1. HYSWEEP®
PATCH TESTING

2. 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

3. 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 (EM )
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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

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