Chicago, IL

Control Surveys, Multibeam Hydrographic Surveys

SEAS was contracted by the USACE Chicago District to provide Multibeam hydrographic surveying & horizontal/vertical control surveys on the Chicago River in downtown Chicago, IL. The survey included:

• Control recovery of existing control marks and establish new marks by GPS campaigns/control network. Verify/establish horizontal & vertical control around the project site.
• Hydrographic condition surveys utilizing Multibeam (MB) on seven miles of the Chicago river.

Control Survey: SEAS personnel observed 1 primary project control and 8 local project control points to verify the positions utilizing Topcon GR5 GNSS receivers (static & RTK). SEAS set 6 control points utilizing GNSS static observations and in areas in downtown Chicago with poor GPS horizons control was set utilizing a Trimble Robotic total station to form a control network. USMARTS were created for all marks.

Hydrographic Surveys: Multibeam was collected utilizing a Reson SeaBat 7125 paired with a Applanix POS MV Wavemaster GNSS/IMU, & ODOM Digibar S for sound velocity profiles aboard a custom 26’ Scully’s Aluminum work boat w/twin Yamaha 200s. Real-time Kinematic (RTK) correction for GPS positioning was used for the survey when in areas that did not have an urban canyon effect (poor GPS horizon created by the tall buildings). SEAS utilized a Trimble robotic total station to track the survey vessel with a 360” prism mounted on top paired with an iXBlue Octans 3000 subsea survey-grade gyrocompass and complete motion sensor in downtown urban canyon areas.

 

Project Challenges:

• 100% coverage & 20% Multibeam data overlap
• Survey area in downtown Chicago with urban canyon effect on GPS
• Integration of positioning from iXBlue Octans 3000, POS GNSS/IMU, & Robotic total station
• Navigation around boat traffic while being tracked by total station
• Snow and freezing rain during survey operations