Color coded bathmetry map of Cape Canaveral, Florida, derived from boat based sounding data (2014)

The GPS antenna and receiver acquisition configuration used at the reference station was duplicated on the survey vessel (rover). The base receiver and the rover receiver record their positions concurrently at 10Hz recording intervals throughout the survey. All processed measurements are referenced to the base station coordinates. NOAA/NGS CORS stations CCV6 and a new ground-control point or benchmark within the study area were used as reference receiver sites. For this survey, one new benchmark was built using standard benchmarks procedures. GPS base stations were operated within approximately 15 to 20 km of the survey area. New benchmarks positions were surveyed using Ashtech Z-Extreme, 12 channel dual-frequency GPS receivers. Full-phase carrier data were recorded on each occupied benchmark in Ashtech proprietary BIN format with daily occupations ranging from 6 to 12 hours. BIN files were then converted to RINEX-2 format for position processing. For newly established benchmarks, all static base station GPS sessions were submitted for processing to the NOAA/NGS OPUS software. The base location results from OPUS were entered into a spreadsheet to compute one final positional coordinate and error analysis for that base location. The final positional coordinate (latitude, longitude, and ellipsoid height) is the weighted average of all GPS sessions. For each GPS session, the weighted average was calculated using the OPUS result and the total session time in seconds; therefore, longer GPS occupation times held more value than shorter occupation times. OPUS results are computed relative to IGS08 coordinate system. The established geodetic reference frame for the project was WGS84. Therefore, final reference coordinates used to process the rover data were transformed from IGS08 to WGS84 using National Oceanic and Atmospheric Administration/National Geodetic Survey (NOAA/NGS) Horizontal Time-Dependent Positioning HTDP software v3.2.3. OPUS results provide an error measurement for each daily solution. Applying these error measurements, the horizontal accuracy of the base station is estimated to be 0.02 m root mean squared (RMS). The kinematic (rover) trajectories were processed using GrafNav v8.50 software by Novatel, Inc. A horizontal error measurement, RMS is computed for each epoch. The horizontal trajectory errors varied between 0 and 0.06 m. During acquisition, boat motion was measured using a TSS DMS-05 heave, roll, and pitch sensor, which can measure within 0.05 degrees. The TSS data string was captured and recorded in the HYPACK RAW bathymetry data files. Using USGS Transect Viewer software, the differentially corrected navigation files exported from GrafNav were parsed together by time with the HYPACK RAW files and then merged together, at which time the TSS measurements were used to geometrically correct the soundings at each differentially corrected position. The uncertainties of the roll and pitch corrections applied to the horizontal position are unknown. The combined horizontal error from base station coordinate solutions and rover trajectories ranged from 0.02 and 0.08 m, with an average of approximately 0.04 m.