This diagram explains how EXACT uses a technology known as JASON closed-loop microbathymetry to make detailed maps of underwater sites. 1. EXACT transponders are placed around site and their positions precisely calibrated 2. EXACT transponders listen for coded "ping" from JASON, respond with coded ping 3. Travel times of acoustic signal are used to triangulate JASON position, accurate to ~1 cm 3three times per second 4. Position data is fed-back into control system; under automatic (closed-loop) control, JASON runs straight tracklines over wreck site at slow speed (0.1 meters/sec) 5. Sonar beam on vehicle scans across wreck site and records precise altitude information. Data is then combined with vehicle positioning and attitude to produce microbathymetry plot of site 6. Digital still photos are taken simultaneously for mosaic Image / MIT DeepArch Research Group
