HYSWEEP® PATCH TESTING

Calibration of a Multibeam System HYSWEEP® Calibration of a Multibeam System Running a Patch Test on Single and Dual Head Multibeam Systems Pat asked to include USACE regs. for patch testing. I don’t see them here. PROJECT: SAMPLE PATCH TEST SINGLE HEAD 4/23/2017 HYPACK® 2009 Training Seminar

Patch Testing a Multibeam System A Patch Test Determines Correction to roll mounting angle. Correction to pitch mounting angle. Correction to yaw mounting angle. GPS latency (time delay). Bad roll calibration resulting in a 6’ difference in the outside beams USACE Requirements for Patch Testing (EM1110-2-1003) Patch tests are performed after initial installation, and periodically thereafter if sensors are modified, to quantify any residual biases from the initial system alignment. HYPACK® 2009 Training Seminar 4/23/2017

Errors Relating to the Multibeam Roll: Sonar and MRU alignment relative to vertical. Can cause large depth errors at outer beams. Pitch: Can cause depth and position errors across the swath. Yaw: Sonar and Gyro alignment relative to boat frame. Can cause position errors. HYPACK® 2009 Training Seminar 4/23/2017

HYPACK® 2009 Training Seminar GPS Latency Error Latency: Delay between position fix and data arrival time. Can cause positional errors Error is independent of multibeam system. HYPACK® 2009 Training Seminar 4/23/2017

HYPACK® 2009 Training Seminar Patch Test Survey Roll: Line A-B - Reciprocal lines, flat bottom. Survey speed. Pitch: Line C-D Reciprocal lines, sloping bottom. Survey speed. Yaw: Lines C-D, E-F Offset lines, sloping bottom. Survey speed. Latency: Line C-D Same line and direction, differing speed, sloping bottom. Watch for settlement differences. Dual Head Different geometry to overlap port and starboard heads separately. Roll, pitch and yaw tests require 3 lines instead of 2. Some dual head systems in engineered mounting frames can be treated as single head. Nice graphic! Line separation? 1x depth at shallow end as you stated in another slide? 1½ x depth?—I thought that’s what Pat said. HYPACK® 2009 Training Seminar 4/23/2017

Survey Hints and Warnings Test in the deepest section of the survey area. Except for latency, run lines at your normal survey speed. Run each test twice to confirm results. Average multiple tests for final results. DGPS Warning: Make sure you have good GPS positioning. Slight position error lead to patch test errors. If HDOP is high, perhaps best to patch testing another time. Assuming 3’ DGPS shift in 40’ of water Latency Test: +/- 0.4 seconds. Pitch Test: +/- 4.4 degrees. Yaw Test: +/- 4.3 degrees. Nice graphic! Line separation? 1x depth at shallow end as you stated in another slide? 1½ x depth?—I thought that’s what Pat said. HYPACK® 2009 Training Seminar 4/23/2017 7 7

HYPACK® 2009 Training Seminar Patch Test Processing In MBMAX Load survey lines in pairs (the two pitch lines for example). Edit through to Area Based Editing. Auto cell size in Matrix Setup usually works well. Starting the Patch Test The patch test works against a cross section cut through the survey lines. Use Tools menu to automatically cut a section or, Use “Wrench” icon to manually cut the section. Added GPS latency also to HYPACK® Hardware. 4/23/2017 HYPACK® 2009 Training Seminar

HYPACK® 2009 Training Seminar How It Works Numerical Method The cross sections are calculated at various angle offsets. For example; pitch offset from -10 to 10 degrees at one degree steps. An error value is calculated at each offset. Error = average depth difference between cross sections. Minimum error is usually the correct offset. But not always. Added GPS latency also to HYPACK® Hardware. Good Fit Cross sections overlay well. Error is at the minimum point. Poor Fit Cross sections overlay poorly. Large error. 4/23/2017 HYPACK® 2009 Training Seminar 9 9

HYPACK® 2009 Training Seminar The Patch Test Window Select Test Pick the tab corresponding to the test you want to run. Results Read test results here. Select Sonar Head For dual head systems, select head 1 or 2 Error Graph X axis is angle or time adjustment. Y axis is the error; difference between cross sections. Cross Sections Red is the first line, green is the second. Added GPS latency also to HYPACK® Hardware. Override Select Next or Previous adjustment. Vertical Adjustment Moves the first line up or down if needed. 4/23/2017 HYPACK® 2009 Training Seminar 10 10

HYPACK® 2009 Training Seminar Roll Test Single Head Angle step of 0.1 degree. Can go to 0.05. Good overlap in cross sections. Good “U-Shaped” error curve. Dual Head Totally different result for each head. “Decent” sounds subjective…maybe “clear” , “clean” or “distinct”? HYPACK® 2009 Training Seminar 4/23/2017 11 11

HYPACK® 2009 Training Seminar Other Tests Pitch, Yaw, Latency Angle step of 1.0 degrees using DGPS for pitch and yaw. Better resolution if RTK. Time step of 0.1 second using DGPS for latency test. Better resolution if RTK. Order of Processing: Find the latency offset first Apply latency, then do the pitch test. Apply pitch, then do the roll test. Apply roll, then finish with the yaw test. “Decent” sounds subjective…maybe “clear” , “clean” or “distinct”? HYPACK® 2009 Training Seminar 4/23/2017 12 12

HYPACK® 2009 Training Seminar Results Some Error Curves Good. Bad. Should see a U-shaped error curve. Test Results (from the patch test window) Adjustment: Patch test change to initial offset. Initial Offset: Offset before patch test. From HYSWEEP® Hardware. Final Offset: Offset after patch test. To be included in average for update to HYSWEEP® Hardware. “Decent” sounds subjective…maybe “clear” , “clean” or “distinct”? HYPACK® 2009 Training Seminar 4/23/2017 13 13

HYPACK® 2009 Training Seminar Patch Test in Action Automatic Patch Test 4/23/2017 HYPACK® 2009 Training Seminar