INS options include the Kearfott T24, the Kearfott T16 and the IxBlue ROVINS-154. These are navigation-quality INS systems which provide very accurate short-term navigation and motion sensing. They are integrated with a DVL (and GPS when surfaced) to provide a highly accurate AUV navigation solution. With the T24 INS and 600kHz DVL the navigation accuracy for the AUV going in a straight line is better than 5.5m in 6km (1hr submerged), or ~25m for the T16 (same conditions). ROVINS-154 accuracy figures are available on enquiry. The navigation accuracy is improved when running a lawnmower survey pattern, resulting in about 2m/hour navigation drift rate for the T24/600kHzDVL (conditions and survey pattern dependent).
The RD Instruments Explorer DVL is a small, low power consuming DVL designed especially for small platforms operating in the littoral zone. Typically the 600kHz DVL will be used, for maximum accuracy (other frequency options are available). The board design of the DVL allows it to be tightly mechanically coupled with the Inertial Navigation System (INS) in a compact package that is mounted in one Gavia module.
In the DVL the water current is calculated as the difference between the measured bottom track velocity and the measured water velocity rotated into an Earth-fixed reference frame using the vehicle’s best orientation estimate. The water current is logged on a solid state flash disk in the Control and Communication Module for post-mission analysis.
Using the altimetry provided by the DVL, the Gavia Depth Pilot is able to maintain a set altitude above the bottom for the purpose of performing side-scan or photographic surveys. While tracking the bottom the vehicle observes the operating constraints of the minimum and maximum depth specified in the mission plan. The Gavia will not descend beyond the specified maximum depth, but rather continue at this depth until the bottom rises above this depth. If the vehicle is unable to stay within the specified minimum depth while maintaining constant altitude, the vehicle will proceed onto the next leg of its predefined survey pattern.
- Kearfott T24 or T16B INS or IXSEA ROVINS – 154 INS
- Teledyne RD Instruments DVL