iXBlue Gaps Series Instruction Manual

..................................................................................................................... 1
1QUESTIONS CONCERNING BOTH GAPS SYSTEMS .............................................. 5
1.1 WHY IS A GAPS CALIBRATION FREE? ...........................................................................................5
1.2 IF GAPS SYSTEMS ARE CALIBRATION FREE,WHY DO INEED TO EXECUTE AN ALIGNMENT
PROCEDURE?........................................................................................................................................5
1.3 HOW CAN IRETRIEVE THE IP ADDRESS OF MY GAPS SYSTEM?......................................................5
1.4 HOW SHOULD ISET THE BLANKING TIME ON MY GAPS FOR THE BEST PERFORMANCE? ...................5
1.5 WHAT IS THE RECOMMENDED PROCEDURE FOR HYDROPHONE AND TRANSDUCER MAINTENANCE?..6
1.6 HOW DO ICHECK THE BATTERY STATUS OF MY MT9?...................................................................6
1.7 WHAT SHOULD BE THE MAXIMUM VOLTAGE WHEN MY MT9 BEACON IS FULLY CHARGED?...............6
1.8 WHAT IS THE MINIMUM VOLTAGE FOR AN MT9 BEACON TO BE OPERATIONAL?...............................7
1.9 HOW SHOULD ICONFIGURE MY MT9 INTERROGATION CODES FOR RESPONDER MODE? ..................7
1.10 WHAT IS GAPS SYSTEMS POSITIONING ACCURACY?......................................................................7
1.11 WHAT ARE GAPS M7 AND GAPS M5 MAXIMUM RANGE?................................................................7
1.12 HOW ACCURATE MUST MY GPS LEVER ARM BE?..........................................................................8
1.13 WHAT IS THE LONGEST AVAILABLE CABLE FOR GAPS SYSTEMS? ..................................................8
1.14 WHERE IS THE REFERENCE POINT OF THE GAPS SYSTEMS? ..........................................................8
1.15 WHY ARE GAPS SYSTEMS THE MOST ADAPTED FOR SHALLOW WATER?.........................................8
1.16 WHICH NAVIGATION SOFTWARES ARE COMPATIBLE WITH GAPS M7 AND M5?...............................8
1.17 DO INEED TO MEASURE THE SOUND VELOCITY PROFILE?..............................................................9
1.18HOW TO OPTIMIZE GAPS M7 AND M5 PERFORMANCES? ...............................................................9
1.19 WHAT TO DO IF POSITIONING ACCURACY IS NOT AS GOOD AS EXPECTED?......................................9
1.20 WHAT COMES IN A STANDARD GAPS M7/M5 DELIVERY?...............................................................9
1.21 WHAT OPERATING SYSTEM DO GAPS M7/M5 SUPPORT ?..............................................................9
1.22 WHAT IS THE BEST LOCATION TO MOUNT THE GAPS M7/M5 HEAD?.............................................10
1.23 WHAT IS THE BEST LOCATION TO MOUNT THE BEACON ON ROV?................................................10
1.24 WHAT IS THE IMPACT OF GAPS M7/M5 MOUNTING MISALIGNMENTS (HEADING,ROLL,PITCH)?......10
1.25 DO THIRD-PARTY BEACONS HAVE THE SAME POSITIONING PERFORMANCES COMPARED TO IXBLUE
BEACONS?..........................................................................................................................................10
2QUESTIONS CONCERNING GAPS M5 ................................................................... 11
2.1 PERFORMANCE,OPERATION AND APPLICATIONS.........................................................................11
A.1.1 HOW MANY TARGETS CAN ITRACK WITH GAPS M5 ............................................... 11
A.1.2 IN RESPONDER MODE,HOW MANY BEACONS CAN BE TRIGGED SIMULTANEOUSLY WITH
THE SURFACE UNIT SYNCH OUTPUT?.................................................................................. 11
A.1.3 DOES GAPS M5 SUPPORT DATA TELEMETRY?...................................................... 11
A.1.4 WHAT IS THE MAXIMUM DATA RATE OBTAINED IN COMMUNICATION MODE?............. 11
A.1.5 CAN WE USE THE SYSTEM FOR POSITIONING AND COMMUNICATION IN PARALLEL?.. 11

A.1.6 IN CASE OF UNAVAILABILITY OF GPS SIGNAL,IS THERE A WORKAROUND TO BYPASS
THE INPUT OF GPS SIGNAL WHEN TESTING WITHOUT INDUCING A SYSTEM ERROR MESSAGE?11
A.1.7 IS GAPS M5 BETTER THAN GAPS M7 FOR SOME APPLICATIONS?...........................11
A.1.8 WHAT IS THE TELEMETRY RATE?..........................................................................12
A.1.9 WHAT IS THE RECOMMENDED SHORT RANGE OF OPERATION?................................12
A.1.10 CAN THE RANGE BE EXTENDED BEYOND 995?...................................................12
A.1.11 IS THERE ANY DECREASE IN POSITION AROUND THE HORIZONTAL BEAMS (180-200
DEGREES)? CAN THE GAPS BE TILTED IN SHALLOW WATER TO HAVE BETTER POSITION
PERFORMANCE OR IS THIS NOT NEEDED AT ALL? ................................................................12
A.1.12 WHAT IS THE POSITION UPDATE RATE? .............................................................12
A.1.13 YOU SAY THERE IS NO CALIBRATION NEEDED AT ALL?NOT EVEN A SPINCHECK?
YOUR COMPETITOR STATES THAT WITH AN INTEGRATED INS, A SPINCHECK IS STILL NEEDED.12
A.1.14 CAN ONE LOAD NEW CALIBRATION PARAMETERS?.............................................12
A.1.15 HOW ABOUT THE CALIBRATION INTERVAL FOR THE OCTANS NANO GYRO?DO WE
NEED TO CALIBRATE THE GYRO? .......................................................................................13
A.1.16 SINCE GAPS M5 IS PRE-CALIBRATED AT FACTORY AND NO CALIBRATION IS NEEDED,
WHAT CAN WE DO IF WE FIND OUT THAT THE UNDERWATER POSITION IS NOT GOOD OR FAR
AWAY FROM THE ACTUAL POSITION?..................................................................................13
A.1.17 IF POSITION IS UNSTABLE IN VERY SHALLOW WATERS –WHAT WILL BE THE
DIFFERENCE PERFORMANCE-WISE BETWEEN GAPS M5 AND M7?........................................13
A.1.18 CAN GAPS M5 BE UTILIZED AS DP SYSTEM REFERENCE SYSTEMS? ..................13
A.1.19 IS GAPS M5 STABLE ON VESSEL MOVE? ...........................................................13
A.1.20 WHAT IS THE MAXIMUM SEA STATE THAT WE CAN USE GAPS M5? ......................13
A.1.21 HOW DOES THE GAPS INTERFACE WITH YOUR INS ON AN AUV? ........................14
A.1.22 HOW FAST CAN AUV BE TRACKED RELIABLY? ..................................................14
A.1.23 HOW CAN IUSE THE M5 TO COMMUNICATE WITH AN AUV IN MODEM MODE ON A
COMPATIBLE BEACON WITHOUT USING THE TOWFISH MODEM FOR AUV POSITIONING?..........14
A.1.24 HOW IS SVP DATA LOADED INTO GAPS M5?.................................................... 14
A.1.25 HOW DO WE KNOW WHEN THE INS HAS FAILED IN THE GAPS?ERROR CODES? ...14
A.1.26 IS GAPS ABLE TO CHOOSE THE BETTER FREQUENCY ITSELF (IN NOISY ENVIRONMENT
FOR EXAMPLE)?................................................................................................................14
2.2 INTEGRATION AND MECHANICAL ASPECTS ..................................................................................14
A.1.27 HOW DELICATE IS THE HYDROPHONE ARRAY WHEN USING IT FROM A SMALL
VESSEL? 14
A.1.28 CAN GAPS M5 BE TESTED IN AIR?....................................................................14
A.1.29 HOW LONG WE CAN USE THE GAPS M5 IN AIR FOR TESTING? .............................15
A.1.30 CAN THE IP RANGE BE CHANGED TO A USER OWN NETWORK IP RANGE?...........15
A.1.31 IS THERE ANY DIFFERENCE BETWEEN GAPS M7 &GAPS M5 MOUNTING FLANGE
DIMENSIONS? ...................................................................................................................15

A.1.32 WHAT IS THE IDEAL DISTANCE BETWEEN LEVEL ARMS TO GAPS?....................... 15
A.1.33 CAN IUSE MY EXISTING GAPS CABLES?............................................................ 15
2.3 COMPATIBILITY .........................................................................................................................15
A.1.34 WHICH BEACON CAN WE USE WITH GAPS M5? MT8? MT9?.............................. 15
A.1.35 GAPS M5 HAS THE SAME ARCHITECTURE AS GAPS M7, SO CAN ITRACK 3RD PARTY
BEACONS LIKE IUSED TO WITH GAPS M7?......................................................................... 15
A.1.36 CAN ICONNECT IT TO MY MBES, DOES IT INCLUDE HEAVE?............................... 15
A.1.37 DOES IT SUPPORT THIRD PARTY SYSTEMS LIKE CNODE,HPR OR SONARDYNE WB?
16
A.1.38 DO WE NEED AN UPGRADE FOR WB1 OR IS IT A STANDARD FUNCTION?.............. 16
A.1.39 IF NO SCOPE FOR WB 2, IS THERE GOING TO BE ANY SCOPE FOR WB 3OR USING
6G+ COMPATTS?............................................................................................................. 16
A.1.40 ANY PLANS FOR CYMBAL FREQUENCIES –KONGSBERG CNODE COMPATIBILITY?16
2.4 MISCALLENEOUS.......................................................................................................................16
A.1.41 WHEN WILL THE M5 COME ON THE MARKET AND WHEN WILL IT BE AVAILABLE IN
RENTAL COMPANIES? ....................................................................................................... 16
A.1.42 DO YOU PLAN TO LAUNCH A GAPS M5 WITH A FLUSH ARRAY? ........................... 16

It is mandatory for USBL systems to be calibrated with an INS/AHRS on board of a vessel
to give accurate position and attitude to the USBL system. Calibration is not necessary with
Gaps M7 because it contains an INS inside of the USBL head. The calibration is done during
the manufacture process, making Gaps M7 a precalibrated system. No calibration is nec-
essary by the end user and Gaps M7 can be installed and be operational in less than an
hour.
Gaps M5 does not need to be calibrated, even after a hydrophone replacement.
Gaps systems mixes USBL, INS and GPS technologies to give the most accurate USBL
data in its category, it operates in deep or very shallow water and difficult environments
where other systems are deficient. As Gaps has an integrated INS, this allows its use with-
out a calibration. Where it is necessary to carefully calibrate all other USBL systems with
the INS on board, it is not necessary to carry out this calibration for Gaps, as it is pre-
calibrated at our factory with Phins/Octans inside. This will save a lot of time for users and
Gaps can be operational in less than an hour. The important point to know is that it is nec-
essary to align Gaps to obtain the best accuracy. This means that it is necessary that the
vessel stay with a constant heading during 5 minutes for the coarse alignment, then it is
necessary that it move in different directions for 25 minutes for the fine alignment. In only
30 minutes, Gaps will be ready to deliver you the specified accuracy.
By default the IP address is indicated on the Gaps BOX sticker and is 192.168.36.1XX, with
XX being the last two numbers of the serial number. If the IP address has been changed
and is not known, the following steps can be taken. If you have changed the address and
lost it, you can retrieve this IP address as follows: Connect a hyperterminal on the PC to
one of the RS232 sockets. Configure the terminal to the following settings: baudrate 115200
bds, data bits 8, parity: none, stop bits: 1. Reboot the unit by switching it off and on, the IP
address will be broadcasted by Gaps on the hyperterminal.

In order to get the best responses from your beacons, you must always set a blanking time
based on the recurrence you have set in the Gaps. The blanking time must always be -
200ms from the recurrence of the interrogations from the system. For example, if the recur-
rence is set to 1s, then you must configure the blanking time to 0.8s. Refer to Gaps user
manual for detailed tables for different examples.
For preventive maintenance:
In order to limit growth on the hydrophones, iXblue recommends the use of the following
anti-fouling: International - TRILUX 33
1. Sigman Coatings : blue Sigma-glide
2. They should be cleaned with isopropylic alcohol (Steps mentioned below)
3. Light abrasions with 100/120 sand paper
4. Clean with isopropylic alcohol
5. Wet the surface with aliphatic hydrocarbon solvent
6. Wait for 2 minutes to dry
7. Apply anti fouling according to the manufacturer’s recommendations (a
thin coating)
8. Wait for 24 hours
For curative maintenance:
To clean the hydrophones; use synthetic soap and water
To remove gwth, use ro180 sandpaper and apply minimal pressure on the hydrophone
In the configuration software, press F1. In this command menu, click "diagnostic button" to
access the battery diagnosis. When the transponder is connected to the charger, the
charger LED turns green when the battery is fully charged.
The level of the battery pack when fully charged should be around 8,5V (between 8,4V and
8,6V). The battery voltage level can be requested via the following steps:
1. Disconnect any external charger
2. Connect the transponder to the PC through the connection box
3. Launch the Transponder HMI interface
4. Press the F1 key

5. In the command utility window that appears, click Diagnostic button to
get the battery voltage.
The MT9 does not operate when the battery voltage is lower than 7V.
You must apply the same interrogation code to both responder and transponder modes in
the configuration software. If your responder signal is not sent to the beacon (in case of a
cable cut), the beacon will automatically move to transponder mode.
In this case it is necessary to have the same interrogation code so that you can continue to
follow your beacon. Keep in mind that it will be necessary to change the configuration of
both Gaps when the responder signal is not sent anymore.
Gaps M7 positioning accuracy depends mainly on Signal to Noise Ratio. This Signal to
Noise Ratio depends on the beacon transmit level, the range to the beacon, the noise level
and the vertical angle. In best case (SNR_in > 20 dB and in vertical conditions), the posi-
tioning accuracy is 0.1% of the slant range (CEP-50). i.e. 100 cm accuracy at 1000 m of
distance. If SNR_in is 10 dB, the positioning accuracy is 0.17% of the slant range (CEP-
50). For low SNR (around 0 dB), the positioning accuracy is 0.5% of the slant range (CEP-
50). When tracking horizontally, the positioning accuracy is 3 times less.
Gaps M5 positioning accuracy depends on the same criterias and is 0.5% of the slant range.
Gaps M7
The maximum range depends on the noise level and beacon transmit level. For a TL = 191
dB ref µPa :
•if noise level is 60 dB ref µPa: max range is 5 000 m (example of buoy
installation - SEA STATE 6 + 10 dB)
•if noise level is 70 dB ref µPa: max range is 3 600 m (example of quiet
vessel)

•if noise level is 80 dB ref µPa: max range is 2 300 m (example of a vessel
manoeuvring, Gaps at a reasonable distance from the thrusters)
•if noise level is 90 dB ref µPa: max range is 1 300 m (example of a vessel
manoeuvring, Gaps very closed from the thrusters)
Gaps M5
Gaps M5 maximum range is 995 m, making it free-of-export restrictions.
Try to use lever arms 10x as accurate as your measurement. For example, within 10cm for
a 1 m accurate GPS. This will make sure your lever arms will not affect the performance of
your system.
The Gaps systems cable can be 95m maximum long because of the limitation of Cat 5
Ethernet maximum length. If longer distances are required between Gaps head and Gaps
box, it is possible to connect 2 x 95 m cables through a repeater box (total length is then
190 m).
The reference point of the USBL is the SUBCON connector, on top of Gaps M7 and M5
heads.
Because of its specific antenna composed of 4 hydrophones, that form a tetrahedron. This
is a 3D antenna than enables to position a beacon with good accuracy on 3 axis (X, Y and
Z). Gaps M7 and M5 have an aperture of 200° which means we can track a beacon less
deep than the antenna.
Almost all navigation softwares have Gaps driver (QINSY, NAVIPAC, HYPACK, STARFIX,
WINFROG, GECDIS). If your navigation software is not in this list, Gaps M7 and M5 can
emulate third party protocols (GPGGA, SONARDYNE, KONGSBERG) Most of the time,

Gaps M7 must not be declared as a standard USBL system because this is a pre-calibrated
system. In QINSY for example, Gaps M7 and M5 must be declared as a positioning system.
To get Gaps M7 and M5 nominal accuracy, the measurement of the sound velocity in the
water column is mendatory. If the sound velocity profile is not measured and not configured
into Gaps M7 and M5, this can lead to unaccuracy and even to non positioning. If no sound
velocity probe is available on the vessel, statistical sound velocity profiles can be used.
Contact iXblue to get a tatistical sound velocity depending on your location and season.
The different possibilities are :
•increase beacon transmit level
•reduce noise received by the Gaps (increase the horizontal distance between
Gaps and source of noise, increase Gaps depth)
If positions are jumpy, this probably comes from a multipath (reflective surface which is too
close from the Gaps M7 or M5 or the beacon) and/or difficult conditions for acoustic propa-
gation (shallow water or horizontal tracking). Increase Gaps M7 or M5 depth or place differ-
ently the beacon transducer. If a bias is observed in the positioning:
•check beacon turn around time (in the beacon and in the Gaps web MMI)
•check that a correct sound velocity profile has been configured into the Gaps
•check the GPS lever arm and potential mounting misalignments.
Gaps M7 standard package comprises the Gaps M7 head, a 50 m cable and the Gaps M7
box. Beacons, other cable lengths, GPS antenna can be ordered separately.
Gaps M5 standard package comprises the Gaps M5 head, a 20 m cable and the Gaps M5
box. Beacons, other cable lengths, GPS antenna can be ordered separately.

Gaps M7/M5 are operated through an Internet browser (Firefox, Chrome, Internet Explorer,
Safari…) and operated from any device that runs an Internet browser (laptop, workstation,
computer, mobile, tablet...). It means that there is no restrictions regarding the Operating
System. iXblue recommends the use of Firefox because this is our qualification environ-
ment.
As far as possible from any source of noise (thrusters, propellers, engines...) and below the
wash created by the thrusters.
As far as possible from any source of noise (thrusters, propellers, engines...) and on top of
the ROV in order there is direct acoustic line of sight between the Gaps M7/M5 head and
the beacon transducer.
If the Gaps M7/M5 to GPS lever arm is small (< 5 m), Gaps mounting misalignment has low
impact. If the Gaps M7/M5 to GPS lever is bigger, it may have an impact and it is recom-
mended to enter these misalignments into Gaps M7/M5 web MMI (mechanical installation
parameters).
These misalignments can be estimated at sea (when INS correctly aligned) by comparing
Gaps M7/M5 heading roll and pitch to vessel heading roll and pitch. If the Gaps M7/M5 to
GPS lever arm are really large (20 m or more), it is recommended to compensate this lever
arm into a navigation software (QINSY, NAVIPAC, WINFROG...) and to input into Gaps
M7/M5 this compensated position.
Each type of beacon has its own characteristics (transmit level, directivity, type of signal),
the positioning performances are then different from one type of beacon to the other.