Upload
lucas-cameron
View
221
Download
0
Tags:
Embed Size (px)
Citation preview
GPS for NOAAHydrographic Surveying
CDR Gerd F. Glang & Jack L. Riley
National Ocean Service, NOAA
NOAA GNSS Workshop 2007
Introduction
• NOAA Charting
• NOAA Hydrographic Surveying
• GPS Positioning
• Vertical Datums
• Concluding Remarks
NOAA’s Charting Mission
• Safety of Navigation– Provide nautical charts and related hydrographic
information for safe navigation of maritime commerce
– Includes U.S. territorial waters and the U.S. Exclusive Economic Zone (EEZ)
– 3.4 million square nautical miles (snm) which extend 200 nautical miles offshore
• 500,000 snm Navigationally Significant Areas
• 43,000 snm Critical Areas (1994)
• High-quality charts depend on up-to-date, reliable hydrographic survey data
NHSP - Alaska
NOAA GNSS Workshop 2007
• NOAA Charting
• NOAA Hydrographic Surveying
• GPS Positioning
• Vertical Datums
• Concluding Remarks
Hydrographic Surveys
• Locate, Verify, Describe...– Features Below Mean High Water (MHW)
• Dangers-to-Navigation (DTONs)
– Aids to Navigation– MHW Shoreline
• Echosounder Bathymetry• Side Scan Sonar Imagery• Dive Investigations• Bottom Samples• Shoreline• Metadata
NOAA Survey Platforms
Equipment• GPS & Platform Attitude
– Applanix POS MV 320 v4
– Trimble DGPS, C-NAV WADGPS/PPP
• Multibeam Echosounders / Backscatter– Reson 8101, 8111, 8125, 8160, 7125
– Elac 1050 & 1180
– Simrad 1002, 3000
• Airborne laser (or lidar) bathymetry– Optech
– LADS
• Side Scan Sonar– Klein 3000 & 5000 Systems
• Phase Differencing (Interferometric) Sonars– Benthos C3D evaluation in AK during 2007
– Klein 5410
– Geoacoustics
• Autonomous Underwater Vehicle (AUV)– REMUS Hydroid w/ Kearfott T-16
• Vessel-based Laser Scanner for shoreline delineation– Experiment completed in VA during 2007
Measuring Bathymetry
Depth: uncertainty-weighted depth-most probable surface
Uncertainty: uncertainty-weighted uncertainty
Density: number of soundings that contributed to grid node
Standard Deviation: standard deviation of the soundings that contributed to grid node
Mean: “regular” average of the soundings that contributed to grid node
Shoal: shoalest of soundings contributing to grid node
Deep: deepest of soundings contributing to grid node
Gridded Bathymetry / Stats
Positioning Requirements
• Horizontal Accuracy (95%)– IHO S-44 Order 1: 5 meters + 5 percent of depth
• Vertical Accuracy (95%)– IHO S-44 Orders: ± [a2 + (b × depth)2]½
– Order 1: Depth ≤ 100 m a = 0.5 m, b = 1.3%– Order 2: Depth > 100 m a = 1.0 m, b = 2.3%– Special Order: a = 0.25 m, b = 0.75%
• Resolution– Complete Coverage – Detect Shoals:
• Depth ≤ 40 m 2-m x 2-m horizontal, 1-m vertical• Depth > 40 m 10% depth horizontal, 5% depth vertical
– Object Detection Coverage:• Depth ≤ 20 m 1 m3
• Depth > 20 m (5% depth)3
Vertical Components
seafloor
averagewater levelsea surface
tide
(( ))
static offset andvessel translation
& attitude
((
tide datum(zoned MLLW)
observed depth
charted depth
• Corrections from in-situ water level– High frequency (< 20s periods) via IMU heave– Medium frequency via dynamic draft model*– Low frequency via (> 3600s periods) zoned tides
Non-GPS Vertical Positioning
Tide Zoning
Chart Datum
tide datum(zoned MLLW)
seafloor
averagewater levelsea surface
charted depth
observed depth
tide
(( ))
static offset andvessel translation
& attitude
ITRF97 (1997.0)
NAD 83 (86)
NAVD 88
LMSL
geometrical relationship
GEOID99
spatialinterpolation of
tidal benchmarks tidal modeling ortidal benchmark
interpolation
((
ellipsoidal depth
antenna height
Surveying On The Ellipsoid
3-D position of vessel body related directly to a fixed coordinate system (ellipsoid datum)
No dynamic draft look-up table (biases)
Spectral combination of GPS height with inertial measurement unit (IMU) heave
Tidal zoning corrections replaced by vertical datum transformation
Real-time vs. post-processed solution
Surveying On The Ellipsoid
Survey Platform Ellipsoid Height
Time (sec) on J une 6
IMU
RP E
llipso
id H
eig
ht
(m)
Non-3D Positioning
50 cm pixels
3-D Positioning
50 cm pixels
Ad Hoc Datum Transform
Vertical Datum Transform
Ellipsoidal height MLLW depth is best achieved as a combination of stepwise transformations
ITRF97 (1997.0) NAD 83 (86)NAD 83 (86) NAVD 88
NAVD 88 LMSLLMSL MLLW
Each transformation step utilizes the best available theory and data
VDatum Transforms
NAD83 (NSRS)
NAVD 88 LMSL
MHHW
MHW
MTL
DTL
MLW
MLLW
WGS 84 (G873)
WGS 84 (G730)
WGS 84 (orig.)
ITRF97
ITRF94
ITRF96
ITRF93ITRF92ITRF91
ITRF90
ITRF89
ITRF88
SIO/MIT 92
NEOS 90
PNEOS 90
NGVD 29
GEOID99,GEOID03 TSS
(Topography of the Sea Surface)
ITRF2000 WGS 84 (G1150)
Datums Datums
3-D Datums Orthometric Tidal
Tidal Datum Fields
K2 Tide
2. Regional model computes elevation time series and tidal datums are computed based on analysis of these time series and adjusted to fit NOS tidal gauge datums
1. Global tide models provide boundary conditions to regional model
3. In bays TCARI is used to interpolate between differences in the regional model and the observed datums
VDatum Marine GridVDatum Marine GridModeled Tidal Datum Fields
Datum transformations also provided on regularly structured grids to VDatum:• Topography of the Sea Surface (NAVD88 – to – LMSL field): spatially
interpolated using benchmark data and a minimum curvature algorithm.
• VERTCON transformations between NAVD88 and NGVD29
• GEOID models
• NADCON horizontal datum transformations.
VDatum AvailableDec 2007Oct 2008
VDatum: West Coast
Puget Sound
North/CentralCalifornia
VDatum exists20072008
VDatum: Gulf Coast
VDatum AvailableOct 2007Oct 2008
Tampa Bay
Lake Charles
Port Fouchon
VDatum: East Coast
VDatum AvailableOct 2007Oct 2008Tidal Model Complete (waiting on geodetic ties)
North Carolina
New York BightDelaware Bay
VDatum: Great Lakes (Dec’07)
• Goal: All “surveying on the ellipsoid” by 2010• Implementation plan due 3rd QTR 2008
– PPK & PPK-aided inertial on the ship• Data acquisition & processing with QA• Vertical solution 100% availability within error budget• Maximize use of CORS
– VDatum to reduce soundings to MLLW (chart datum)– RTK? (need QA)– PPP when requirements allow (water depth)– GPS buoys to validate VDatum modeling– Augmentation & Hybrid GNSS?
Conclusion