GPS and Geodetic News You Can Use

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GPS and Geodetic News You Can Use
David Conner Geodetic Advisor to the State of
Ohio National Geodetic Survey, NOAA
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TOPICS

• Overview
• National Readjustment - NAD83 (NSRS2007)
• GPS CORS, OPUS, OPUS-DB, and more
• County Scorecard

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National ReadjustmentNAD83 (NSRS2007)

• NGS has just completed a major Readjustment to
  the National Spatial Reference System (NSRS).
• Updated all GPS survey control point positions in
  North America.
• Resolved coordinate inconsistencies between CORS
  and monumented control
• New accuracy Standards for Geodetic Control will
  be implemented

• The CEAO Board, on Sept 6, 2007, passed a
  resolution to Adopt NAD83 (NSRS2007) as the
  reference system of choice for the development of
  county coordinate systems in Ohio.

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Shifts in Ohio

• NAD 83 (1995) vs NAD 83 (NSRS2007)
• Horz Shift Average 0.016 m (Max 0.348 m)
• Vert Shift Average 0.013 m (Max 0.503 m)

Example actual horizontal shifts at station SMITH
(JY0742) NAD 27 vs NAD 83 (1986) 13
meters NAD 83 (1986) vs NAD 83 (1995) 20 cm
NAD 83 (1995) vs NAD 83 (NSRS2007) 1.5 cm
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For Stations not IncludedIn the NSRS (2007)
readjustment

• NGS recommends that NAD 83 data that is not part
  of the NSRS readjustment be readjusted using
  original observation data
• Because of the relatively small shifts involved
  transformation software such as NADCON will not
  be developed for NAD 83(NSRS2007)
• NADCON accuracy 6 cm (0.2 ft)
• NAD 83 (NSRS2007) avg shift 2.5 cm
• NGS will streamline the process of project
  acceptance
• OPUS DB coming soon - ?

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Ohios GPS CORS Network
Brought to you courtesy of the ODOT, Bureau of
Aerial Engineering VRS/ CORS information
Telephone [phone], or 614-351-2839.
cors_at_dot.state.oh.us
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CORS/OPUS Overview Status
CORS Continuously Operating Reference Station
The CORS network contains about 1,250 GPS
tracking stations, and it is growing by about 200
stations per year. OPUS is a Web-based service
enabling users to automatically post-process GPS
data.
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Vertical standard error achievable when a user
submits 15 minutes of GPS data to OPUS-RS
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OPUS FLAVORS
Try it http//beta.ngs.noaa.gov/CORS-Proxy/oraOp
usDbWeb/
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OPUS-DB
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OPUS-DBSample Datasheet
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OPUS ? Datasheet Concept
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GPS data requirements
OPUSable 4 hours of dual frequency data
NGS-calibrated antenna OPUS must achieve 70
observations used 70 ambiguities fixed
0.04m peak-to-peak horizontal 0.08m
peak-to-peak vertical 0.03m RMS
GPS data
(4hr, good stats)
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metadata requirements
control station description
control stationphoto
antenna type, height
optional for existing stations.
Simplified bluebooking
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NOAAS County Scorecard

• NOAA has a relatively new performance metric that
  assesses how well we are doing at enabling
  local capacity for accurate positioning. This
  metric
• Makes use of NOAAs Online Positioning User
  Service (OPUS) as a proxy to assess the local use
  of NOAA positioning tools and services. Was
  developed over the past several years in
  partnership with National Association of County
  Surveyors (NACS).
• Involves the use of a web-based county scorecard
  of 23 survey questions specifically focusing on
  infrastructure, NGS models and tools, NGS
  capacity building and outreach, and overall
  satisfaction.
• We need input from YOU, our core customers, to
  help NOAA improve its geospatial products and
  services.
• For more information, visit http//www.ngs.noaa.go
  v/scorecard/
• or contact
• Your NOAA State Geodetic Advisor, in Ohio
  Dave.Conner_at_noaa.gov
• (for current list of all Advisors visit
  http//www.ngs.noaa.gov/ADVISORS/)
• OR
• Brett Howe (Brett.Howe_at_noaa.gov)

We want YOU to tell us how were doing
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Our Performance Metric Asks
County Scorecard Details

• Are Counties using NOAAs positioning products
  and services?
• NOAA looks at County Online Positioning User
  Service (OPUS) use as a proxy. Have there been
  25 or more OPUS solution generations in a given
  county in the last 12 months?
• Counties meeting the above criteria are
  substantially enabled (shaded yellow).
• Is there feedback and interaction between the
  local community and NOAA?

• Is the County in a State that participates in the
  NOAA State Advisor/Coordinator program?
• Has a County Geospatial Representative been
  identified (eg County Surveyor, County Engineer,
  GIS Administrator, or equivalent)?
• Has blue book data from the County been
  submitted to NGS through activities such as
  leveling project software, GPS projects and OPUS
  DB (when available)?
• Has a County Scorecard web survey been filled out
  by the County Geospatial Representative?
• Counties meeting the above criteria are fully
  enabled (shaded green).

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NOAAS County ScorecardHow you can help
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NSRS Coordinate Systems

• Latitude Longitude
• State Plane Coordinates
• UTM Coordinates
• U.S. National Grid
• Earth-Centered Earth-Fixed
• NAD 83
• NAD 27
• NAVD 88
• NGVD 29
• ITRF00
• ITRF05

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• Coordinate Confusion

DATUM TAGS are the following all the
same? NAD_83(CORS96) NAD 83 (CORS) NAD_83
Position (EPOCH 2002.0) NAD_83(CORS96)
(EPOCH2002.0000) NAD83 (NSRS2007) NAD 83
(2007) WGS_84(original) WORLD GEODETIC SYSTEM
1984 how many WGS84s have there been?
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• Whats A Person To Do?

• USER BEWARE software is suspect re datums and
  conversions
• HTDP use it to test coordinates
• http//www.ngs.noaa.gov/TOOLS/program_description
  s.htmlHTDP
• FUTURE
• NGS will provide simple transformation tools
  between datums and reference frames used by NGS
• HTDP will evolve to include vertical
  transformations TDP

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HTDP NAD_83(CORS96) to WGS-84(original)
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HTDPNAD_83(CORS96) to WGS-84(original)
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The NGS 10 year plan
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Q What is GRAV-D?A A Plan (released Dec 2007)

• Gravity for the Re-definition 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

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Q What is GRAV-D?A Gravity to determine
heights accurately

• The first, middle and last point of GRAV-D
• Gravity and Heights are inseparably connected
• Or (to borrow from a common bumper sticker)
• No gravity, no height
• Know gravity, know height
• http//www.ngs.noaa.gov/GRAV-D/

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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
• Anywhere in the nation
• Time-changes to H determined through
• GPS on CORS (h changes)
• Absolute gravity spot checks (N changes)

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GRAV-D

• Airborne gravity
• 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 gravity
• Cyclical for episodic checks in fixed locales
• Co-incident with foundation CORS?
• Two field meters plus one fixed SG
• Relative Gravity
• More frequently attached to Height Mod surveys

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National Readjustment
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National Readjustment
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New Standards for Geodetic Control

• Local accuracy ----------- Relative to Adjacent
  Points
• Network Accuracy ------- Relative to CORS
• Both are relative accuracy measures at 95
  confidence
• Will not use distance dependent (proportional)
  expression of accuracy Order/Class codes (A, B,
  1, etc.)

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Example Datasheet with new Accuracies
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FGDC Standards for Geodetic Control
http//www.fgdc.gov/standards
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Future Changes?

• The published CORS coordinates based on ITRF2000
  define the new NAD 83 (NSRS2007) coordinate
  system
• When the next version of ITRF is available NGS
  will probably adopt it and revise the CORS
  coordinates within a couple of years

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OPUS-RS Accuracy for 15-minute data sets