• What do we do?

• How good are the results?

• How is it best used?

• Specific benefits of crowd sourcing

• What do we do?

Vessels logging data:GPS, depth, …

Processing on the internet

Output data sets

Online viewing

Loggers have freedata access

TeamSurv supports data logged from:• TeamSurv’s hardware data logger (supplied on free loan)• TeamSurv’s software logger• Many 3rd party ECDIS and other navigation systemsThe hardware logger is designed for user installation.

After installation, a calibration process is undergone:

Calibration Parameter Purpose

Depth sounder & GPS model info Correct for different base speed of sound values, and quirks in NMEA outputs

Transducer depth Obtain depth below waterline

GPS antenna/depth transducer offset Fix position at depth transducer

Ship dimensions Squat corrections (ships only)

Sounder calibration Validate transducer depth data

Designed for maximum ease of useand minimum intrusion on the crew

• Data logged from the vessel automatically whenever it is at sea• Logging can be switched off by the crew if desired• Minimum data logged: position, date/time, Course over Ground, depth

below transducer• Also used where available: heading, sea surface temperature• If a ship re-ballasts, new draughts also recorded by the crew• Data uploaded to the TeamSurv server at the convenience of the crew

Quality control:• Check records for completeness• Filter out position, time and depth glitches

Reducing individual tracks to chart datum by applying:• Transducer depth corrections – draught and squat• GPS antenna/depth transducer offset• Speed of sound correction• Tide correction using tide predictions and tide gauge data

Crowd sourced sensor measurements are inherently noisy:• GPS is less accurate than survey grade (95% < 5m RMS2 error)• Depth sounder is less accurate (~1 – 2% of depth)• Depth sounder is wider beam angle (6° - 9 °)• Calibration differences• No measure of vessel motions – but close to zero sum with

large data volumes• Speed of sound and tide corrections may be less accurate

To minimise the noise and to increase the self-consistency and accuracy of the data we need:• A high density of data• Data from multiple vessels• A statistical approach to data processing

A numbers game: more data more accuracy.A few tracks from “select” vessels will always give worse results

• Statistical synthesis of logged data

• Adaptive grid generated• Larger quantities of more

consistent data higher resolution grid

• Poor quality data discarded• Data quality parameter

associated with each grid cell

• Statistical synthesis of logged data

• Adaptive grid generated• Larger quantities of more

consistent data higher resolution grid

• Poor quality data discarded• Data quality parameter

associated with each grid cell

• How good are the results?

Multibeam data

TeamSurv data

Grid size

Depth differences

Strengths Weaknesses

Meets S-44 Order 2 in almost all cases, and Order 1b can be met when there is sufficient data in an area

Cannot achieve full bottom coverage

Data accuracy and resolution increases with time, as more data is acquired

Cannot do an instant survey – needs time to recruit vessels and build up sufficient data

Provides depth data for “where the boats go”

Cannot control the survey area except by careful vessel recruitment

Provides a continuous resurvey of the area, by time slicing the data

• How is it best used?

• Specific benefits of crowd sourcing