NAVO/PSI Buoy. Equipped with RTK GPS Rover Receiver, Buoy attitude and motion sensors, data acquisition system, and telemetry system.

Reference StationEquipped with RTK GPS Reference Receiver, telemetry transmitter/receiver system, PC based data storage, Control software to interact with buoy system.

2-way data communications link.RTK for 2-cm accuracy requires path length of10-km (6.2 miles) or less.

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Aug 2002

Buoy based RTK GPS system receives RTK corrections, processes data. GPS RTK data stored aboard buoy. Buoy also processes and stores GPS antenna x,y,z motion. Processing determines water level after accounting for buoy motion in the seaway.

Reference station, shore or off-shore structure based, provides RTK corrections to buoy GPS system via high power data link. When needed data link send commands to buoy or downloads data files (off-line).

RTK data link requires at least 9600 bps is needed.

Line of sight requires approximately 10’ buoy antenna height and 15’ reference station height.

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Jan 2001

RTK & data telemetry antenna

GPS L1/L2 Receiver antenna

Telemetry Radio & Solar Power Controller

Buoy Attitude Sensors (magnetometer, accelerometer, vertical reference, pressure)

RTK L1/L2 Receiver

Pentium CPU, 20GB HDD, EtherNet, RS-232 Ports, Digital Ports, PC-104 interface for A/D

Electronics and BatteryRack

60 Watt solar panels (4 @ 20° angle)

4 Sealed Pressure Regulated Secondary Batteries

Buoy Dimensions

12-feet waterline to antenna top

5-feet draft from waterline

1200 lb total weight

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Aug 2002

RTK GPS System Description

Reference Station and Buoy GPS – NovAtel OEM-4

L1/L2, 12 channel, RTK differential capable

6 – 18 VDC, 2.7 Watts

-40°C to +85°C operating temperature

95% non-condensing humidity

Reference Station GPS Antenna - NovAtel Model 503

Dual frequency antenna and choke ring with radome

Buoy GPS Antenna - NovAtel Model 600

Dual frequency antenna

Radio Modem - FreeWave® DGR-115R

900MHz, Spread Spectrum, 9.50-014.0 VDC

Base Station Telemetry Antenna - Cushcraft PC9013N Yagi

Buoy Telemetry Antenna - Cushcraft S8964B Omni Antenna

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Aug 2002

Attitude Measurement System

Accelerometers - Crossbow Technologies CXL02LF3

3-axis, ± 2 g, 1-V/g (calibrated sensitivity & offset)

8 – 30 VDC, with integrated 5 VDC regulator, 12-mA

-40°C to +85°C operating temperature

Magnetometers - Watson Industries, Inc., FGM-301

3-axis, ± 70,000 nT, 20nT/mV

6 – 15 VDC, 30mA

-50 °C to +80°C operating temperature

Vertical Reference - Watson Industries, Inc. ADS-C232-1A

Dual axis integrated sensor measuring tilt

x/y Displacement & x/y angular rate

± 15 VDC, 60mA, -20 °C to +50°C operating temp.

Pressure Sensor - SenSym Model SX30

0 – 30 psi

+12 VDC, -40 °C to +85°C operating temp.

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Aug 2002

Data Acquisition System

Single Board Computer - WinSystems® EBC-TXPlus, 256MB RAM, 20GB HDD

166MHz Pentium w/ EIDE, Ethernet, Video, PC-104

+5 VDC, with ± 12 VDC for PC-104

-40°C to +85°C operating temperature

Analog-to-Digital Converter - WinSystems® PCM-A/D-12

3-axis, ± 70,000 nT, 20nT/mV

+5 VDC, 200mA w/installed DC/DC Converter

-40 °C to +80°C operating temperature

Watch Dog Timer - Parallax Basic Stamp II

Programmable to cause full power reset

Development System - WinSystems® SDK2-EBX-104-D

Software - ANSI C using MSDOS 6.22

Interrupt driven data acquisition sync’d to GPS

© Planning Systems IncorporatedEngineering Center, Aug 2002

Buoy Power Budget

Power Supply Required: 4 faces with 1 SX65 (65Watt) Solar Panels. The following tables show that the buoy power system should operate in the average conditions for the northern Gulf of Mexico in September. Previous experience with the buoy showed that the solar power system was able to recharge the secondary batteries and maintain the load without any interruptions. Buoy uses a Morningstar ProStar-30 Solar Controller to efficiently control battery conditioning during deployment.

Power Demand (Ah/Day)RTK GPS Receiver 5.4

RTK Receiver/transmitter 4.8

HDD 0.2

PCU, PC-104 A/D 43.6

Attitude Sensors 0.9

Est’ed Daily power requirement 54.9 Ah/Day

Power Supply (Ah/Day)Worse case simulation. 4 faces (SW, SE, NW, NE; using Siemans SX60 panels, 1 per face.

September, Gulf of Mexico

Face Ah/Day

S 16.45

E 14.27

W 14.27

N 10.97

Total available 55.96 Ah/day

RTK GPS Water-Level Measurement Buoy System

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Aug 2002

Buoy Rover System Architecture

+12VDC

+5VDC

+/-15VDC+/-12VDC

RadioModem

WinSysCPU

NovAtelOEMRT2

GPS

Com1

Com1

Null Modem

Com

Com2

Straight Cable

PC104A/D

20GBHDD

EIDE

3-axisAccelerometer

3-axisMagnetometer

VerticalReference

HouseKeeping

4 facesSX-60

Solar Panels

4 SchottkyBlocking Diodes

90SQ040

ProStar 30Solar Controller

PC104 DC/DCConverter

DC/DCConverter

PressureSensor (Depth)

WatchdogTimer

PowerRelay

RTK GPS Water-Level Measurement Buoy System

© Planning Systems IncorporatedEngineering Center, Aug 2002

Shore-side GPS Reference Station Architecture

RadioModem

Com 1Straight Cable

WinSysCPU

Com2

Com1

20GBHDD

EIDE

RTK GPSReference

Station

Com

2

Nul

l M

odem

12VDCConverter

120VAC Mains