The Ecomapper overview

The Ecomapper is an autonomous underwater vehicle purchased from YSI Inc. It is operated through "Windows Remote desktop" via Wi-fi. GPS is available for localization on water surface and DVL (Doppler Velocity Log) is employed for localization underwater. Our Ecomapper is equipped with Conductivity and Temperature Sensors, Depth Sensor (measure depth from surface), Depth-Sounding sonar (measures height from bottom) and Three-axis digital compass.

We have operated the Ecomapper in two modes

The Ecomapper can be drove manually when it is on surface and within Wi-fi range. In this mode, information about the EcoMapper is displayed on the Underwater Vehicle Console (UVC) but are not recorded by the EcoMapper. The information displayed include the speed, position (Latitude and Logitude), and heading, as well as sensory data that includes temperature, salinity, depth and altitude. • Autonomous mode. In this mode, the Ecomapper follows a predefined course, either on surface or below surface, independently of the user. During missions, the Ecomapper records all sensor measurements into log files. W e can get the following data from the log files after the Ecomapper finishes a mission: Ecomapper positions (latitude and longitude), velocity, pitch angle, roll angle, depth from surface, height to bottom, temperature, sound speed, salinity.

What we have achieved with the Ecomapper

We successfully surveyed the west pond in Georgia Tech Savannah Campus (see Figure 1) autonomously using the Ecomapper. Autonomous missions both on surface and below surface were executed successfully. Bathymetry data were collected during the missions. Figure 2 shows the courses the Ecomapper followed and the bathemetry data collected. By interpolating the raw depth data, we built a bathemetry map for this pond (see Figure 3). The averaged salinity in this pond is around 0.09 ppt (parts per thousand).

As part of the project "Collaborative Research: RAPID: Autonomous Control and Sensing Algorithms for Surveying the Impacts of Oil Spills on Coastal Environments" supported by NSF, the EcoMapper was deployed to survey the retention pond located at the Grand Isle State Park (see Figure 4) in Louisiana . Five autonomous missions between surface and 0.5 meters below surface were executed. We did not let the Ecomapper dive deeper since the pond is shallow, with maximum depth 1.65 meters. The data collected show that the temperature and salinity does not change much with depth (salinity changes<0.5ppt, Temperature changes<1 o C) as the lagoon is shallow. Figure 5 shows the courses the Ecomapper executed and the bathemetry data collected. By interpolating the original depth data, we obtained a bathemetry map for this pond (see Figure 6). The salinity of the lagoon varies between 13ppt and 17 ppt under different weather condition. (see summary)


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