Roman A PLSC2007

Information about Roman A PLSC2007

Published on February 11, 2008

Author: Calvin1

Source: authorstream.com

Content

Datums, Heights and Geodesy Central Chapter of the Professional Land Surveyors of Colorado 2007 Annual Meeting :  Datums, Heights and Geodesy Central Chapter of the Professional Land Surveyors of Colorado 2007 Annual Meeting Daniel R. Roman National Geodetic Survey National Oceanic and Atmospheric Administration Outline for the talks:  Outline for the talks Three 40-minute sessions: Datums and Definitions Geoid Surfaces and Theory Datums Shifts and Geoid Height Models Sessions separated by 30 minute breaks 30-60 minute Q&A period at the end Datums and Definitions:  Datums and Definitions Session A of Datums, Heights and Geodesy Presented by Daniel R. Roman, Ph.D. Of the National Geodetic Survey Principal Vertical Datums in the U.S.A.:  Principal Vertical Datums in the U.S.A. North American Vertical Datum of 1988 (NAVD 88) Principal vertical datum for CONUS/Alaska Helmert Orthometric Heights National Geodetic Vertical Datum of 1929 (NGVD 29) Superseded by NAVD 88 Normal Orthometric Heights International Great Lakes Datum of 1985 (IGLD 85) Primarily of concern on the Great Lakes Earth Gravity Model of 1996 (EGM96) Global reference model from NGA (aka NIMA aka DMA) Tied to a lot of products such as SRTM DEM’s Soon to be superseded by EGM07, which will use GRACE data Definitions: GEOIDS versus GEOID HEIGHTS:  Definitions: GEOIDS versus GEOID HEIGHTS “The equipotential surface of the Earth’s gravity field which best fits, in the least squares sense, (global) mean sea level.”* Can’t see the surface or measure it directly. Can be modeled from gravity data as they are mathematically related. Note that the geoid is a vertical datum surface. A geoid height is the ellipsoidal height from an ellipsoidal datum to a geoid. Hence, geoid height models are directly tied to the geoid and ellipsoid that define them (i.e., geoid height models are not interchangeable). *Definition from the Geodetic Glossary, September 1986 Ellipsoid, Geoid, and Orthometric Heights:  H H = Orthometric Height (NAVD 88) H = h - N TOPOGRAPHIC SURFACE h = Ellipsoidal Height (NAD 83) N = Geoid Height (GEOID 03) Ellipsoid, Geoid, and Orthometric Heights A B Slide7:  All Heights Based on Geopotential Number (CP) The geopotential number is the potential energy difference between two points g = local gravity WO = potential at datum (geoid) WP = potential at point Why use Geopotential Number? - because if the GPN for two points are equal they are at the same potential and water will not flow between them Heights Based on Geopotential Number (C):  Heights Based on Geopotential Number (C) Normal Height (NGVD 29) H* = C /   = Average normal gravity along plumb line Dynamic Height (IGLD 55, 85) Hdyn = C / 45 45 = Normal gravity at 45° latitude Orthometric Height H = C / g g = Average gravity along the plumb line Helmert Height (NAVD 88) H = C / (g + 0.0424 H0) g = Surface gravity measurement (mgals) National Geodetic Vertical Datum 1929 (NGVD 29):  National Geodetic Vertical Datum 1929 (NGVD 29) Defined by heights of 26 tidal stations in U.S. and Canada Tide gages were connected to the network by leveling from tide gage staffs to bench marks Water-level transfers used to connect leveling across Great Lakes Normal Orthometric Heights: H* = C /  C = model (“normal”) geopotential number  = from normal gravity formula H* = 0 level is NOT a level surface Slide10:  First-Order Leveling Network NGVD 29 North American Vertical Datum 1988 (NAVD 88):  North American Vertical Datum 1988 (NAVD 88) Defined by one height (Father Point/Rimouski) Water-level transfers connect leveling across Great Lakes Adjustment performed in Geopotential Numbers Helmert Orthometric Heights: H = C / (g + 0.0424 H0) C = geopotential number g = surface gravity measurement (mgals) H0 = approximate orthometric height (km) H = 0 level is nearly a level surface H = 0 level is biased relative to global mean sea level Slide12:  Vertical Control Network NAVD 88 NGVD 29 Versus NAVD 88:  NGVD 29 Versus NAVD 88 Datum Considerations: NGVD 29 NAVD 88 Defining Height(s) 26 Local MSL 1 Local MSL Tidal Epoch Various 1960-78 (18.6 years) Treatment of Leveling Data: Gravity Correction Ortho Correction Geopotential Nos. (normal gravity) (observed gravity) Other Corrections Level, Rod, Temp. Level, Rod, Astro, Temp, Magnetic, and Refraction Adjustments Considerations: Method Least-squares Least-squares Technique Condition Eq. Observation Eq. Units of Measure Meters Geopotential Units Observation Type Links Between Height Differences Junction Points Between Adjacent BMs NGVD 29 Versus NAVD 88 (continued):  NGVD 29 Versus NAVD 88 (continued) Adjustments Statistics : NGVD 29 NAVD 88 No. of Bench Marks 100,000 (est) 450,000 (US only) Km of Leveling Data 75,159 (US) 1,001,500 31,565 (Canada) Published Information: Orthometric Height Type Normal Helmert Orthometric Height Units Meters Meters Gravity Value Normal “Actual” Slide15:  Level Surfaces and Orthometric Heights Level Surfaces Plumb Line “Geoid” PO P Level Surface = Equipotential Surface (W) H (Orthometric Height) = Distance along plumb line (PO to P) Earth’s Surface Ocean Mean Sea Level Geopotential Number (CP) = WP -WO WO WP Slide16:  Leveled Height Differences A C B Topography Slide17:  Equipotential Surfaces HC HA Reference Surface (Geoid) HAC  hAB + hBC Observed difference in orthometric height, H, depends on the leveling route. A C B Topography  hAB  h = local leveled differences Leveled Height vs. Orthometric Height =  hBC H = relative orthometric heights Principal Reference Ellipsoids in the U.S.A:  Principal Reference Ellipsoids in the U.S.A North American Datum of 1983 (NAD 83) Uses a GRS-80 ellipsoid shell (the standard) Coordinates compatible with GPS observations System hasn’t changed over time North American Datum of 1927 (NAD 27) Regional ellipsoid – not global! Superseded by NAD 83 World Geodetic System of 1984 Developed by NGA (aka NIMA aka DMA) Several versions since first introduced based on GPS week Very similar to the evolution of the ITRF models Essentially the same GRS-80 shell but a different geocenter Offset is nearly 2.2 meters from NAD 83 NAD27, NAD83, WGS84:  NAD27 WGS84 and NAD83 share the GRS80 ellipsoid but the origin differs by about 2m NAD27 uses the Clark spheroid of 1866, the origin is 236 m from WGS84 NAD83 GEOID Earth Mass Center Approximately 236 meters Approximately 2 meters NAD27, NAD83, WGS84 WGS84 The Ellipsoid:  The Ellipsoid N b a S f = a-b = Flattening a a = 6,378,137.000 meters (semi-major axis) 1/f = 298.25722210088 (flattening) Geodetic Reference System 1980 a = Semi major axis b = Semi minor axis b = 6,356,752.3141403 m (semi-minor axis) Slide21:  Global Positioning System Slide22:  Z Y X -Z -X -Y Zero Meridian Mean Equatorial Plane Slide23:  Earth-Centered-Earth-Fixed Coordinates Z Axis X Axis Y Axis (X,Y,Z) Earth’s Surface Zero Meridian Mean Equatorial Plane P Origin (0,0,0) Center of Mass X Y Z Conventional Terrestrial Pole Slide24:  GPS - Derived Ellipsoid Heights   Z Axis X Axis Y Axis (X,Y,Z) = P (,,h) h Earth’s Surface Zero Meridian Mean Equatorial Plane Reference Ellipsoid P Tidal Datums:  Tidal Datums Heights Measured Above Local Mean Sea Level National Tidal Datum epoch; 19 year series Encompasses all significant tidal periods including 18.6 year period for regression of Moon’s nodes Averages out nearly all meteorological, hydrological, and oceanographic variability Leveling is used to determine relationship between bench marks and tidal gauges Slide26:  AL, AK, CA, CT, FL, GA, LA, MD, MS, NJ, NY, NC, OR, RI, SC, WA Privately Owned Uplands State Owned Tidelands Territorial Seas State Submerged Lands Contiguous Zone Exclusive Economic Zone Federal Submerged Lands High Seas Privately Owned State Owned TX 3 n. mi. 12 n. mi. 200 n. mi. Privately Owned State Owned DE, MA, ME, NH, PA, VA MHHW MHW MLLW Importance of Shoreline Chart Datum GGM02S (GRACE)/GPS vs. NAVD 88:  GGM02S (GRACE)/GPS vs. NAVD 88 QUESTIONS?:  QUESTIONS? Geoid Research Team: Dr. Daniel R. Roman, research geodesist [email protected] Dr. Yan Ming Wang, research geodesist [email protected] Jarir Saleh, ERT contractor, gravity database analysis William Waickman, programming & database access Ajit Sing, Datum Transformation Expert Website: http://www.ngs.noaa.gov/GEOID/ Phone: 301-713-3202

Related presentations


Other presentations created by Calvin1

endangered animals powerpoint1
15. 01. 2008
0 views

endangered animals powerpoint1

june speke newsletter
16. 04. 2008
0 views

june speke newsletter

Montreal Managing Goods
03. 04. 2008
0 views

Montreal Managing Goods

17a pshebnisky canadian
21. 03. 2008
0 views

17a pshebnisky canadian

The Disney Recreation Experience
19. 03. 2008
0 views

The Disney Recreation Experience

viral encephalitis
15. 03. 2008
0 views

viral encephalitis

ukraine report 2 2008
11. 03. 2008
0 views

ukraine report 2 2008

2 Pilot Ergo Hearing
05. 03. 2008
0 views

2 Pilot Ergo Hearing

CIERA SchChange New York 072307
28. 02. 2008
0 views

CIERA SchChange New York 072307

CEOP 2005 Diurnal Cycles
25. 02. 2008
0 views

CEOP 2005 Diurnal Cycles

Mother to Son
16. 01. 2008
0 views

Mother to Son

recycle
09. 01. 2008
0 views

recycle

VUS 9
11. 01. 2008
0 views

VUS 9

TASMSept07
14. 01. 2008
0 views

TASMSept07

Class10 Beatitudes
15. 01. 2008
0 views

Class10 Beatitudes

Pamies wed ballroomGS1
16. 01. 2008
0 views

Pamies wed ballroomGS1

renner presentation
17. 01. 2008
0 views

renner presentation

Venus Fly Traps
22. 01. 2008
0 views

Venus Fly Traps

Med Basics OR
04. 02. 2008
0 views

Med Basics OR

Wedding At Cana
05. 02. 2008
0 views

Wedding At Cana

NGB Presentation March 05
07. 02. 2008
0 views

NGB Presentation March 05

Cotton Farming
25. 01. 2008
0 views

Cotton Farming

12601154 Visuals
15. 01. 2008
0 views

12601154 Visuals

EFW2006 Pedersen Plasma density
16. 01. 2008
0 views

EFW2006 Pedersen Plasma density

2006 clarecollege
23. 01. 2008
0 views

2006 clarecollege

0711 RFuller CCN Nov07
05. 02. 2008
0 views

0711 RFuller CCN Nov07

CCA P Powerpoint 04131407
18. 02. 2008
0 views

CCA P Powerpoint 04131407

non status hourly training
04. 02. 2008
0 views

non status hourly training