1. Coordination of Federal Geospatial Work: The National Spatial Reference System
Juliana Blackwell, Director
National Geodetic Survey, NOAA
February 2, 2010

2. NGS’s Role and Authority vis-à-vis “The NSRS”
OMB Circular A-16 (revised):
Names DOC and NOAA as “lead agency” for Geodetic Control, and says:
“All NSDI framework data and users' applications data require geodetic control to accurately register spatial data.”
“The National Spatial Reference System is the fundamental geodetic control for the United States.”
The OMB circular A-16 is one of the clearest documents, outlining the roles of the multiple civilian mapping authorities. Both USGS and USACE should know their roles in this.
Last Updated 30 Nov 2009 (DAS)

3. NGS Mission Statement
To define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation’s economic, social, and environmental needs.
The Earth is an irregular surface and is hard to model
Geodesy (geodetic control) defines position & height

4. National Spatial Reference System (NSRS)
The NSRS is a consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation throughout the United States. It includes the current datums NAD 83 and NAVD 88. 

5. NGS Provides the Geospatial Foundation for a Wide Variety of Activities
Geodetic Control
Aerial Imagery
Elevation
Boundaries
Surface Waters
Transportation
Land Ownership

6. FGCS-issued Federal Register Notices Regarding NSRS Use
Use of the NAD 83 / WGS 84 Datum Tag on Mapping Products (August 14, 1995) (
Affirmation of Datum for Surveying and Mapping Activities (June 13, 1989; NAD83)
Affirm North American Datum of 1983 (NAD 83) as the official horizontal datum for all U.S. surveying and mapping activities performed or financed by the federal government. (
Affirmation of Vertical Datum for Surveying and Mapping Activities (June 23, 1993; NAVD88)
Affirms North American Vertical Datum of 1988 (NAVD 88) as the official civilian vertical datum for surveying and mapping activities in the United States performed or financed by the Federal Government. (
“To the extent practicable, legally allowable, and feasible, require that all Federal agencies using or producing vertical height information undertake an orderly transition to NAVD 88.”

7. Horizontal Datum – NAD 83 Vertical Datum - NAVD 88
The North American Datum of 1983 (NAD 83) is the current horizontal control datum.
Vertical Datum - NAVD 88
This exemplifies the history of how we’ve done vertical datums (through passive marks) and the difficulty of continuing that method of doing business. Collectively, there are over 1.5 million control marks in the ground.
The North American Vertical Datum of 1988 (NAVD 88) is the current vertical control datum.

8. Why aren’t NAD 83 (horizontal) and NAVD 88 (vertical) good enough anymore?
Differential GPS positioning (from CORS) has made access to latitude and longitude fast and accurate, removing the need to define the datum through passive control.
NAD 83 was defined in a pre-GPS era, resulting in a 2.2 meter non-geocentricity relative to ITRF – this translates to -2 to +2 meter errors in latitude, longitude and ellipsoid height around the global territories of the USA.
The GPS era brought fast, accurate ellipsoid heights –
naturally this drove a desire for fast, accurate
orthometric heights.
Leveling the country cannot be done again.
Too costly in time and money.
Yields cross-country errors.
Relies on a fragile, unmonitored, poorly distributed set of passive marks.

9. Constant monitoring of position and height is important because the Earth constantly changes
Benchmark set at .2m (1980)

10. Continuously Operating Reference Stations (CORS)
Grows by ~200 new stations a year.

11. USACE Levee Inventory
Working with USACE to utilize a common datum (NAVD 88) on all 12,000 miles of levees.
Advocating the use of VDatum for accurate water levels and geodetic data.
Writing procedures for obtaining heights at various accuracy needs.
Developing training materials for USACE personnel.
OPUS-DB will allow USACE to see historical GPS solutions (and thus monitor changes) over time.
Courtesy of Tulane University
Writing procedures for various accuracy levels:
In areas where there’s less of a need for high accuracy – ‘stable’ areas – the requirement can be as low as 8 cm. In these cases they will use OPUS-DB.
In areas of subsidence or other natural phenomenon where high accuracy is needed, they must use Height Mod guidelines
Dave Doyle will be giving training seminar soon
Benchmark set at .2m (1980)

12. Replacing NAVD 88: GRAV-D
Why Change?
The Earth’s crust is in constant motion displacing the positions of many vertical bench marks (NAVD 88).
- Benchmarks set in the ground move with the ground.
- Finding an old benchmark might be worse than not finding it, if the “known” (published) elevation hasn’t been updated.
GPS derived heights (ellipsoid heights) only provide half of the picture. High accuracy gravity data is needed to determine the geoid (geoid undulation – the other half).
Gives users a starting orthometric height from GNSS anywhere (without finding an inconvenient, unmonitored passive mark), from which leveling and mapping may be conducted.
“Only gravity knows where water flows!”
San Joaquin Valley subsidence

13. Gravity for the Redefinition of the American Vertical Datum (GRAV-D)
Airborne gravity survey (10 years)
Geoid monitoring into the future
Coastal areas surveyed first
All USA states and territories
Goals:
Orthometric heights good to 2 cm anywhere, anytime from GNSS technology
Height changes easily monitored using new vertical datum expected to be complete around 2022.
Implementation:
GRAV-D requires $6M / year to be complete by 2018
FY 2010 funding - $3.5M
Seeking collaboration with 7 other federal agencies with a stake in GRAV-D.
Need to work on transitioning to a benchmark-free customer base (including USACE and USGS)
GRAV-D needs funding, and NGS is seeking it through NOAA’s internal funding channels. Unfortunately, no official funding has so far been designated, and all GRAV-D flights have been either out of NGS base funds or through one time partnerships.
NGS would prefer that other federal partners join GRAV-D, as the number of partners in a project will increase the likelihood of gaining NOAA funding. Nonetheless, even with no partners and no additional funding, NGS is pursuing GRAV-D as the right thing to do for updating NAVD 88. Unfortunately, out of base funds, this may take 50 years.
In addition to seeking FEMA as a partner, NGS wishes to set up a pilot project with them where we provide preliminary tools that would allow a floodplain map to be generated in a benchmark-free environment. This should help the user community more easily transition to the new datum when it is finally changed.
Sent 7 letters to:
NGA
USGS
FAA
USACE
FEMA
ONR
NASA

14. What is the status of GRAV-D?
NGA funded;
NRL plane
As of January 2010
6.7% of planned
areas have been
flown
So far: Gulf coast from Fla to Mexican border ; Puerto Rico and the Virgin Islands ; Anchorage ; Fairbanks.
USACE funded

15. Federal Geospatial Summit
On proposed improvements to the NSRS:
Replacing NAD 83 and NAVD 88
Date: May 11-12, 2010
Location: NOAA Science Center, Silver Spring, MD
Goals:
Disseminate the rationale leading to the decision to modernize the horizontal and vertical geodetic datums.
Exchange information on the plans and methodologies to modernize the geometric and geopotential datums of the NSRS.
Share concerns on how the replacement of these two datums will impact the user community.
Outline future tasks which must be accomplished for the successful redefinition of the horizontal and vertical datums.
Participants: All federal partners

16. VDatum: Vertical Datum Transformation Tool
VDatum is a software tool capable of transforming coastal bathymetry and land topographic elevations between 36 different vertical datums. 

17. Additional Information
The NGS 10 year plan ( )
The GRAV-D Project
Socio-Economic Benefits of CORS and GRAV-D
Last Updated 30 Nov 2009 (DAS)

18. Thank you