting GPS equipments on a floating object,
which includes different types of buoys and could even be a moving vessel. The use of GPS
buoys is a relatively new technique for the marine applications and its designs and operations
vary from one application to another. For example, its platform could range from a small lifesaver
type to an autonomous ruggedized type buoy. However only the OSU waverider GPS
buoy, a life-saver type buoy that was used in these campaigns, is stressed in this report.
The OSU waverider GPS buoy is a fairly simple design: it is built by attaching a
Dorne/Margolin Element with Choke Ring antenna on top of a 2- feet (diameter) life-saver buoy
covered with a transparent radome. The buoy is tethered to a boat where the receiver, power
supply and the operators reside. Marks are made on four sides of buoy and their offsets to the
antenna reference point (ARP) are carefully measured in the laboratory. The operator needs
to observe the water surface with respect to these marks in order to accurately refer ARP to the
water surface. The buoy data is post-processed with differential GPS (DGPS) in kinematic
mode after the field work.
The campaign-related documents, including National Geodetic Survey (NGS) data
sheets, GPS Station Observation Log, Visibility Obstruction Diagram, campaign proposal, and
field work log, are attached in the Appendices.
Description
The report was prepared by Kai-chien Cheng, a graduate research associate in the
Laboratory for Space Geodesy and Remote Sensing, at the Ohio State University, under the
supervision of Professor C. K. Shum. This report was supported by the National Oceanographic
Partnership Program Grant (Dynalysis of Princeton #865618), National Aeronautics and Space
Administration TOPEX/POSEIDON Extended Mission Grant (NAG 5-6910/JPL961462),
National Aeronautics and Space Administration Earth Science Information Partnership CAN
Grant (CIT #12024478), National Aeronautics and Space Administration Interdisplanary
Science Project (NAG5-9335), National Science Foundation Digital Government Grant (EIA-
0091494, and the Ohio Sea Grant Program (R/CE-5).