Hydrographic Surveying
  Howard Hanson Dam | Brantley Reservoir | Ute Reservoir

Static GPS survey techniques were used to establish a control network for this project, which covered a total of 21 square miles. A total of four and one half square miles were mapped using RTK GPS integrated with a fathometer to complete the bathymetric portion of the survey. The terrestrial mapping for the survey was obtained by the placement of panel points in conjunction with aerial photos. A total of 21,000 GPS points were used to determine underwater topography while 63 panel points were processed through analytic aerotriangulation to determine topography of the land. This project was performed during adverse weather conditions, which included high winds and two to three-foot waves. After integrating information from the aerial and bathymetric surveys, Tetra Tech discovered an inconsistency in the vertical datums used by the client. This resolved a large discrepancy in area capacity calculations regarding this reservoir for the client.