Performance Testing 10/11/2014HYPACK® Multibeam Training Seminar2 Questions We Might Ask About Our Multibeam Data: repeatable is the Multibeam?How repeatable is the Multibeam? Out to ‘what’ Beam Angle can I use?Out to ‘what’ Beam Angle can I use? compare with Single Beam?How does it compare with Single Beam? Two Performance Tests in MBMAX Help to Answer Beam Angle TestBeam Angle Test – Shows multibeam repeatability vs. beam angle. Single Beam TestSingle Beam Test – Compares multibeam vs. single beam depths. Compare results to standards. Bottom TypeHardSoft Maximum Outlier1 ft1 ft Max. Mean Bias<0.1 ft<0.2 ft 95% confidence depth < 15 ft±0.5 ft ±0.5 ft depth 15 – 40 ft±1.0 ft ±1.0 ft depth > 40 ft±1.0 ft±2.0 ft From Table 3-1: Minimum Performance Standards for Corps of Engineers Hydrographic Surveys
Reference Survey 10/11/2014 HYPACK® Multibeam Training Seminar3 Location Small area with a very flat, uniform bottom. The flat surface is to prevent DGPS position errors from influencing the results. Using lots of overlap and a narrow swath we get the best possible estimation of depth. Preparation and Survey Two sets of seven (7) parallel lines. Separation = Water Depth. Reference MTX with 1’ x 1’ cells. Survey at low or high tides to minimize errors. (SV cast immediately before survey) Survey the 14 Reference lines. Survey the Check lines (middle lines NS and EW). Flat, uniform reference area. Survey grid.
10/11/2014HYPACK® Multibeam Training Seminar4 Reference Survey to Surface XYZ Load reference survey into MBMAX. Apply tide and SV corrections. Filter to +/- 45 degree angle limit. Edit out remaining flyers. Use the reference MTX file for Area Based Editing. Save cell averageSave cell average (minimum 3 soundings per cell) to Reference XYZ. Processing Full Swath Check Lines Load check survey into MBMAX. Edit without angle limits. Beam Angle TestStart the Beam Angle Test from the Tools menu. Final reference surface is quite flat. Depth range = 51’ to 52’.
10/11/20145 Creating your Reference Matrix Choose Cell Sizes that will Maximize your Full Data Set 10/11/20145 HYPACK® Multibeam Training Seminar
10/11/20146 Points Per Per _Cell _ 123+ Reference Matrix with 1’ x1’ Cells Reference Matrix with 1.5’ x1.5’ Cells Points per Cell Statistics 10/11/20146 HYPACK® Multibeam Training Seminar
10/11/ HYPACK® Multibeam Training Seminar
10/11/20148 Beam Angle Test Difference Statistics: Reference Minus Check. Comparison Tab is Overall Result X Axis is beam angle. Y Axis is depth difference. X’s show bias. O’s show repeatability. Maximum difference at 95% confidence. Details Tab is Result at Specific Angle Histogram is the distribution. Max Outlier = Max difference. Mean Difference shows bias between reference and the check lines. 95% confidence = 2 * Standard Deviation. 10/11/20148 HYPACK® Multibeam Training Seminar
Case Study: S/V Dobrin RequirementDobrin Result Max Outlier< 1.0 Ft0.5 Ft Mean Difference< 0.1 Ft0.0 Ft 95% Confidence< 1.0 Ft0.3 Ft 10/11/2014HYPACK® Multibeam Training Seminar9 USACE EM manual Successful Beam Angle TestSuccessful Beam Angle Test: Results for NY District S/V Dobrin fall within USACE performance standards for survey data collected in 40’ on a hard bottom. Results give system repeatability. Other methods must be included to find system accuracy; bar check, lead line comparison, etc.
Performance Test in Action 10/11/2014HYPACK® Multibeam Training Seminar10
10/11/2014HYPACK® Multibeam Training Seminar11 Interferometric Multibeam Example Performance Test Result
10/11/2014HYPACK® Multibeam Training Seminar12 Example Performance Test Result Beamforming Multibeam
10/11/ /11/ HYPACK® Multibeam Training Seminar SINGLE BEAM VS. MULTIBEAM HYPACK ® MULTIBEAM COURSE
Single Beam Test 10/11/2014HYPACK® Multibeam Training Seminar14 Single beam check lines over the reference surface will give us a multibeam vs. single beam comparison. Do single beam and multibeam soundings match up? They better!
Steps to the Single Beam Test 10/11/2014HYPACK® Multibeam Training Seminar15 Single Beam Editor Export MBMAX Check Lines: Raw Data Edited All Format XYZ Format Reference.xyz Reference.mtx Single Beam Test Launch Single Beam Test from Tools menu (MBMAX Phase 3)
Single Beam Test 16 Running the Test Select Single Beam Test from the Tools menu in MBMAX. Open the Reference XYZ file. Results Once again using difference statistics = Reference minus Check. Histogram shows the distribution and bias. Max Outlier = Max Difference. Mean Difference = Bias. This is the main point of the test! Standard Deviation (Sigma): Spread of the difference distribution. 95% Confidence = 2*Sigma. 95% of the differences fall within 2*Sigma. Not bad. Bias less than 0.1 foot! 10/11/2014HYPACK® Multibeam Training Seminar16
Sample: Single Beam Test 10/11/2014HYPACK® Multibeam Training Seminar17