Height Mod Overview

1
NOAAs National Geodetic Survey National Height
Modernization Program West Virginia GIS
Conference Charleston, West Virgina June 9-12,
2008 Renee Shields Height Modernization Manager
2
Overview

• NGS Mission and Height Modernization Overview
• Needs and Benefits of Accurate Heights
• Basic Geodesy - Heights
• Height Modernization in Kentucky
• NGS Roles and Responsibilities

3
Whats a Geodesist?
4
Whats a Geodesist?
5
Whats a Geodesist?
6
Mission of NGS

• To define, maintain and provide access to the
  National Spatial Reference System to meet our
  nations economic, social, and environmental needs

http//geodesy.noaa.gov/INFO/ngs_tenyearplan.pdf
7
From the NGS 10-Year Plan

• Define the NSRS
• The NSRS must be more accurate than all
  activities which build upon it, while still being
  practicably achievable.
• Maintain the NSRS
• NGS must track all of the temporal changes to
  the defining points of the NSRS in such a way as
  to always maintain the accuracy in the NSRS
  definition.
• Provide Access to the NSRS
• NGS must develop and maintain guidelines for
  users to access the NSRS at a variety of
  accuracies.
• NGS will publish all coordinates of defining
  points of the NSRS with an epoch tag and will
  furthermore publish velocities relative to that
  epoch-tagged set of coordinates

http//geodesy.noaa.gov/INFO/ngs_tenyearplan.pdf
8
Mission The NSRS is

• The official national coordinate system of the
  U.S. federal government which includes
• Geodetic latitude, longitude and height
• Scale, gravity, and orientation
• How these values change with time
• Components include
• National and Cooperative CORS
• Network of passive monuments
• Official national shoreline
• Precise orbits of GNSS satellites used to define
  NSRS
• Models and tools to describe how all of these
  quantities change over time.

9
Height Modernization Objective
NSRS
NSRS

NAVD88
GEODETIC CONTROL
10
Height Modernization is

• the establishment of accurate, reliable heights
  using GNSS technology in conjunction with
  traditional leveling, gravity, and modern remote
  sensing information.

11
The Roots of Height Modernization

• In 1994 - First meeting held in Sacramento, CA
• Some heights in CA in error by more than a meter
• GPS could be immediately used to meet some of
  Californias requirements
• Necessary for the implementation of NAVD 88
• In 1998, 1.0 M was added to NGS budget to
  perform Height Modernization Study

12
The Roots of Height Modernization

• In 2000, 500K added to NGS budget for Height
  Modernization planning
• In 2001, 2.25M added to NGS budget
• to implement Height Modernization in NC
• to support the California Spatial Reference
  Center (CSRC)
• to support NGS related Height Modernization
  activities
• Also in 2001, NOAA is directed to work with LA
  and WI to assess their requirements for Height
  Modernization

13
Height Modernization Appropriations (FY01-FY08)
Fiscal Year Appropriations States
FY 2001 2.25 M CA, NC
FY 2002 3.75 M CA, NC, LA, WI
FY 2003 3.75 M CA, NC, LA, WI, MS
FY 2004 9.0 M CA, NC, LA, WI, MS, AL, WA, SC
FY 2005 9.6 M CA, NC, LA, WI, MS, AL, WA, TX, KY
FY 2006 9.9 M CA, NC, WI, MS, AL, SC, TX, KY, AZ
FY 2007 9.9 M without direction
FY 2008 4.995 M 1.152 M Line AL, KY, IL
14
FY07 Height Modernization - Recipients
CA Scripps Institution of Oceanography (CSRC)
NC North Carolina Department of Environmental and Natural Resources (and North Carolina AT State University)
LA Louisiana State University (LSRC)
WI Wisconsin Department of Transportation
SC South Carolina Geodetic Survey
AL Alabama Department of Revenue
MS University of Southern Mississippi
WA Washington State Department of Natural Resources (SRCW)
TX Texas AM University, Corpus Christi (TSRC)
KY Morehead State University
AZ Arizona State Land Development (ASRC)
IL Illinois State Geological Survey
15
Participating and Interested States
?
?
?
?
?
16
Height Matters
Image credit AP Photo/Rick Bowmer
17
Measure, Monitor, Model - Crustal Motion/
Subsidence/Isostatic Rebound /Seasonal changes
West Coast Crustal Motion CA, WA
PA147 - PennDOT
Gulf Coast Subsidence LA, MS Localized
Subsidence AZ, NC
18
Measure, Monitor, Model ..
Water Management Water Levels
Seasonal Subsidence - TX
USM
Great Lakes region uplift - WI
19
Flooding river overflow, coastal, storm surge,
flash flood

• FEMA Map Modernization
  Program
• Flood Insurance Rate Maps
• Elevation Certificates
• FEMA Cooperative Technical States, e.g. NC

• Determining High Water Marks
• Evacuation Route Surveys
• Damage Mitigation

20
Water Resource Management

• Dam Safety
• Water resources
• Relating tidal and geodetic datums
• Ship transport underwater/overhead clearance

Folsom dam
Novi Special WT, MI
21

• Transportation
• Mapping and Charting
• Construction, Engineering
• Recover decimated control networks

22
DEMs, Geoid modeling
23
New and Non-traditional Applications

• Geographic Information Systems (GIS)
• Precision Farming
• Fleet Management

24
Local Issues
How can Height Modernization help?
25
How to achieve accurate heights

• Orthometric Heights
• Leveling
• Ellipsoid Heights
• GNSS
• Geoid Heights
• Modeled from Gravity

26
Traditional Height Determination Differential
Leveling NAVD88
27
NAVD88 Heights - Conventional Leveling

28
Problems with traditional leveling

• Leveling the country can not be done again
• Too costly in time and money
• Leveling yields cross-country error build-up
  problems in the mountains
• Leveling requires leaving behind passive marks
• Bulldozers and crustal motion do their worst

29
Can we get accurate heights with GNSS?
30
Guidelines
Available On-Line at the NGS Web
Site www.ngs.noaa.gov/PUBS_LIB/pub_index.html
31
GPS Ellipsoid Height Hierarchy
32
Main requirements for 2-cm standards using GNSS
surveying Local network

• Geodetic (DF)-grade equipment, with FIXED height
  poles for antenna placement
• Every baseline occupied twice different days /
  different (gt3 hrs) time
• Vertical component of duplicate baselines must
  agree to 2 cm, or be repeated
• Min. 30 minutes under ideal conditions--
  absolutely clear sky, no humidity highly
  recommended 45 min. or preferably 60 min.

33
Incorporating NAVD88 - Control

• Include reliable NAVD88 marks in the network
• Surround the project (!) with them
• Every 20 km every 3rd network station
• For rugged terrain, control at high and low
  points

34
Notes 2 cm accuracy and other things

• Relative accuracy in ellipsoid heights between
  adjacent points (local accuracy) will be better
  than 2 cm, at 95 confidence level
• Network accuracy (relative to NSRS) in ellipsoid
  and orthometric heights will be better than 5 cm
• Accuracy of orthometric height is dependent on
  accuracy of the geoid model - NGS is improving
  the geoid model with more data, ie, GPS
  observations on leveled bench marks fr Ht Mod
  projects

35
West Virginia
Primary Control CORS
36
Primary Control West Virginia High Accuracy
Reference Network
37
Ellipsoid, Geoid, and Orthometric Heights
H Orthometric Height (leveling)
H h - N
h Ellipsoidal Height (GPS)
N Geoid Height (model)

H (NAD83)
TOPOGRAPHIC SURFACE
(NAVD88) H
N
Geoid Height (GEOID03)
Ellipsoid
Geoid
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Definitions GEOIDS versus GEOID HEIGHTS

• The equipotential surface of the Earths gravity
  field which best fits, in the least squares
  sense, (global) mean sea level.
• Cant 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 height from an ellipsoid 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

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Types and Uses of Geoid Height Models

• Gravimetric (or Gravity) Geoid Height Models
• Defined by gravity data
• Refined by terrain models (DEMs)
• Usually uses most recent ellipsoid datum (ITRF)
• USGG2003, USGG2008, etc.
• Scientific and engineering applications
• Composite (or Hybrid) Geoid Height Models
• Gravimetric geoid defines most regions
• Warped to fit available GPSBM control data
• Defined by legislated ellipsoid (NAD 83) and
  local vertical datum (NAVD 88, PRVD02, etc.)
• GEOID03, GEOID06, etc.
• Statutory for most surveying mapping
  applications

40
Gravity Observations

• Most of the historical NGS data is terrestrial
• Multiple observers, multiple processors over the
  past 60 years
• Numerous corrections and datums over time
• Metadata maintained in paper records
• Very limited aerogravity

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Gravity Coverage for USGG2003/USGG2008
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Gravimetric v s. Hybrid Geoid surface

Earths Surface
Ellipsoid
N
N
N
Hybrid Geoid
N
0.956 M in Charleston, WV 1999 model
0.999 M in Charleston, WV 2003 model
Gravimetric Geoid

• Gravimetric Geoid systematic misfit to BMs but
  best fits true heights
• Hybrid Geoid converted to fit local BMs, so
  best fits NAVD 88 heights
• Conversion Surface model of systematic misfit
  derived from BMs in IDB

44
GGPSBM1999 6,169 total 0 Canada STDEV
9.2 cm (2s)
GGPSBM2003 14,185 total 579 Canada STDEV 4.8
cm (2 s)
GPSBM2007 18,609 total 579 Canada STDEV
5.8 cm (2 s)
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NGS Datasheet Leveling/GPS

• 1 National Geodetic Survey, Retrieval
  Date JUNE 8, 2008
• HX2192
  
• HX2192 CBN - This is a Cooperative
  Base Network Control Station.
• HX2192 DESIGNATION - 192 JJS
• HX2192 PID - HX2192
• HX2192 STATE/COUNTY- WV/LINCOLN
• HX2192 USGS QUAD - GRIFFITHSVILLE (1976)
• HX2192
• HX2192 CURRENT SURVEY
  CONTROL
• HX2192 _________________________________________
  __________________________
• HX2192 NAD 83(2007)- 38 14 19.27170(N) 081
  59 24.03133(W) ADJUSTED
• HX2192 NAVD 88 - 203.375 (meters)
  667.24 (feet) ADJUSTED
• HX2192 _________________________________________
  __________________________
• HX2192 EPOCH DATE - 2002.00
• . . .
• HX2192 LAPLACE CORR- 0.84 (seconds)
  DEFLEC99
• HX2192 ELLIP HEIGHT- 170.378 (meters)
  (02/10/07) ADJUSTED
• HX2192 GEOID HEIGHT- -32.99 (meters)
  GEOID03
• HX2192 DYNAMIC HT - 203.231 (meters)
  666.77 (feet) COMP

46
NGS Datasheet Leveling/GPS

• HX2192.The horizontal coordinates were
  established by GPS observations
• HX2192.and adjusted by the National Geodetic
  Survey in February 2007.
• HX2192
• HX2192.The datum tag of NAD 83(2007) is
  equivalent to NAD 83(NSRS2007).
• HX2192.See National Readjustment for more
  information.
• HX2192.The horizontal coordinates are valid at
  the epoch date displayed above.
• HX2192.The epoch date for horizontal control is
  a decimal equivalence
• HX2192.of Year/Month/Day.
• HX2192
• HX2192 The orthometric height was determined by
  differential leveling
• HX2192 and adjusted in June 1991.
• HX2192
• HX2192.The X, Y, and Z were computed from the
  position and the ellipsoidal ht.
• HX2192
• HX2192.The Laplace correction was computed from
  DEFLEC99 derived deflections.
• HX2192
• HX2192 The ellipsoidal height was determined by
  GPS observations
• HX2192 and is referenced to NAD 83.
• HX2192

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NGS Datasheet Leveling/GPS

• HX2192
• HX2192 North East
  Units Scale Factor Converg.
• HX2192SPC WV S - 137,942.890
  513,335.742 MT 0.99992612 -0 36 43.3
• HX2192SPC WV S - 452,567.63 1,684,169.01
  sFT 0.99992612 -0 36 43.3
• HX2192UTM 17 - 4,232,761.640
  413,361.341 MT 0.99969244 -0 36 46.1
• HX2192
• HX2192! - Elev Factor x Scale
  Factor Combined Factor
• HX2192!SPC WV S - 0.99997327 x
  0.99992612 0.99989939
• HX2192!UTM 17 - 0.99997327 x
  0.99969244 0.99966571
• HX2192
• HX2192 SUPERSEDED
  SURVEY CONTROL
• HX2192
• HX2192 NAD 83(1995)- 38 14 19.27207(N) 081
  59 24.03143(W) AD( ) A
• HX2192 ELLIP H (04/23/01) 170.367 (m)
  GP( ) 4 1
• HX2192 NAVD 88 (04/23/01) 203.38 (m)
  667.3 (f) LEVELING 3
• HX2192 NGVD 29 (??/??/92) 203.586 (m)
  667.93 (f) ADJ UNCH 2 0
• HX2192
• HX2192.Superseded values are not recommended for
  survey control.
• HX2192.NGS no longer adjusts projects to the NAD
  27 or NGVD 29 datums.

48
NGS Datasheet Leveling/GPS

• HX2192_STABILITY C MAY HOLD, BUT OF TYPE
  COMMONLY SUBJECT TO
• HX2192STABILITY SURFACE MOTION
• HX2192_SATELLITE THE SITE LOCATION WAS REPORTED
  AS SUITABLE FOR
• HX2192SATELLITE SATELLITE OBSERVATIONS -
  December 14, 2004
• HX2192
• HX2192 HISTORY - Date Condition
  Report By
• HX2192 HISTORY - 1956 MONUMENTED
  USGS
• HX2192 HISTORY - 1957 GOOD
  NGS
• HX2192 HISTORY - 20000323 GOOD
  WVALS
• HX2192 HISTORY - 20021120 GOOD
  INDIV
• HX2192 HISTORY - 20021120 GOOD
  INDIV
• HX2192 HISTORY - 20040519 GOOD
  NGS
• HX2192 HISTORY - 20041214 GOOD
  INDIV
• HX2192
• HX2192 STATION
  DESCRIPTION
• HX2192
• HX2192'DESCRIBED BY NATIONAL GEODETIC SURVEY
  1957
• HX2192'0.2 MI E FROM GRIFFITHSVILLE.
• HX2192'ABOUT 0.2 MILE EAST ALONG STATE HIGHWAY 3
  FROM THE HIGH SCHOOL

49
NGS Datasheet NAVD 88 GPS

• AJ2508
  
• AJ2508 CBN - This is a Cooperative
  Base Network Control Station.
• AJ2508 DESIGNATION - ELKVIEW
• AJ2508 PID - AJ2508
• AJ2508 STATE/COUNTY- WV/KANAWHA
• AJ2508 USGS QUAD - BLUE CREEK (1995)
• AJ2508
• AJ2508 CURRENT SURVEY
  CONTROL
• AJ2508 _________________________________________
  __________________________
• AJ2508 NAD 83(2007)- 38 27 24.52196(N) 081
  29 45.18827(W) ADJUSTED
• AJ2508 NAVD 88 - 192.4 (meters)
  631. (feet) GPS OBS
• AJ2508 _________________________________________
  __________________________
• AJ2508 EPOCH DATE - 2002.00
• AJ2508 X - 739,576.221 (meters)
  COMP
• AJ2508 Y - -4,946,190.352 (meters)
  COMP
• AJ2508 Z - 3,945,375.378 (meters)
  COMP
• AJ2508 LAPLACE CORR- 2.43 (seconds)
  DEFLEC99
• AJ2508 ELLIP HEIGHT- 159.257 (meters)
  (02/10/07) ADJUSTED
• AJ2508 GEOID HEIGHT- -33.10 (meters)
  GEOID03

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Height Mod GPS Datasheet

• 1 National Geodetic Survey, Retrieval
  Date JANUARY 4, 2008
• DH5603
  
• DH5603 HT_MOD - This is a Height
  Modernization Survey Station.
• DH5603 DESIGNATION - ALTO S GPS
• DH5603 PID - DH5603
• DH5603 STATE/COUNTY- WI/FOND DU LAC
• DH5603 USGS QUAD - BRANDON (1980)
• DH5603
• DH5603 CURRENT SURVEY
  CONTROL
• DH5603 _________________________________________
  __________________________
• DH5603 NAD 83(2007)- 43 38 45.90850(N) 088
  49 31.20449(W) ADJUSTED
• DH5603 NAVD 88 - 283.45 (meters)
  930.0 (feet) GPS OBS
• DH5603 _________________________________________
  __________________________
• DH5603 EPOCH DATE - 2002.00
• DH5603 X - 94,770.713 (meters)
  COMP
• DH5603 Y - -4,621,912.764 (meters)
  COMP
• DH5603 Z - 4,379,891.970 (meters)
  COMP
• DH5603
• DH5603

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Height Mod GPS Datasheet

• 1 National Geodetic Survey, Retrieval
  Date JANUARY 4, 2008
• DH5603
  
• DH5603 HT_MOD - This is a Height
  Modernization Survey Station.
• DH5603 DESIGNATION - ALTO S GPS
• DH5603 PID - DH5603
• DH5603 STATE/COUNTY- WI/FOND DU LAC
• DH5603 USGS QUAD - BRANDON (1980)
• DH5603
• DH5603 CURRENT SURVEY
  CONTROL
• DH5603 _________________________________________
  __________________________
• DH5603 NAD 83(2007)- 43 38 45.90850(N) 088
  49 31.20449(W) ADJUSTED
• DH5603 NAVD 88 - 283.45 (meters)
  930.0 (feet) GPS OBS
• DH5603 _________________________________________
  __________________________
• DH5603 EPOCH DATE - 2002.00
• DH5603 X - 94,770.713 (meters)
  COMP
• DH5603 Y - -4,621,912.764 (meters)
  COMP
• DH5603 Z - 4,379,891.970 (meters)
  COMP
• DH5603 LAPLACE CORR- -0.16 (seconds)
  DEFLEC99
• DH5603 ELLIP HEIGHT- 247.946 (meters)
  (02/10/07) ADJUSTED

H

h

N
NAVD88 Ellipsoid Ht Geoid Ht 283.45
247.946 35.730 -0.226 USGG2003 283.45
247.946 35.476 0.028 GEOID03
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GRAV-D Gravity for the Redefinition of the
American Vertical Datum

• Official NGS policy as of Nov 14, 2007
• 38.5M over 10 years
• Airborne Gravity Snapshot
• Absolute Gravity Tracking
• Re-define the Vertical Datum of the USA by 2017

53
Airborne Meter
Initial road tests (Nov 2007)
First build (Oct 2007)

• Unit is TAGS (Turn-key Airborne Gravity System)
• Sensor, Software and Training sold as a package
  from Micro-G/LaCoste
• Has been flight tested and proven as the most
  accurate airborne meter available

54
Gravity Survey Plan

• Airborne
• Critically needed as a one-time high resolution
  snapshot of gravity in the USA
• As opposed to the thousands of surveys, with
  hundreds of instruments and operators over dozens
  of years
• One time survey
• Absolute
• Cyclical for episodic checks in fixed locales
• Co-incident with foundation CORS?
• Two field meters plus one fixed SG
• Relative
• More frequently attached to Height Mod surveys

55
Ross Mackay Kentucky Geodetic Advisor
NOAA's National Geodetic Survey Height
Modernization In Kentucky
2008 West Virginia GIS Conference June 12, 2008
56
Height Modernization in Kentucky
57
Height Modernization in Kentucky
In most parts of the state, 50 percent or more of
all bench marks have been destroyed due to
construction and land development activities. A
Long-Range Plan for Height Modernization in
Wisconsin Improving the Vertical Component of
the Geodetic Network 2003
Cumberland County - 2004
58
Height Modernization in Kentucky
10,461 benchmarks remain in NGS database
20 reported not found or in poor condition
23 reported as good in last 25 years
Only 12 reported as good in last 10 years
59
Height Modernization in Kentucky
Congressman Hal Rogers October 25, 2004
"I am pleased to announce today that Kentucky
will receive funding for Height Modernization in
NOAAs fiscal 05 budget."
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Height Modernization in Kentucky

• Morehead State University
• Grant recipient from NOAA
• Submit application and project reports for Grant
• Develop Kentucky CORS Data Archive Center
• KY Division of Geographic Information
• Provide overall Height Modernization project
  management
• Develop project charters, plans and agreements
• Kentucky Transportation Cabinet
• Install and provide ongoing support of CORS sites
• Manage the award of contracts and oversight of
  the work

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Height Modernization in Kentucky
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Height Modernization in Kentucky

• Morehead, KYMH
• Cumberland, KYCB
• Somerset, KYSC
• Campbellsville, KYCB
• Taylor Lake, Lou5
• Ashland, KYAS
• Madisonville , KYTB
• Bowling Green, KYTC
• Elizabethtown, KYTD
• Louisville, KYTE
• Covington, KYTF
• Lexington, KYTG
• Somerset, KYTH
• Flemingsburg, KYTI
• Manchester, KYTK
• Pikeville, KYTL

• Greenbo Lake SRP, KYGB
• Dale Hollow SRP, KYDH
• Rough River SRP, KYRR

• Paducah, KYTA
• Jackson, KYTJ

• Elizabethtown, KYTD

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Height Modernization in Kentucky
Some things never change
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Height Modernization in Kentucky
But they do get digital.
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Ross Mackay Kentucky Geodetic Advisor
ross.mackay_at_ky.gov on the web at ngs.ky.gov (502
) 564-1474
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NGS Business Plan Three Areas of Focus

• Infrastructure
• Models and Tools
• Outside Capacity Building

67
Infrastructure

• Define, maintain, provide access to NSRS
• Active control network CORS
• Passive control network as needed
• Guidelines and standards for geodetic field and
  processing practices
• Quality check data that is incorporated in the
  NGS database
• Enable positioning consistent with NSRS

68
Published Height Modernization Stations
69
Models and Tools

• Modeling atmospheric, 1-cm geoid
• Development of software, tools
• Software, Online Tool Kit
• OPUS Variety Pack
• Field tools PGM, Digital Level Tool
• VDatum
• Guidelines for use of new technologies and
  processes like remote sensing, real time

70
Guidelines
Available On-Line at the NGS Web
Site www.ngs.noaa.gov/PUBS_LIB/pub_index.html
71
Level Tool under development at TAMUCC
72
Outside Capacity Building

• State Geodetic Advisor Program
• Forums, workshops
• Conferences
• Publications, web site
• Training, capacity building

73
www.ngs.noaa.gov/heightmod
74
Capacity Building
Training center in Corbin, VA
Leveling Spokane, 2006
www.ngs.noaa.gov/corbin/index.shtml
75
www.wvsps.org
76
Accomplishments Building Partnerships

• State Agencies - NCGS, SCGS, WiDOT, ALDOR,
  WADNR, AZSLD
• Spatial Reference Centers CA, LA, WA, TX, AZ
• Universities Scripps, LSU, USM, TAMUCC, NCAT,
  Morehead State
• NOAA and other Federal Agencies USACE, USGS,
  FEMA

77
www.ncfloodmaps.com
Results of partnerships
Link to Digital Flood Maps
78
Results of partnerships

• FEMA Map Modernization, Post-Katrina recovery
  project

79

• Role of NGS Program Management
• Congressional briefings
• Budget, grants management
• Coordination Partners, SRCs
• Role of NGS Project Leadership
• Support program growth - develop long range plan
• Support advance of science
• Support NOAAs Mission shoreline, weather,
  climate change

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A National Program

• Needs dont stop at state boundaries
• States within a region work in concert to support
  common issues/goals
• More efficient use of funds, people
• Encourages partnerships
• Congress more likely to continue funding for
  programs that impact a larger area/group of
  constituents commitment to program on part of
  users

81
Height Modernization Regions
82
Height Mod Objectives

• Consistent, accurate vertical AND horizontal
  control network
• Passive GPS-able network today
• Active maintainable network tomorrow
• Build capacity in the surveying community to
  perform the surveys and properly use the data
• Provide data to build better models (DEMs, geoid,
  storm surge) and products (FIRMs)
• Provide access to NSRS to enable expansion of
  applications, like RTK, GIS

83
Should anyone lose sight of why NGS cares about
knowing and maintaining accurate heights
84
Questions
Contact information
Renee Shields Height Modernization
Manager N/NGS1, SSMC3, Room 9357 1315 East-West
Highway Silver Spring, MD 20910 301-713-3231,
x116 Renee.Shields_at_noaa.gov
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20-100 km gravity gaps along coast
Terrestrial gravity
New Orleans
Ship gravity
86
GRAV-D Campaign IPhase I, Part 1 - Testing

• Test varieties of flight heights / speeds /
  spacings for optimal ratio of
• g-accuracy
• Data have been collected and are being analyzed

87
GRAV-D Campaign IPhase I, Part 2 - Testing

• Test area for proof of concept to define vertical
  datum from GPS gravimetric geoid
• PR/VI cost would run 300k
• Likely deferred until Fall to allow analysis

88
Gravity Survey Plan Phase II - Operations

• In a carefully chosen order

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Fast, Accurate Orthometric Heights

• GPS already gives fast accurate ellipsoid heights
• If the geoid were determined to highest accuracy
• Voila Fast, accurate orthometric heights