R/V Hugh R. Sharp Multibeam Echosounder System Review
Contents
1. Offset is Positive Downward and Measured Yaw rotation follows azimuth clockwise rotation is From Waterline positive Bow up is positive pitch port side up is positive roll Starboard 0 000 Yaw 0 00 Forward 0 000 Pitch 0 00 Vertical o 480 Roll fo oo Device Latency Enter the Latency Time Positive in Seconds Installed on Towfish Close Help About Applanix POS M Network X Figure 5 Hypack configuration of POSMV IMU offsets Note that Hypack insists that vertical offsets are measured from the waterline second paragraph in Position panel The configuration of the sonar head offsets in Hypack is shown in Fig 6 Note that it is possible to accommodate the varying transducer depth in Hypack by adjusting the sonar z offset in the HYSWEEP Hardware configuration module as shown in Fig 6 This approach however involves exiting Hypack s survey mode and it does not document the time that the keel depth was changed Without good survey line log keeping it would be difficult to recover from errors in this process since there is no record of when the keel depth was changed and to what value it was changed to Options to accommodate the variable keel depth should be explored with Hypack personnel 10 men s File Manufacturer Model Connect COM Test Network ref omes Sonat Head 1 Position Rotation This va ue va ries Enter Device Offset From Boat R2. an assumed depth and will depend on the actual depth when on site Survey lines are planned typically using the assumed depth and may need to be adjusted to ensure overlap 19 o The real time grid also facilitates quality assessment If there is a problem with the motion sensor or sound speed profile it will be noticeable in the grid and action can be taken to rectify the situation o This greatly increases the chances of noticing when a survey line has accidentally skipped during a grid survey since it is very noticeable if there s a hole in the real time grid matrix Miscellaneous Establish SOPs for various logging scenarios Hypack logging POSMV logging 7kCenter logging Document pros cons of each method to help inform science party decisions on what mode of acquisition works best for their needs The MAC can assist with this during a future visit The water line offset should be measured pre and post cruise This value should be adjusted in Hypack and noted in the multibeam acquisition and or processing log along with time of measurement A meter stick should be installed in the auxiliary engine space and zeroed at the height of the IMU instead of relying on marks on the wall to measure water level Signage should be installed alongside the meter stick to indicate to all personnel the importance of the exact placement of the meter stick in the event that it needs to be removed In addition to being used to adjust the sonar z off
3. immediately following Hurricane Sandy Nov 10 2012 and attest to the quality of the installation and the integration of the survey system components The system was seen to suffer from bubble wash down effects during the pre Hurricane Sandy survey where wind speed was steadily increasing Further testing should be done to better appreciate the degradation of data quality with wind speed and sea state These types of studies which can typically be done in less than one day lead to improved ability to assess whether or not the system will be limited by weather conditions and can aid in management of survey system assets and can help answer questions like should we even bother going out in this weather The MAC is prepared to contribute personnel for planning acquisition processing and analysis if time for testing can be arranged The range of depths encountered throughout the testing trials did not exceed the maximum range of the system It is recommended to obtain data over a larger range of depths to better understand the range limitations of the system for both 200 kHz and 400 kHz modes and to establish practical working limits for the system The MAC is committed to providing personnel for these additional tests if they are desired Due to the shortened technician training period it is recommended that follow up training be sought on the operation of the Reson 7125 The MAC can provide training and or can provide recommendations fo
4. offsets from sonar frame and sonar head from the MB plate in the original survey Acquisition Configuration The systems on RV Hugh Sharp can be configured in a number of ways to accommodate various data logging requests The current acquisition configuration has been found to be the most stable and is recommended for all future surveys e Hypack records POSMV navigation and orientation via the network and only records the bathymetry data from the Reson 7125 It was found during the 11 installation and calibration trials that the Hypack software was highly unstable when recording Reson snippets and sidescan data Testing should be done to determine if stability improves with only the snippets data being recorded Raw data are stored in HSX data files in each project s Raw subdirectory If science parties are interested in acquiring seabed imagery the most stable solution found during the trials was to have the Reson 7kCenter software record the sounder data in s7k files A series of record type filters must be set such that the appropriate data records are recorded Refer to Fig 7 Again Hypack may prove to be stable when only recording the snippets data but not the sidescan data The Hypack driver for the Reson 7125 is currently configured to send start stop logging commands to the Reson software during such events in Hypack such that the operator only needs to start stop logging in Hypack Refer to F
5. pod 3 An additional offset to accommodate for the distance from the bottom of the sonar pod to the transducer s reference point typically the center of the projector The Reson technician measured the offsets associated with 2 and 3 but only provided the total offset of 4 29 m when the drop keel is deployed flush with the hull Furthermore the measurements made by the technician indicate a slight along ship offset between the sonar plate and the sonar head the sonar head is 8 7 cm aft of the sonar plate presumably this is due to the shift between the sonar plate and the sonar head s reference point again this is typically the center of the projector The drop keel system can be deployed in four configurations Retracted into the hull Flush with the hull sonar z offset is 4 29 m relative to the IMU 1 meter proud of the hull sonar z offset is 5 29 m relative to the IMU 2 meters proud of the hull sonar z offset is 6 29 m relative to the IMU mw Ne Sensor and software configuration for offsets The offsets are placed as follows in the POSMV and Hypack configurations after allowing for changes in sign conventions and shifts of origin as explained below No offsets are entered into the Reson configuration except for the relative offsets between the 7125 transmitter and receiver these are pre configured according to the mounting bracket sold with the unit and should not be modified It is important to point out that
6. water level and was measured as 0 48 m below the IMU see Fig 3 0 48 m Height of top of POSMV IMU 0 48 m above the water line POSMV IMU POSMV IMU viewed from entrance to engineering space Water line as measured dockside on Oct 24 2012 Figure 3 Measurement of water line relative to POSMV IMU The vessel offsets are summarized in Table 1 using the same coordinate system described by the 2009 survey e The positive along ship axis points towards the bow e The positive athwart ship axis points to starboard e The positive vertical axis points upward Table 1 Summary of Vessel Linear Offsets in 2009 Survey Coordinate System Object X m positive Y m positive stbd Z m positive up forward POSMV IMU 0 00 0 00 0 00 Water line 0 00 0 00 0 48 Sonar plate 1 68 0 125 0 402 POSMV GPS 4 980 1 804 15 795 port POSMV GPS 4 947 1 940 15 792 starboard Sonar head 1 767 0 125 4 29 drop keel flush with hull The drop keel holds four pods that can accommodate a variety of sensors with the multibeam sensor in the forward most pod Assuming that the Sonar plate referred to in the 2009 survey is the top of the pod when in the flush position the total multibeam vertical offset is determined through the following 1 0 402 m below the RP to the sonar plate 2 An additional offset to accommodate the vertical extent of the sonar
7. 09_survey 0 48 For example the sonar z offset is calculated as Zhypack 4 29 0 48 3 81 And the POSMV IMU z offset is calculated as Zhypack 0 00 0 48 0 48 Water line offsets should be measured before and after survey cruises to capture draft variation with fuel consumption etc The water line z offset should be used to adjust Hypack z offsets for the POSMV IMU and the Reson 7125 in Hypack using the examples above as a guide All adjustments should be documented in the survey acquisition log The POSMV provides the position of the IMU to Hypack thus Hypack does not require entry of the POSMV antenna offsets as mentioned earlier entering these offsets will create a positioning error as they will be doubly corrected for The only offset entries required in Hypack are those of the multibeam head and the IMU with respect to the water line position immediately below the IMU Table 2 summarizes the offsets as entered into Hypack Fig 5 shows entry of the POSMV IMU values in Hypack Table 2 POSMV and Reson offsets as configured in Hypack Object Along ship m Athwart ship m Vertical m positive forward positive to positive down starboard POSMV IMU 0 00 0 00 0 480 Reson 7125 0 125 1 767 3 807 M Position Rotation Enter Device Offset From Boat Reference Point Center Enter Device Rotation from Forward Yaw and Vertical of Mass Roll and Pitch The Vertical
8. 5 signal relative to a signal level ceiling at which the sonar will be driven into a non linear response regime The software was left installed on the Reson Hypack PC in anticipation of future cruises in 2012 2013 during which the author will use the software Training was provided to the technicians on how to run the software but more documentation should be provided on the installation process and background theory The software is considered experimental and should not be used for other cruises without consulting the MAC as its misuse could lead to significantly degraded seabed imagery data quality 15 Configuration Documentation Cookbook style documentation has been provided to the technicians to document and to facilitate verification of system configuration for the POSMV Reson 7125 and Hypack These provide detailed step by step instructions that allow those who are not necessarily intimately familiar with the system to verify critical system settings prior to a mapping mission These documents are continually updated and newer versions can always be found on line at http mac unols org Softcopy versions of each of the three documents were provided to the marine technicians in both PowerPoint and PDF format such that updates can be done by technicians to the PowerPoint files and propagated back to the MAC to update copies on the MAC website System Performance A short survey was undertaken immediately after the installation on
9. October 26t as part of a mapping cruise led by Dr Art Trembanis of the University of Delaware This cruise allowed for preliminary assessment of the mapping system s capabilities After a patch test data were acquired over the Red Bird reef site approximately 15 NM off the coast of Delaware Bay in 27 m of water Conditions at sea were fair at the beginning of the short cruise but began to degrade toward the evening with the approach of Hurricane Sandy Bubble wash down events degraded the quality of seabed imagery and bathymetry leading to data artifacts in mapping products derived from these data see Fig 9 The area was mapped in two parts with a 7 hour break in between to return the Reson technician to shore and conduct other science operations The first half of the survey was conducted with the drop keel deployed 1 m and the second half of the survey having the keel extended to 2 m Bubble wash artifacts affected data quality in both configurations however it is difficult to discern which of the two configurations is less prone to wash down events due to the long break between the surveys over which wind and sea conditions changed Though it was initially planned to map the area twice once at 400 kHz and again at 200 kHz there was insufficient time and only the 400 kHz coverage was obtained 16 lower left The wash down related artifacts are correlated with survey line orientation they are worse on every second line and thus ap
10. R V Hugh R Sharp Multibeam Echosounder System Review Multibeam Advisory Committee Sea Acceptance Team October 31st 2012 Report prepared by Jonathan Beaudoin Center for Coastal and Ocean Mapping Joint Hydrographic Center University of New Hampshire Durham NH This material is based upon work supported by the National Science Foundation under Grant No 1150574 Table of Contents Introduction aie csi seste cd bec a cesuced sacked cedacdcdiauesdadecad danshcaeausddacdateid sddacsatencdsatelencudaas uucstucdatatieizaccteese 3 Survey System COMPOMNENUS cscsssssccssseeeseesenseeenseeeesesesaesnsasenseeessneeeseeneseeeesaesaesesanseseeeseeanseeaeses 3 PN CONVICTS E A A EE A EAE A E E A A E 3 System GEOmMetrTy occas ncnadeceasansnsninensnatatubansnnesaauenmansadnenaandaneaninnhsandbannnsssactannnaidannsivansdiusVenninanndias 4 Sensor and software configuration for offsets s sessusuususuununuununnununnnnunnnnunnnnununnunnnnnnunnnnnnnnnnnnn 7 Acquisition Configuration ss s sesssssessussusunnunnnunnennnunnnnnnunnnnnnunnnnnnunannnnannnnnnanannnnnnnnnnnnnnn annaa 11 Operator Manuals and Training Material sssssssusnsuusununnunnnunnennnunnnnnnunnnnnnunannnnannnnnnannn 14 Deployment of MAC Software Tools Utilities and Documentation 00 15 KATA A EDLE BROTTET EEEE EE E EEEE E EE EEE E 15 SELRIUR AELOD ION LOD oU iE O eE EE E 15 Configuration Documentation cceccsseeeeessesseeeeeseesinseeeeeensenseseeeseeeee
11. U s n 5250 HW1 1 10 SW06 13 Aug24 11 e Seabird 911 conductivity temperature depth CTD sensor e Hypack 2012 data acquisition software Activities The ship visit occurred during a pre cruise mobilization from Oct 24 and also included part of the following cruise due to time constraints imposed by Hurricane Sandy System installation was largely completed prior to the visit by Tim Deering and was fine tuned by the Reson technician on October 24th A patch test calibration procedure was completed in Delaware Bay by the Reson technician on October 25th followed by training in Hypack and Reson software by the visiting Reson technician for the shipboard technicians Training was continued on October 26 along with a test mapping survey during a shortened science cruise 15NM offshore of Delaware prior to the arrival of Hurricane Sandy A second ship visit was made by Beaudoin on Nov 9 to make up for the lost time due to Hurricane Sandy Further vessel geometry and software configuration documentation was acquired System Geometry In this report we use the term system geometry to mean the positional and angular offsets of the various components of the multibeam mapping system These parameters are critical to being able to collect soundings in an unbiased and repeatable manner The general arrangement of multibeam mapping system sensors is shown in Fig 1 Note that the sonar head is deployed on a drop keel with variable depth settings Fig
12. double entry of offsets is a common source of positioning bias in multibeam echosounding data and that care should be taken to avoid this For this particular installation the POSMV is only configured with the offset to its primary GPS antenna All other offsets both linear and angular are configured in Hypack Incorrect offsets in the POSMV are difficult to recover from Incorrect offsets in Hypack are recoverable as long as the correct offsets are known through post processing in software such as Caris HIPS or in Hypack itself Applanix The POSMV IMU is set as the reference point in the Applanix software thus offsets in Table 1 do not require any shift of origin The only offset entered in the POSMV configuration is that of the primary starboard antenna The position of the secondary antenna is established through the built in GAMS calibration routine The Applanix coordinate system differs from the 2009 survey in the positive direction of the z axis thus the starboard antenna s z offset becomes 15 792 m as shown in Fig 4 With the POSMV configured as such the reported position sent to Reson or Hypack acquisition via Ethernet or serial cable will be the position of the POSMV IMU itself Post processing software should typically not be configured with the POSMV primary GPS antenna offsets since the reported positions are corrected for this already Lever Arms amp Mounting Angles ensor Mounting Tags AutoStar
13. eference Point Center Enter Device Rotation from Forward Yaw and Vertical of Mass Roll and Pitch with the drop keel The Vertical Offset is Positive Downward and Measured Yaw rotation follows azimuth clockwise rotation is deployment From Waterline soy Bow up is positive pitch port side up is positive tol configuration 2 m gt 5 807 m Starboard ms Yaw Patch test 1m 4 807 m Forward 1 767 Pitch offsets are 0 m gt 3 807 m Vertical 5 807 Roll entered here Device Latency Enter the Latency Time Positive in Seconds 0 000 Installed on Towfish Close Help About Reson Seabat 7125 Access under HYSWEEP menu choose HYSWEEP Hardware Figure 6 Hypack configuration to accommodate differing keel deployment scenarios Note that Hypack insists that vertical offsets are measured from the waterline second paragraph in Position panel Also note that the patch test offsets as determined by the Reson technician are entered into the Reson 7125 sonar head offsets in the Rotation panel of Fig 6 Recommendations include e Documentation for the 2009 survey should be found and included in the survey configuration documentation If sufficient documentation for the existing survey drawings cannot be found a repeat survey should be performed at the next dry dock e Photo documentation of various system components and measurement procedures to ascertain additional x y z
14. esenaeneasensanaeseeesesanenseeeeees 16 System Pr lO PIANC oa ses chs ssnauccatucrannnstitcsanecsasiunrnecentcanansannticaanscunissmnnecantdaamsanteavaasnianmtuaynnleail 16 Principal Findings and Recommendations ssssssssssssssununsnnunnnnnnunnnnnnununnnnnnunnnnununnnnnnnnnnn 18 REPO NCGS wiiscevesecucsisecedcesccatesaus eesuevadewtersonscasdeusyesduevavadecacusnevedoaucecadz cuseressaudieseuudedumuvsvetecueuene 21 Any opinions findings and conclusions or recommendations expressed in this material are those of the author s and do not necessarily reflect the views of the National Science Foundation Introduction R V Hugh R Sharp undertook an informal sea acceptance test and training session in support of the vessel s Reson 7125 multibeam echosounder in the vicinity of Lewes DE from Oct 24 26 2012 Participants in the installation calibration and training were e Timothy Deering UDEL e Wynn Tucker UDEL e Ted Cummiskey UDEL e Brian Kidd formerly of UDEL e Justin Friesner Reson e Jonathan Beaudoin UNH The author participated in the activities as part of the NSF funded Multibeam Advisory Committee MAC project an effort to improve the data quality from multibeam echosounders in the U S academic fleet Survey System Components The mapping system consists of the following components e Reson 7125 SV2 FP3 multibeam echosounder 200 400 kHz with surface velocimeter e Applanix POSMV V5 inertial measurement unit IM
15. ience parties without access to Hypack Hypack HSX data can be brought into multibeam data processing software such as Caris HIPS for further corrections e g sound speed profile refraction corrections tides angular corrections with patch test offsets This particular processing path does not allow for seabed imagery backscatter or multibeam sidescan processing as the Hypack installation on the vessel was found to be unstable when recording snippets data Further testing could be done to determine a stable Hypack configuration in which snippets data could be recorded If this is desired the user must check the Log Seabat Datagrams checkbox in the Reson Setup dialog shown in Fig 8 This will record a 7K file alongside each HSX file and will allow for backscatter processing in Hypack or other commercial software packages Operator Manuals and Training Material Softcopy and hardcopy operator manuals were available for the Reson 7125 system As the Reson 7125 was new to the vessel very little training material had been assembled Training was cut short due to Hurricane Sandy shifting a cruise forward in time 14 Deployment of MAC Software Tools Utilities and Documentation SVP Editor SVP Editor is an application that provides pre processing tools to help bridge the gap between sound speed profiling instrumentation and multibeam echosounder acquisition systems This software was developed and is maintained by the Mul
16. ig 8 POSMV should record raw POSPAC data to accommodate post processing of TrueHeave or to perform an ellipsoidally referenced survey ERS These data should be recorded at a high rate 100 Hz if they are being used to correct for roll pitch and heading If they are only being used to correct for TrueHeave or for ERS the data rate can in theory be lowered however this limits the usability of the POSMV raw data records in the event that Hypack orientation data are corrupt and it is suggested to maintain the 100 Hz data rate at all times 12 Select data to add to minimal set V Snippets Sidescan Sensor Data Motion Position Heading etc Watercolumn includes Sensor Data Troubleshooting Indudes Watercolumn BITE ox cancel Figure 7 Data recording setup in Reson 7kCenter to enable seabed imagery acquisition 13 Lo e lfata Use Snippets Log Seabat Datagrams 8101 Driver 101 1028 81xx Drivers r None 7K Drivers Datagram Version 1 Snippet Samples per Beam C Datagram Version 2 25 woning raren a onies may Transmitter Offsets from Receiver change when switching between datagram versions 0 000 0 000 0 000 JV Send Start and Stop Logging Commands to the Seabat Dual 7125 Driver r Cancel Figure 8 Hypack driver configuration for Reson 7125 allowing for remote start stop logging commands to be sent to the Reson 7125 from Hypack For sc
17. pear to have a heading dependency A second mapping survey was completed over the same site on November 10 2012 again with Dr Art Trembanis of UDEL Sea conditions were excellent with 2 ft seas and light winds Data quality was excellent at 400 kHz The area was mapped a second time at 200 kHz but the data suffered from increased self noise levels at this frequency leading to bottom tracking artifacts It should be noted that the primary goal of the 200 kHz survey was to acquire high quality acoustic backscatter data within the linear regime of the sonar s receiver The saturation monitor indicated that the source level should not exceed 195 dB this is much less that what the manufacturer typically recommends in order to achieve high quality bottom tracking across the swath The problems with decreased signal to noise ratio SNR associated with the low power setting could be due to the configuration particular to this survey and not indicative of achievable performance at higher source levels at the cost of saturated backscatter measurements 17 Principal Findings and Recommendations The Reson 7125 system is correctly installed and integrated with the POSMV and Hypack acquisition system and there is no indication of errors in the integration of the systems There remains uncertainty in the absolute accuracy of the depths due to the inadequately documented sonar z offset calculation High quality surveys were collected during the cruise
18. r different training solutions The training should be Reson specific as this type of sounder requires much more involved planning and operation as compared to sounders on deep water vessels in the US academic research fleet Additional sensor and or software specific recommendations are listed below Reson Define a safe default set of operating parameters and save configuration files in safe location on network and on land in read only format use this to reload safe settings for each project as system settings will slowly wander from ideal settings with varying operators from cruise to cruise 18 Get 2 4 network card in Reson machine put it on the ship network to allow for data backup transfer etc this enables science parties to do near real time QC The Reson sound speed probe velocimeter should be occasionally checked against the CTD and TSG online calculators to compute speed of sound from TSG can be found at http resource npl co uk acoustics techguides soundseawater content ht ml the calculators are java scripts embedded in the webpage that can be saved locally for use when there is no internet connectivity POSMV Backup the configuration file on the network and off ship the configuration files should be date time tagged and made read only There was a write error message report by the POSMV the manufacturer should be contacted about this A network switch should be added in the topside rack to allow fo
19. r local monitoring and recording of the POSMV on the bridge The POSMV data should be recorded for all surveys to improve heave corrections or to allow improved vertical horizontal positioning It is strongly recommended that logging start at beginning of cruise and stop at end of the cruise for a number of reasons o Minimize human error in start stop logging process During mapping cruises a request to suddenly begin logging the multibeam data may occur as a scientist walks by the multibeam display and it is beneficial in these cases to have the POSMV logging already o Eases post processing tasks file management becomes difficult when the POSMV data are broken over several missions o Provides a continuous tidal signal for other science mission instrumentation low pass filtering the POSMV height data can provide tidal correctors for other instrumentation deployed during a cruise Hypack Establish a safe default project that is configured for all mapping sensors and offsets that you can quickly bring online in the event of Hypack project file corruptions that detract from system stability Establish a set of SOPs to create Hypack projects acquire and evaluate patch test calibration data process data It is important to configure Hypack such that it is gridding the sounding data into its matrix This is important for three reasons o This helps ensure desired coverage is being achieved The planned amount of swath coverage is based on
20. set in Hypack the drop keel deployment depth should be noted in the acquisition log for every survey Along with the uncertain sonar z offset from the installation process this is potentially the largest potential source of error in this particular installation A clear and concise SOP should be developed to avoid this potential source of error Along the same lines the Reson technician should be contacted to request installation and calculation notes to establish the method used to calculated the sonar z offset The z offset measurement process and calculation should be repeated by technicians with the aid of the MAC if desired and documented such that others could repeat the procedure 20 References Beaudoin J 2012 SVP Editor Software Manual Version 1 0 3 Sept 21 2012 available online via anonymous FTP at ftp ftp ccom unh edu fromccom MAC_DATA svp_editor v1 0 3_20120921 SVP 20Editor 20Manual 20v1 0 3 pdf 21
21. t Ref to IMU Target IMU Frame w rt Ref Frame Target to Sensing Centre Resulting Lever Arm X m 0 008 X deg fooo0 X m _ 0 008 X m 0 000 Y m 0 031 Y deg o 000 Y m 0 031 Y m 0 000 Z m o0 Z deg o0 Z m fo130 CO Z m fooo0 OS Ref to Primary GPS Lever Arm Ref to Vessel Lever Arm Ref to Centre of Rotation Lever Arm X m _ 4 947 X m 0 000 X m 0 000 Y m 1 940 Y m 0 000 Y m 0 000 Zm 15 792 Z m 0 000 Z m 0 000 Notes 1 Ref Reference 2 w r t With Respect To 3 Reference Frame and Vessel Frame are co aligned ni View In Navigation Mode to change parameters go to Standby Mode Figure 4 Applanix POSMV configuration of primary GPS lever arm offset Hypack The reference point as configured in the Hypack installation is the position of the POSMV IMU Hypack requires vertical offsets be referenced to the water line thus all z offsets must have 0 48 m removed to make them relative to the water line The reference point from the Hypack point of view is now the position of the POSMV IMU projected down 0 48 m to the water line As with the Applanix coordinate frame convention the direction of the vertical axis differs in sign with respect to the 2009 survey thus the sign of all z offsets are changed After the water line origin shift all z offsets must have their signs reversed Any z coordinate can be transformed as such Zhypack Z2009_survey 0 48 x 1 Z20
22. tibeam Advisory Committee MAC and is freely available online at http mac unols org This software has been installed on the CTD processing machine and training has been provided to all MTs The software supports the Seabird CTD cnv sensor output format available on Hugh Sharp and provides for graphical data interaction in which the operator can validate measurements remove outliers and extend profiles beyond their maximum sampling depth using oceanographic databases or user specified reference casts After processing the SVP Editor can export the cast into a format compatible with Hypack vel or Caris HIPS svp It is recommended to use this software to process and upload all sound speed information for the Reson 7125 The software is routinely updated more information can be found on the MAC website at mac unols org Further information on the SVP Editor can be found in the user s manual Beaudoin 2012 Saturation Monitor An experimental signal saturation monitor Saturation Monitor was installed on the Reson Hypack PC in support of a research cruise immediately following the Reson 7125 installation in which the author participated The software was developed by LTJG Glen Rice of NOAA OCS while stationed at UNH s Center for Coastal and Ocean Mapping Joint Hydrographic The software is based on graduate research conducted by LT Sam Greenway also of NOAA and is designed to monitor the received echo strength of the Reson 712
23. ure 2 is a photograph of the arrangement of POSMV GPS antennae on the forward mast lt _ POSMV GPS antennae RV Hugh R Sharp Multibeam mapping system general layout UY A mi ya NV i POSMV GPS antenna primary starboard Note placement of sensors is not to scale Figure 1 General layout of multibeam mapping system components Figure 2 POSMV GPS antennae on forward mast as viewed from astern In these types of visits the MAC usually examines existing reports ship drawings and records of survey configuration changes with the aim of independently coming to a set of linear and angular offsets for the ship mapping system components The only documents available for review consisted of a 2009 survey summary drawing that documented offsets of the two POSMV antennas and the sonar plate both of which are with respect to the POSMV IMU Measurements were provided in feet and in meters however the sign of the offsets was not carefully transferred between the two systems and care should be taken when referring to this document The water line offset with respect to the IMU was established by running a clear hose from a through hull fitting up to the auxiliary engineering space where the IMU is installed The seacock was opened while dockside and a mark was made on the wall opposite the POSMV IMU The height difference between the reference point top of the POSMV and the waterline was determined via a
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