Update on NGS Activities ftp://ftp.ngs.noaa.gov/pub/marti Marti Ikehara California Geodetic Advisor, Sacramento

Outline Recap of Products and Services New datums to be defined (decade) GRAV-D Program, building on GOCE data New datum, epoch for CORS (months) Visualizing Geodetic control Planning tools for Sea Level Rise

Products and Services CONTROL: Datasheets for passive monuments; Data for/from CORS, 24/7 OPUS Processing: Simple way to tie to NSRS; results within minutes – Single point, single obs data can be ‘published’ – Working toward OPUS-Database for multiple points Glitch: Wrong accuracy for ortho from 3/10-9/10 Software tools: HTDP, VERTCON, VDATUM, Inverse, SPC, web-map-based retrievals Services: CBLs, Workshops/Training webinars

What IS a datum? It is a reference, a basis, for coordinates, so a datum has an origin and/or ‘zero’. “Underlying” a horizontal datum system is an ELLIPSOID, that represents the global shape of the earth; a DATUM is the ‘continental’ shape as realized with physical marks (passive or active) Our vertical datum is based on continental-scale differential leveling; is lacking or nonexistent in many places, and over 22 years old, getting older

EQUIPOTENTIAL SURFACES

Rationale for new Datums Terminology – Horizontal becomes GEOMETRIC – Vertical becomes GEOPOTENTIAL When?2020+, or when GRAV-D program is completed Why? But why?! 1.Primarily need a better vertical datum for “vertical” data(geoid, ortho ht) not obtained by traditional leveling

2009 National Research Council Report “…uniform national standards for FEMA flood maps cannot be met until an improved orthometric height datum and geoid model exist…”

Rationale for new Datums Terminology – Horizontal becomes GEOMETRIC – Vertical becomes GEOPOTENTIAL When?2018, if GRAV-D program is complete Why? But why?! 1.Primarily need a better vertical datum for “vertical” data(geoid, ortho ht) not obtained by traditional leveling 2.Geodetic Data collection relies upon navigation (GNSS) satellites orbiting around the mass center of the Earth – NAD83 reference frame/datum is not geocentric

Simplified Concept of NAD 83 vs. ITRF00 (or WGS84) 2.2 meters NAD 83 Origin ITRF 00 Origin Earth’s Surface h 83 h 00 Identically shaped ellipsoids (GRS80) a = 6,378, meters (semi-major axis) 1/f = (flattening)

Rationale for new Datums Terminology – Horizontal becomes GEOMETRIC – Vertical becomes GEOPOTENTIAL When?2018, if GRAV-D program is complete Why? But why?! 1.Primarily need a better vertical datum for “vertical” data(geoid, ortho ht) not obtained by traditional leveling 2.Geodetic Data collection relies upon navigation (GNSS) satellites orbiting around the mass center of the Earth – NAD83 reference frame/datum is not geocentric 3.Earth is not stable in all directions; reference frame must account for this to be as geodetically accurate as possible – Vertical velocities are not incorporated in NAD83

H + H t + V E + V Et ITRF00 ( ) Evolution of Geodetic Datums: from NAD27/NGVD29 to NAD83/NAVD88 to ?/ ? H + V , 29 H + V (86), 88 H + V E + V O (92), 88 GPS +VELOCITIES (time) H + H t + V E + V O (07)+HTDP, 88 + GRAVITY (geoid model) H + H t + V E + V Et GEOMETRIC (V E +G)[+V Et ] + G t GEOPOTENTIAL

Gravity/geoid as measured by GOCE satellite

1. Earth is a slightly flattened sphere - it is ellipsoidal in shape 2. Goce senses tiny variations in the pull of gravity over Earth 3. The data is used to construct an idealised surface, or geoid 4. It traces gravity of equal 'potential'; balls won't roll on its 'slopes' 5. It is the shape the oceans would take without winds and currents 6. So, comparing sea level and geoid data reveals ocean behaviour 7. Gravity changes can betray magma movements under volcanoes 8. A precise geoid underpins a universal height system for the world 9. Gravity data can also reveal how much mass is lost by ice sheets

The Future of Height Mod: GRAV-D Gravity for the Redefinition of the American Vertical Datum GRAV-D –Airborne gravity surveys (taking 10 years) –Coastal areas surveyed first –All USA states and territories – GOAL: –Orthometric heights-”elevations” – to be good to 2 cm anywhere, anytime with an excellent ellipsoid height from GNSS technology. Currently *this* takes 3-4 hours at 15-second recording and dual-frequency GPS –Height changes much more easily monitored than by leveling, using new technology – GNSS heights and gravity values –Spot-checking/monitoring gravity changes with portable field units

GEOID09 compared to GEOID03 09: teal, good; yellow: State advisor-rejected; red: analysis-rejected 03 (underlying dots): dk blue, kept; orange: rejected

From Helmer’s article in Winter 09/10 issue of California Surveyor

New datum, epoch for CORS Current: ITRF2000, Near end of year: ITRF2008, and NAD83 (“CORS96A”), for CORS only No change to passive monumentation, eg, NAD83 (NSRS2007), About 1000 CORS nationwide – Those with >2 years of data – Changes on the order of mm, but a few outliers are showing several decimeters – List will be prepared, showing amount of change

Visualization of NGS Geodetic Control Geodetic advisor website, located at Caltrans Office of Land Surveys webpages /geodetic – Google Maps online – Shapefiles – Google Earth kmls DSWorld, NGS partner software

/geodetic/geodetic_control.html

Kml’s and shapefiles downloadable

Using NGS DSWORLD software and Google Earth to get any vintage geodetic data from NGSIDB Start by downloading “Google earth” at: Click here

Mouse-over the “TOOLS” button Click on “DOWNLOAD PC SOFTWARE” Open the NGS main page at

Click here Click on the link: “User Contributed Software is also available…..”

Next, click on the DSWORLD (Version *.**) link. A “file download” window will appear. Choose to save the file where you can easily find it. It will be a zip file, so you will need to unzip it and then double click on the setup.exe file. That will install the program for you. For additional information or assistance, please contact your NGS State Geodetic Advisor

Improving Vertical Ref System, Humboldt Bay wrt Planning for SLR First order leveling done along Hwy 101 for NAVD88 datum in 1988, and Hwy 255 Tide gage location on North Spit EQ in April, 1992 shook things up Scientists and planners concerned that elevations no longer valid, so developing a proposal to re-measure elevations Tide gage record likely to require a shift for EQ

Anything Else?! ftp://ftp.ngs. ftp://ftp.ngs noaa.gov/pub/marti