Discover the new Gaps M5 and learn how to choose the USBL best suited for your need

Gaps M5 is the latest addition to iXblue’s USBL product range, which includes the renown Gaps (now renamed Gaps M7). With over 300 units operating worldwide, Gaps high-accuracy USBL system has become a reference for many users across the world, from diver tracking, workclass ROV surveys, and AUV shallow water missions, to the dynamic positioning DP3 of 100-meter long vessels. To address the needs of our customers for accuracy and performance for less constraining jobs, iXblue has extended its USBL Series, with Gaps M5. a compact, export-free, cost-effective and omnidirectional USBL system.

In this article, you will learn all about the new Gaps M5 and how it compares with Gaps M7, so that you can determine which systems is best suited for your need.



Gaps M5 is an omnidirectional USBL acoustic positioning systems that does not require any on-the-field calibration. Indeed it embeds a motion sensor in its housing: a free-of-export Octans Nano AHRS based on iXblue FOG technology for stable heading roll and pitch compensation and a true north reference.

Smaller and lighter, the new Gaps M5 is easy to install and ready-to-use and. It is suitable for vertical and horizontal tracking of subsea assets for ultra-shallow water to medium water depths and offers an accuracy better than 0.5% of the slant range up to 995m, In practice, this means that, when positioning a vessel at a 500m distance, Gaps M5 is accurate to a maximum of 2,5m. The maximum operating range is achievable even in extremely noisy conditions. Another big benefit of Gaps M5 is that it is export-free and allows hassle-free shipment and operations.



Gaps M5 has kept the M7 unique design, but with shorter legs and an overall height reduced by about 12 cm. The 3D 4-hydrophone antenna still has different legs lengths to enhance horizontal tracking capabilities and the acoustic still offers maximum aperture and allows up to 200° omnidirectional coverage without needing to tilt the antenna.  This is extremely efficient in shallow water and horizontal tracking conditions especially when multiple vehicles must be simultaneously located at 360°.


Gaps M7 and M5 in Brest factory in February 2020 (Gaps will now be marked as Gaps M7)
Gaps M5 200° aperture



Gaps M5 is especially suited for subsea positioning needs of 1.000m or less,  for any tracking operation, from diver- to multiple subsea assets- or inspection ROV- tracking, while Gaps M7 remains the best asset for highest survey requirements, subsea multibeam and laser scan positioning (as it offers an accuracy that can reach 0.6% of the slant range up to 4000m).

For reservoir dam IMR operations, where a ROV must be positioned below a distance of 100m with sub-metric accuracy, Gaps M5 will  be the best solution. Overall Gaps M5 will be the preferred solution for all short distance applications such as rivers, lakes and dam environments. Thanks to its compact size and embedded AHRS, it is easy to integrate and operate and can be used on small vessels with reduced crew onboard or even deployed on instrumented buoys.

The above are examples of use of Gap M5 and Gap M7 – but we also recommend talking to our iXblue experts to help you determine the best solution suited for your operation.


More detailed info about the Gaps M5 and  Gaps M7.