Perspective-MB. -- Bathymetry Processing Guide. Kongsberg.ALL Addendum

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1 Perspective-MB -- Bathymetry Processing Guide Kongsberg.ALL Addendum By: Tony M. Ramirez November, 2013

Triton Imaging Inc. Engineering Office 2121 41 st Avenue, Suite 211 Capitola, CA 95010 USA +1-831-722-7373 +1-831-475-8446 sales@tritonimaginginc.com support@tritonimaginginc.

2 Triton Imaging Inc. Engineering Office st Avenue, Suite 211 Capitola, CA USA TRITON This user guide is provided as a means to become familiar with TRITON s software through an explanation of the options available for processing bathymetry data. The user interface presented in this guide is subject to change to accommodate software upgrades and revisions. While every precaution has been taken to eliminate errors in this guide, TRITON assumes no responsibility for errors in this document. Users of this document are required to have a valid license for Perspective and BathyOne in order to activate the software. TRITON hereby grants licensees of TRITON s software the right to reproduce this document for internal use only. Page ii

3 Table of Contents 1.0 Introduction ALL to XTF Converters Legacy ALLtoXTF Converter New ALLtoXTF Converter LOG Files Run Parameters Sound Velocity Files Vessel Geometry Geometry Dialog Offsets from the Point of Reference Patch Test Results Data Multipliers Heading and Heave Offset Diagram Geometry Settings for Processing XYZ Depth Solutions Geometry Settings for Processing Raw Bathy Data Summary... 7 Page iii

4 1.0 Introduction This document presents additional information for processing Kongsberg multibeam data. Since most Kongsberg multibeam data is collected as.all files by their SIS acquisition software, options for converting the.all file to.xtf need to be presented. It is also important to discuss the vessel geometry dialog in Perspective and how to properly complete it for the converted data. 2.0 ALL to XTF Converters We currently have two versions of our ALLtoXTF converter to provide users, depending on the sonar model used to acquire the multibeam data. Our traditional ALLtoXTF converter extracts the real-time bathy depth solution determined by the SIS software at the time of acquisition, while the new ALLtoXTF converter allows the user to choose whether to output the depth solution or the raw beam angle/range data. At the time this document was written our new converter only works for EM2040, EM3002 and EM710 multibeam sonars. All other EM sonar data should be converted using the older legacy converter. Note that there is a separate install for each and they both can be installed at the same time. To download the ALLtoXTF converters use the links below: Legacy Converter New Converter Legacy ALLtoXTF Converter Triton s legacy ALLtoXTF file converter writes the XYZ depth solution for each sounding into the XTF file format, preserving the raw motion data and ping header information as well. Note that the depth values determined have already been corrected for the vessel motion (pitch, roll & yaw) and have a SVP applied by the SIS software, however heave has not and still needs to be considered (see Section 3.1.3). Using the legacy AlltoXTF converter is fairly simple and really only includes 2 buttons for most operations. Add Files will allow the user to select which files to convert. Once the Page 1

files are added, selecting Convert Files will write one XTF formated file for each input.all file into the same directory as the converted.all files.

5 files are added, selecting Convert Files will write one XTF formated file for each input.all file into the same directory as the converted.all files. Note that processing XTF files with the XYZ depth solution in Perspective is more than just gridding the sounding data with the existing depth solutions. The BathyOne processing wizard allows the user to adjust the depth solution for vessel heave, set beam suppression filters to eliminate noise, apply a sound velocity profile (if not done during acquisition), and adjust the depth solution for tidal fluctuations. 2.2 New ALLtoXTF Converter Triton s new ALL file converter appears the same as the legacy converter, except for the addition of two checkboxes. These checkboxes allow the user to create XTF formatted files with raw beam angle/range data (Store Raw Bathy if Present) or the determined XYZ depth solution (Store Bathy Only). Note that it is possible to select both options and generate both types of XTF files at the same time. The converted raw bathy XTF files will have a _RAW appended to the file name so they can be distinguished from the bathy only files. Shown right is an example of the new ALLtoXTF converter. The output from the bathy only option is identical to the legacy converter output with the same processing options available LOG Files The raw bathy output however includes a.log file for each.all file converted that describes the type and number of packets converted as shown to the right. Page 2

2.2.2 Run Parameters Also output from the raw bathy conversion is a file called: <filename>_runparams.txt This file will be generated for the first file in the list of.

6 2.2.2 Run Parameters Also output from the raw bathy conversion is a file called: <filename>_runparams.txt This file will be generated for the first file in the list of.all files to convert, and again for any.all file in the list that has different values for these parameters. This file should be reviewed prior to processing the XTF data files to make sure they have been properly converted. As shown in the example to the right, there are a few parameters which can quickly identify if the data was read correctly. Since a 1 degree beam width is correct for this sonar and 70 degree coverage for the port and starboard channels seems reasonable I know the.all data files were properly read and converted Sound Velocity Files Sound velocity profiles can be applied during acquisition with Kongsberg s SIS software and recorded into the.all file. The sound velocity profile entered is applied to each ping until a new profile is entered, which will then be applied to each subsequent ping. During conversion of the.all file, each unique sound velocity profile in the converted files will be extracted to a.txt for use in processing the raw bathy data. To use the extracted sound velocity profiles, Perspective s XML Utilities needs to be used to parse the text files and create.svp_xml files for use in the BathyOne processing wizard. Note that it is important to note the location of the sound velocity profile when it is collected because this information is not saved in the.all file. Details on using the XML Utility are presented in the Bathy Processing Guide available from the following link: Page 3

3.0 Vessel Geometry Another important consideration when processing Kongsberg.ALL files is making sure the vessel geometry file is properly setup.

7 3.0 Vessel Geometry Another important consideration when processing Kongsberg.ALL files is making sure the vessel geometry file is properly setup. Vessel geometry can be tricky and getting it right is critical to get good results from processing. 3.1 Geometry Dialog Below is an example of the Vessel Geometry dialog with the different regions grouped by the type of information that needs to be entered. Page 4

8 3.1.1 Offsets from the Point of Reference The point of reference on a vessel is often chosen to be the vessel s center of mass, the location of the primary GPS antenna, or the location of the multibeam sonar head. Offsets from the chosen reference point position need to be recorded and entered into the Vessel Geometry dialog Patch Test Results Results from patch test ran during data acquisition need to be entered in the Roll, Pitch, Yaw, and Latency fields. Note that the latency is divided into 4 sections depending on the latency source Data Multipliers This section is very important and should not be overlooked. The default multiplier of 1 indicates the values recorded in the motion packets within the XTF data file will be used and applied during processing. If motion data has already been applied, such as in the XYZ depth solution data, then the multipliers for the motion fields need to be set to 0. Note that the bottom multiplier is for the depth value and allows the user to apply a scaling factor to the depth. Also, for all Kongsberg sonars, their Z value is positive up so to properly apply the heave correction a -1 needs to be entered in the Heave multiplier field Heading and Heave The top field is for the Heading Offset (in degrees) which is very similar to the Yaw patch test correction but generally is used for larger offsets such as between the surveyed ship center line and the gyro compass. The middle field is for the measured distance between the chosen vessel reference point and the mean water line. This can be difficult to measure in heavy seas, but measuring the maximum and minimum depths of a swell and taking the mean gives fairly reliable results. The bottom field is for the vessel draft and automatically completes depending on the heave reference point selected in the drop down menu below it. Heave data coming from modern motion reference units (MRUs) often can calculate the actual heave at the transducer based on the vessel geometry offsets entered in the MRU. If the offsets between the MRU and the transducer are entered, the true heave value can be recorded. It is important to document how this was setup during acquisition so the data processor knows how to properly complete the Vessel Geometry dialog. For files with true heave, Page 5

9 the heave reference point needs to be set to the transducer so the correct draft is applied to the heave values Offset Diagram A very important item to consider when completing the Vessel Geometry dialog is the vessel offset diagram to know which directions are positive so the correct sign is used for the entered values. For offsets in Perspective, positive Y is forward, X is starboard, Z is down, with positive clockwise rotations looking down for yaw, starboard for pitch, and forward for roll. 3.2 Geometry Settings for Processing XYZ Depth Solutions Shown to the right are the geometry settings to use for processing the XYZ depths. Since the vessel offsets, roll, pitch and yaw have already been applied in Kongsberg s SIS software, to process the XYZ depth data most of the Vessel Geometry dialog is filled with zeros. The only exceptions are the Heave multiplier set to -1 and the Depth multiplier set to Geometry Settings for Processing Raw Bathy Data Vessel geometry values are not saved in the.all file and need to written down during acquisition for post processing using the raw bathy data. It is also important to note whether or not the beams were pitch corrected during acquisition and if so set the Pitch multiplier to zero for processing. Shown on the next page is an example Vessel Geometry dialog used for processing raw beam angel/range data extracted from.all files. Page 6

Looking over this Vessel Geometry dialog we can tell the MRU was used as the vessel point of reference since all the offsets are set to zero. The Antenna is located 0.79m directly above the MRU.

10 Looking over this Vessel Geometry dialog we can tell the MRU was used as the vessel point of reference since all the offsets are set to zero. The Antenna is located 0.79m directly above the MRU. Transducer 1 is 3.22m forward and 0.2m below the MRU with both Roll and Yaw corrections entered. The height of the reference point (MRU) above the water line combined with the Transducer 1 Z-offset gives a total draft of 1.61m referenced to Transducer 1. For data multipliers, note the Pitch is set to since the beams were pitch corrected during acquisition. Also the Heave multiplier is set to to account for difference in the vessel positive Z-direction between the Kongsberg sonar and the convention used by Perspective. 4.0 Summary Trito n provides two options for converting Kongsberg.ALL data files for processing in Perspective. A legacy version which provides the XYZ depth solution or a new version which allows the user to reprocess the raw beam angle/range data. Currently the new version only works with a select list of EM sonars. If there is a particular sonar model you would like added to the new conveter, please contact our support department at: support@tritonimaginginc.com Page 7

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