Mounting an Auxiliary GPS
The DVL will support an on-ROV GPS. Cerulean offers a GPS option that is packaged for 300m depths and has a penetrator and connector for the DVL electronics. You can supply your own GPS as well. Cerulean does not offer integration support for other GPS units, although anything that looks electrically and protocol-wise like an Adafruit Ultimate GPS should work with no problems. If using DVL power the GPS can draw a maximum of 20 mA at 3.3V. Serial parameters are 9600 baud, 8 data bits, 1 stop bit, no parity.
The GPS antenna needs to be placed where it will be out of the water when the ROV is surfaced. Water is a highly effective GPS signal block and even 5mm of water over the antenna will seriously disrupt reception.
Bitter experience tells us that things sticking up on top of an ROV get broken off when handling or transporting the ROV. The Cerulean GPS is designed to have a low non-snag profile and to ward off accidental blows. It mounts to the frame of a Blue ROV as shown in the figures below. Be sure your ROV is ballasted and balanced to keep the GPS out of the water when on the surface.
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