TESTING OF KGPS FOR TIDE APPLICATION TO HYDROGRAPHIC

SURVEYS BY THE NAVAL OCEANOGRAPHIC OFFICE

Objectives of the Test Plan are to determine:

- Accuracy

- Methods

- Procedures

LSU-1 Tide Gage 7 N.M.

ACOE Tide gage 10 N.M.

Gulfport Base Station

KGPS Buoy

Tide gage

GULFPORTBase Station

• Test Plan:

- Establish an offshore tide gage

- Measure the distance between spheroid and

chart datum at the gage

- Place a KGPS buoy alongside the tide gage

- Run survey lines near the buoy in kinematic

mode to correct for tides (Real time and post-processing)

- Compute buoy chart datum distance from spheroid

and compare to tide gage distance

- Compare kinematic tide corrections to tide gage corrections

•

KGPS Buoy built by Planning Systems Incorporated

BUOY CAPABILITIESBuoy Dimensions: Hull diameter 6.25 feet Overall height: 17 feet Weight: 900 lbs

Sensors: 3-axis Acceleration 3-axis Magnetometer Vertical Reference Hull depth pressure sensor GPS- Novatel OEM4 L1/L2 with GPS600 antenna CPU and 20 GB HDD Power: Four solar panels Sealed batteries

Warning system: Flashing obstruction light Radar reflector

WGS-84 Ellipsoid

Buoy phase center

Water surface

Observed MSL

Chart Datum

b

C + accel. & tilt corr.

Zoo - s

t

a

sZoo/ncorr.)tilt & accel.c(ba

.

s = seasonal changen= no.of obs.

Zoo = distance of long term MSL to chart datum

C = vertical distance from phase center to water surface while stable

ERROR SOURCES:

- Squat-settlement will have to be removed from GPS height results to make a direct comparison with the tide gage.

- Measured vertical distance at offshore gage from the GPS antenna to zero of gage not easily measured.

- Receiver noise, multipath and distance from base station result in errors in GPS

- Error occurs in datum transfer of chart datum

- Acceleration and tilt errors occur at the buoy and vessel

- Other systematic and random errors are possible