Day 24: Troubleshooting Data Acquisition – Masterpiece Edition | River Warrior

⚠️ DAY 24: TROUBLESHOOTING DATA ACQUISITION

Masterpiece Edition – Identify, Diagnose, and Fix Real‑Time Survey Problems

Instructor: Engr. Rokib Hossain | River Warrior Academy

🏠 Course Homepage

GNSS RTK: FIX

Motion Sensor: OK

SVP Age: 3.2 hrs (caution)

Sonar: Active

Side Scan: Noise detected

1. Why Troubleshooting Skills Matter

No matter how well you plan, hydrographic surveys encounter problems: GNSS loses fix, motion sensor drifts, SVP is outdated, side scan shows excessive noise. The difference between a good hydrographer and a great one is the ability to diagnose and fix issues in real time, without aborting the entire survey.

This day provides a systematic approach to troubleshooting the most common data acquisition failures. Use the flowcharts and checklists to quickly restore data quality and avoid costly re‑mobilisation.

🧠 Golden Rule: Stop logging immediately when you detect an anomaly. Fix the root cause, then re‑run the affected line. Never try to “patch” bad data in post‑processing – it will always fail IHO standards.

2. GNSS / RTK Fix Loss

Symptoms: RTK status drops from “FIX” to “FLOAT” or “DGPS”. PDOP spikes above 4. Horizontal/vertical jumps visible on navigation screen.

Possible causes & fixes:

Base station too far: If baseline >20 km, move base closer or switch to NTRIP. Review Day 8: RTK vs PPK
Radio interference: Change radio channel, increase antenna height, or use cellular NTRIP.
Poor satellite geometry: Wait 5‑10 minutes or change survey direction. Check almanac for constellation health.
Multipath (near buildings, cliffs): Move vessel slightly or use choke‑ring antenna.

3. Motion Sensor (IMU) Errors

Symptoms: Unrealistic heave values (>1 m), roll/pitch exceeding 10° in calm seas, depth spikes correlated with vessel motion.

IMU not aligned with vessel axes: Re‑run patch test (Days 13‑14). Check alignment angles.
Heave filter settings too aggressive: Reset to manufacturer defaults (30‑60 seconds).
Vibration from engine: Use rubber dampers; move IMU away from engine room.
GNSS‑aided IMU lost RTK: Wait for RTK to return; IMU drifts if RTK absent >1 minute.

4. Sound Velocity Profile (SVP) Issues

Symptoms: Outer beams of MBES show “smile” or “frown” artifacts. Depth difference between port and starboard. Cross‑line mismatch >0.2 m.

SVP too old (>4 hours): Cast a new SVP. In estuaries, every 2 hours.
Incorrect surface sound velocity: Clean transducer face, verify calibration.
Ray‑tracing disabled: Ensure “Apply SVP” is turned on in software.
Wrong SVP file: Verify that the file matches date/time and position.

5. Sonar (MBES/SBES) Problems

Symptoms: No bottom detection, erratic depths, excessive noise, missing outer beams.

No bottom detection: Check transducer connection. Increase range/power. Verify sound velocity.
Erratic depths (spikes): Reduce gain, enable TVG. Check for bubbles or propeller noise. Day 7: SBES vs MBES
Missing outer beams (MBES): Increase power or reduce swath angle. Verify SVP and roll/pitch calibration.
Interference: Offset ping rates between multiple sonars.

6. Side Scan Sonar Noise & Dropouts

Symptoms: Waterfall display shows vertical stripes, low contrast, missing strips.

Propeller noise: Deploy towfish farther (3‑5× vessel length). Use vibration dampener.
Gain too high/low: Adjust TVG and overall gain for uniform background.
Cable damage: Inspect tow cable – replace if intermittent.
Layback error: Re‑measure layback and update software offsets. Day 23: Side Scan

7. Data Logging & Storage Failures

Disk full: Stop logging, delete old backups, or switch external drive. Always carry spare SSD.
File corruption: Use NTFS, enable checksum verification, avoid unplugging drives while writing.
Software crash: Check auto‑recovery files (.tmp, .rec).
Backup failure: Follow 3‑2‑1 rule. Day 20: Data Logging Deep Dive

8. Field Troubleshooting Checklist

✅ GNSS: RTK fix every 5 min. Lost? → base radio, baseline, sky view.
✅ Motion sensor: Verify heave, roll, pitch against sea state. Abnormal → restart IMU, check mounting.
✅ SVP: Cast every 2‑4 hours. If depth errors appear → re‑cast.
✅ Sonar: Monitor bottom detection, reduce speed if bubbles. Check transducer face.
✅ Side scan: Observe waterfall, adjust gain/range. Listen for cable strumming.
✅ Data logging: Verify file creation and size. Check free disk space hourly.
✅ Backup: Copy raw data after each line. End of day: third drive off‑vessel.

9. External Resources & Tools

Organization / Tool	Resource Category	Link
NOAA Field Procedures Manual	Troubleshooting (Chapter 8)	NOAA PDF
Hypack Troubleshooting Guide	Common error codes and fixes	Hypack Support
Teledyne RESON Support	SeaBat diagnostic logs	Teledyne RESON
QPS QINSy Knowledge Base	Sensor error messages	QPS QINSy
SonarWiz Forum	Side scan troubleshooting	SonarWiz Forum

10. SVP Correction Calculator (Interactive)

🔧 Correct measured depth using actual sound velocity

Measured depth (m):

Sound velocity used (m/s):

Actual sound velocity (m/s):

Corrected depth = --.-- m

Formula: Actual Depth = Measured Depth × (Actual SV / Used SV)

11. Frequently Asked Questions

🔹 My RTK fix is intermittent. Should I continue surveying?

No. Stop immediately. Log raw data for PPK. If you continue, you will have decimetre‑level errors. Review Day 8.

🔹 How do I know if my SVP is bad?

Sail over a flat area and examine MBES outer beams. If they show systematic smile or frown, re‑cast SVP. Day 6: SVP

🔹 Side scan waterfall is very dark on one side – what to do?

Check towfish alignment – it may be tilted. Also verify cable is not twisted. Adjust gain balance. Day 23

🔹 My MBES shows no bottom detection in shallow water (<2 m).

Reduce range to minimum, use “very shallow water” mode, slow down to <3 knots. Day 7

🔹 How to use the SVP calculator above?

Enter the depth measured with an assumed sound velocity (e.g., 1500 m/s), then enter the actual SV from your cast. The calculator gives corrected depth. Essential for quick field checks.

12. Action Items & Next Steps

📌 Create a personal troubleshooting cheat sheet for your most common equipment.
📌 Simulate a “lost RTK fix” scenario in your acquisition software and practice switching to raw logging.
📌 Use the SVP calculator with a real profile from your last survey.
📌 Proceed to Day 25: Module 3 Quiz.

13. Post‑Verification Checklist

✅ Canonical URL & meta tags correct.
✅ Schema includes isAccessibleForFree: true.
✅ Table markup clean (no invalid characters).
✅ Print CSS hides buttons and calculator.
✅ Internal links point to existing Days (6,7,8,20,23,25).
✅ Health dashboard and calculator work.

⚠️ Day 24: Troubleshooting Common Acquisition Errors